1
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Márquez D, Escalera-Fanjul X, El Hafidi M, Aguirre-López B, Riego-Ruiz L, González A. Alanine Represses γ-Aminobutyric Acid Utilization and Induces Alanine Transaminase Required for Mitochondrial Function in Saccharomyces cerevisiae. Front Microbiol 2021; 12:695382. [PMID: 34421848 PMCID: PMC8371705 DOI: 10.3389/fmicb.2021.695382] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 07/05/2021] [Indexed: 11/24/2022] Open
Abstract
The γ-aminobutyric acid (GABA) shunt constitutes a conserved metabolic route generating nicotinamide adenine dinucleotide phosphate (NADPH) and regulating stress response in most organisms. Here we show that in the presence of GABA, Saccharomyces cerevisiae produces glutamate and alanine through the irreversible action of Uga1 transaminase. Alanine induces expression of alanine transaminase (ALT1) gene. In an alt1Δ mutant grown on GABA, alanine accumulation leads to repression of the GAD1, UGA1, and UGA2 genes, involved in the GABA shunt, which could result in growth impairment. Induced ALT1 expression and negative modulation of the GABA shunt by alanine constitute a novel regulatory circuit controlling both alanine biosynthesis and catabolism. Consistent with this, the GABA shunt and the production of NADPH are repressed in a wild-type strain grown in alanine, as compared to those detected in the wild-type strain grown on GABA. We also show that heat shock induces alanine biosynthesis and ALT1, UGA1, UGA2, and GAD1 gene expression, whereas an uga1Δ mutant shows heat sensitivity and reduced NADPH pools, as compared with those observed in the wild-type strain. Additionally, an alt1Δ mutant shows an unexpected alanine-independent phenotype, displaying null expression of mitochondrial COX2, COX3, and ATP6 genes and a notable decrease in mitochondrial/nuclear DNA ratio, as compared to a wild-type strain, which results in a petite phenotype. Our results uncover a new negative role of alanine in stress defense, repressing the transcription of the GABA shunt genes, and support a novel Alt1 moonlighting function related to the maintenance of mitochondrial DNA integrity and mitochondrial gene expression.
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Affiliation(s)
- Dariel Márquez
- Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico, Mexico
| | | | - Mohammed El Hafidi
- Departamento de Biomedicina Cardiovascular, Instituto Nacional de Cardiología Ignacio Chávez, Mexico, Mexico
| | - Beatriz Aguirre-López
- Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico, Mexico
| | - Lina Riego-Ruiz
- División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, México
| | - Alicia González
- Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico, Mexico
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2
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Gratz R, Ahmad I, Svennerstam H, Jämtgård S, Love J, Holmlund M, Ivanov R, Ganeteg U. Organic nitrogen nutrition: LHT1.2 protein from hybrid aspen (Populus tremula L. x tremuloides Michx) is a functional amino acid transporter and a homolog of Arabidopsis LHT1. TREE PHYSIOLOGY 2021; 41:1479-1496. [PMID: 33631788 PMCID: PMC8359683 DOI: 10.1093/treephys/tpab029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
The contribution of amino acids (AAs) to soil nitrogen (N) fluxes is higher than previously thought. The fact that AA uptake is pivotal for N nutrition in boreal ecosystems highlights plant AA transporters as key components of the N cycle. At the same time, very little is known about AA transport and respective transporters in trees. Tree genomes may contain 13 or more genes encoding the lysine histidine transporter (LHT) family proteins, and this complicates the study of their significance for tree N-use efficiency. With the strategy of obtaining a tool to study N-use efficiency, our aim was to identify and characterize a relevant AA transporter in hybrid aspen (Populus tremula L. x tremuloides Michx.). We identified PtrLHT1.2, the closest homolog of Arabidopsis thaliana (L.) Heynh AtLHT1, which is expressed in leaves, stems and roots. Complementation of a yeast AA uptake mutant verified the function of PtrLHT1.2 as an AA transporter. Furthermore, PtrLHT1.2 was able to fully complement the phenotypes of the Arabidopsis AA uptake mutant lht1 aap5, including early leaf senescence-like phenotype, reduced growth, decreased plant N levels and reduced root AA uptake. Amino acid uptake studies finally showed that PtrLHT1.2 is a high affinity transporter for neutral and acidic AAs. Thus, we identified a functional AtLHT1 homolog in hybrid aspen, which harbors the potential to enhance overall plant N levels and hence increase biomass production. This finding provides a valuable tool for N nutrition studies in trees and opens new avenues to optimizing tree N-use efficiency.
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Affiliation(s)
- Regina Gratz
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
| | - Iftikhar Ahmad
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
| | - Henrik Svennerstam
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
| | - Sandra Jämtgård
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
| | - Jonathan Love
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
| | - Mattias Holmlund
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
| | - Rumen Ivanov
- Institute of Botany, Heinrich Heine University, 40225 Düsseldorf, Germany
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3
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Wan Y, Wang Y, Shi Z, Rentsch D, Ward JL, Hassall K, Sparks CA, Huttly AK, Buchner P, Powers S, Shewry PR, Hawkesford MJ. Wheat amino acid transporters highly expressed in grain cells regulate amino acid accumulation in grain. PLoS One 2021; 16:e0246763. [PMID: 33606697 PMCID: PMC7894817 DOI: 10.1371/journal.pone.0246763] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 01/25/2021] [Indexed: 11/18/2022] Open
Abstract
Amino acids are delivered into developing wheat grains to support the accumulation of storage proteins in the starchy endosperm, and transporters play important roles in regulating this process. RNA-seq, RT-qPCR, and promoter-GUS assays showed that three amino acid transporters are differentially expressed in the endosperm transfer cells (TaAAP2), starchy endosperm cells (TaAAP13), and aleurone cells and embryo of the developing grain (TaAAP21), respectively. Yeast complementation revealed that all three transporters can transport a broad spectrum of amino acids. RNAi-mediated suppression of TaAAP13 expression in the starchy endosperm did not reduce the total nitrogen content of the whole grain, but significantly altered the composition and distribution of metabolites in the starchy endosperm, with increasing concentrations of some amino acids (notably glutamine and glycine) from the outer to inner starchy endosperm cells compared with wild type. Overexpression of TaAAP13 under the endosperm-specific HMW-GS (high molecular weight glutenin subunit) promoter significantly increased grain size, grain nitrogen concentration, and thousand grain weight, indicating that the sink strength for nitrogen transport was increased by manipulation of amino acid transporters. However, the total grain number was reduced, suggesting that source nitrogen remobilized from leaves is a limiting factor for productivity. Therefore, simultaneously increasing loading of amino acids into the phloem and delivery to the spike would be required to increase protein content while maintaining grain yield.
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Affiliation(s)
- Yongfang Wan
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Yan Wang
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
- Triticeae Institute, Sichuan Agricultural University, Sichuan, P. R. China
| | - Zhiqiang Shi
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
- National Technology Innovation Center for Regional Wheat Production, Key Laboratory of Crop Physiology, and Ecology and Production in Southern China, Ministry of Agriculture, National Engineering and Technology Center for Information Agriculture, Nanjing Agricultural University, Nanjing, P. R. China
| | - Doris Rentsch
- University of Bern, Molecular Plant Physiology, Bern, Switzerland
| | - Jane L. Ward
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Kirsty Hassall
- Computational and Analytical Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Caroline A. Sparks
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Alison K. Huttly
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Peter Buchner
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Stephen Powers
- Computational and Analytical Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Peter R. Shewry
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
| | - Malcolm J. Hawkesford
- Plant Sciences Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
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4
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Haindrich AC, Ernst V, Naguleswaran A, Oliveres QF, Roditi I, Rentsch D. Nutrient availability regulates proline/alanine transporters in Trypanosoma brucei. J Biol Chem 2021; 296:100566. [PMID: 33745971 PMCID: PMC8094907 DOI: 10.1016/j.jbc.2021.100566] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 03/09/2021] [Accepted: 03/17/2021] [Indexed: 11/23/2022] Open
Abstract
Trypanosoma brucei is a species of unicellular parasite that can cause severe diseases in livestock and humans, including African trypanosomiasis and Chagas disease. Adaptation to diverse environments and changes in nutritional conditions is essential for T. brucei to establish an infection when changing hosts or during invasion of different host tissues. One such adaptation is the ability of T. brucei to rapidly switch its energy metabolism from glucose metabolism in the mammalian blood to proline catabolism in the insect stages and vice versa. However, the mechanisms that support the parasite's response to nutrient availability remain unclear. Using RNAseq and qRT-PCR, we investigated the response of T. brucei to amino acid or glucose starvation and found increased mRNA levels of several amino acid transporters, including all genes of the amino acid transporter AAT7-B subgroup. Functional characterization revealed that AAT7-B members are plasma membrane-localized in T. brucei and when expressed in Saccharomyces cerevisiae supported the uptake of proline, alanine, and cysteine, while other amino acids were poorly recognized. All AAT7-B members showed a preference for proline, which is transported with high or low affinity. RNAi-mediated AAT7-B downregulation resulted in a reduction of intracellular proline concentrations and growth arrest under low proline availability in cultured procyclic form parasites. Taken together, these results suggest a role of AAT7-B transporters in the response of T. brucei to proline starvation and proline catabolism.
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Affiliation(s)
| | - Viona Ernst
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | | | | | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Doris Rentsch
- Institute of Plant Sciences, University of Bern, Bern, Switzerland.
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5
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Growth Inhibition by Amino Acids in Saccharomyces cerevisiae. Microorganisms 2020; 9:microorganisms9010007. [PMID: 33375077 PMCID: PMC7822121 DOI: 10.3390/microorganisms9010007] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 12/17/2022] Open
Abstract
Amino acids are essential metabolites but can also be toxic when present at high levels intracellularly. Substrate-induced downregulation of amino acid transporters in Saccharomyces cerevisiae is thought to be a mechanism to avoid this toxicity. It has been shown that unregulated uptake by the general amino acid permease Gap1 causes cells to become sensitive to amino acids. Here, we show that overexpression of eight other amino acid transporters (Agp1, Bap2, Can1, Dip5, Gnp1, Lyp1, Put4, or Tat2) also induces a growth defect when specific single amino acids are present at concentrations of 0.5-5 mM. We can now state that all proteinogenic amino acids, as well as the important metabolite ornithine, are growth inhibitory to S. cerevisiae when transported into the cell at high enough levels. Measurements of initial transport rates and cytosolic pH show that toxicity is due to amino acid accumulation and not to the influx of co-transported protons. The amino acid sensitivity phenotype is a useful tool that reports on the in vivo activity of transporters and has allowed us to identify new transporter-specific substrates.
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6
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Abstract
We review the mechanisms responsible for amino acid homeostasis in Saccharomyces cerevisiae and other fungi. Amino acid homeostasis is essential for cell growth and survival. Hence, the de novo synthesis reactions, metabolic conversions, and transport of amino acids are tightly regulated. Regulation varies from nitrogen pool sensing to control by individual amino acids and takes place at the gene (transcription), protein (posttranslational modification and allostery), and vesicle (trafficking and endocytosis) levels. The pools of amino acids are controlled via import, export, and compartmentalization. In yeast, the majority of the amino acid transporters belong to the APC (amino acid-polyamine-organocation) superfamily, and the proteins couple the uphill transport of amino acids to the electrochemical proton gradient. Although high-resolution structures of yeast amino acid transporters are not available, homology models have been successfully exploited to determine and engineer the catalytic and regulatory functions of the proteins. This has led to a further understanding of the underlying mechanisms of amino acid sensing and subsequent downregulation of transport. Advances in optical microscopy have revealed a new level of regulation of yeast amino acid transporters, which involves membrane domain partitioning. The significance and the interrelationships of the latest discoveries on amino acid homeostasis are put in context.
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7
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Mara P, Fragiadakis GS, Gkountromichos F, Alexandraki D. The pleiotropic effects of the glutamate dehydrogenase (GDH) pathway in Saccharomyces cerevisiae. Microb Cell Fact 2018; 17:170. [PMID: 30384856 PMCID: PMC6211499 DOI: 10.1186/s12934-018-1018-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 10/29/2018] [Indexed: 12/19/2022] Open
Abstract
Ammonium assimilation is linked to fundamental cellular processes that include the synthesis of non-essential amino acids like glutamate and glutamine. In Saccharomyces cerevisiae glutamate can be synthesized from α-ketoglutarate and ammonium through the action of NADP-dependent glutamate dehydrogenases Gdh1 and Gdh3. Gdh1 and Gdh3 are evolutionarily adapted isoforms and cover the anabolic role of the GDH-pathway. Here, we review the role and function of the GDH pathway in glutamate metabolism and we discuss the additional contributions of the pathway in chromatin regulation, nitrogen catabolite repression, ROS-mediated apoptosis, iron deficiency and sphingolipid-dependent actin cytoskeleton modulation in S.cerevisiae. The pleiotropic effects of GDH pathway in yeast biology highlight the importance of glutamate homeostasis in vital cellular processes and reveal new features for conserved enzymes that were primarily characterized for their metabolic capacity. These newly described features constitute insights that can be utilized for challenges regarding genetic engineering of glutamate homeostasis and maintenance of redox balances, biosynthesis of important metabolites and production of organic substrates. We also conclude that the discussed pleiotropic features intersect with basic metabolism and set a new background for further glutamate-dependent applied research of biotechnological interest.
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Affiliation(s)
- P. Mara
- Department of Chemistry, University of Crete, Voutes University Campus, 71003 Heraklion, Crete Greece
- Present Address: Woods Hole Oceanographic Institution, Woods Hole, MA 02543 USA
| | - G. S. Fragiadakis
- Institute of Molecular Biology & Biotechnology, FORTH, Nikolaou Plastira 100 GR-70013, Heraklion, Crete Greece
| | - F. Gkountromichos
- Department of Biology, University of Crete, Voutes University Campus, 71003 Heraklion, Crete Greece
- Faculty of Biology, Biocenter, Ludwig-Maximilians-University of Munich, Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany
| | - D. Alexandraki
- Department of Biology, University of Crete, Voutes University Campus, 71003 Heraklion, Crete Greece
- Institute of Molecular Biology & Biotechnology, FORTH, Nikolaou Plastira 100 GR-70013, Heraklion, Crete Greece
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8
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André B. Tribute to Marcelle Grenson (1925-1996), A Pioneer in the Study of Amino Acid Transport in Yeast. Int J Mol Sci 2018; 19:E1207. [PMID: 29659503 PMCID: PMC5979419 DOI: 10.3390/ijms19041207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 04/07/2018] [Accepted: 04/10/2018] [Indexed: 02/05/2023] Open
Abstract
The year 2016 marked the 20th anniversary of the death of Marcelle Grenson and the 50th anniversary of her first publication on yeast amino acid transport, the topic to which, as Professor at the Free University of Brussels (ULB), she devoted the major part of her scientific career. M. Grenson was the first scientist in Belgium to introduce and apply genetic analysis in yeast to dissect the molecular mechanisms that were underlying complex problems in biology. Today, M. Grenson is recognized for the pioneering character of her work on the diversity and regulation of amino acid transporters in yeast. The aim of this tribute is to review the major milestones of her forty years of scientific research that were conducted between 1950 and 1990.
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Affiliation(s)
- Bruno André
- Molecular Physiology of the Cell, Université Libre de Bruxelles (ULB), Biopark, 6041 Gosselies, Belgium.
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9
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Dal81 Regulates Expression of Arginine Metabolism Genes in Candida parapsilosis. mSphere 2018; 3:3/2/e00028-18. [PMID: 29564399 PMCID: PMC5853489 DOI: 10.1128/msphere.00028-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 02/08/2018] [Indexed: 01/26/2023] Open
Abstract
Fungi can use a wide variety of nitrogen sources. In the absence of preferred sources such as ammonium, glutamate, and glutamine, secondary sources, including most other amino acids, are used. Expression of the nitrogen utilization pathways is very strongly controlled at the transcriptional level. Here, we investigated the regulation of nitrogen utilization in the pathogenic yeast Candida parapsilosis. We found that the functions of many regulators are conserved with respect to Saccharomyces cerevisiae and other fungi. For example, the core GATA activators GAT1 and GLN3 have a conserved role in nitrogen catabolite repression (NCR). There is one ortholog of GZF3 and DAL80, which represses expression of genes in preferred nitrogen sources. The regulators PUT3 and UGA3 are required for metabolism of proline and γ-aminobutyric acid (GABA), respectively. However, the role of the Dal81 transcription factor is distinctly different. In S. cerevisiae, Dal81 is a positive regulator of acquisition of nitrogen from GABA, allantoin, urea, and leucine, and it is required for maximal induction of expression of the relevant pathway genes. In C. parapsilosis, induction of GABA genes is independent of Dal81, and deleting DAL81 has no effect on acquisition of nitrogen from GABA or allantoin. Instead, Dal81 represses arginine synthesis during growth under preferred nitrogen conditions. IMPORTANCE Utilization of nitrogen by fungi is controlled by nitrogen catabolite repression (NCR). Expression of many genes is switched off during growth on nonpreferred nitrogen sources. Gene expression is regulated through a combination of activation and repression. Nitrogen regulation has been studied best in the model yeast Saccharomyces cerevisiae. We found that although many nitrogen regulators have a conserved function in Saccharomyces species, some do not. The Dal81 transcriptional regulator has distinctly different functions in S. cerevisiae and C. parapsilosis. In the former, it regulates utilization of nitrogen from GABA and allantoin, whereas in the latter, it regulates expression of arginine synthesis genes. Our findings make an important contribution to our understanding of nitrogen regulation in a human-pathogenic fungus.
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Villers J, Savocco J, Szopinska A, Degand H, Nootens S, Morsomme P. Study of the Plasma Membrane Proteome Dynamics Reveals Novel Targets of the Nitrogen Regulation in Yeast. Mol Cell Proteomics 2017; 16:1652-1668. [PMID: 28679684 PMCID: PMC5587864 DOI: 10.1074/mcp.m116.064923] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 06/26/2017] [Indexed: 12/19/2022] Open
Abstract
Yeast cells, to be able to grow on a wide variety of nitrogen sources, regulate the set of nitrogen transporters present at their plasma membrane. Such regulation relies on both transcriptional and post-translational events. Although microarray studies have identified most nitrogen-sensitive genes, nitrogen-induced post-translational regulation has only been studied for very few proteins among which the general amino acid permease Gap1. Adding a preferred nitrogen source to proline-grown cells triggers Gap1 endocytosis and vacuolar degradation in an Rsp5-Bul1/2-dependent manner. Here, we used a proteomic approach to follow the dynamics of the plasma membrane proteome after addition of a preferred nitrogen source. We identified new targets of the nitrogen regulation and four transporters of poor nitrogen sources-Put4, Opt2, Dal5, and Ptr2-that rapidly decrease in abundance. Although the kinetics is different for each transporter, we found that three of them-Put4, Dal5, and Ptr2-are endocytosed, like Gap1, in an Rsp5-dependent manner and degraded in the vacuole. Finally, we showed that Gap1 stabilization at the plasma membrane, through deletion of Bul proteins, regulates the abundance of Put4, Dal5 and Ptr2.
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Affiliation(s)
- Jennifer Villers
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Jérôme Savocco
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Aleksandra Szopinska
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Hervé Degand
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Sylvain Nootens
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
| | - Pierre Morsomme
- From the ‡Université catholique de Louvain, Institut des Sciences de la Vie, Croix du Sud 4-5, B-1348 Louvain-la-Neuve
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11
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Mathieu C, Macêdo JP, Hürlimann D, Wirdnam C, Haindrich AC, Suter Grotemeyer M, González-Salgado A, Schmidt RS, Inbar E, Mäser P, Bütikofer P, Zilberstein D, Rentsch D. Arginine and Lysine Transporters Are Essential for Trypanosoma brucei. PLoS One 2017; 12:e0168775. [PMID: 28045943 PMCID: PMC5207785 DOI: 10.1371/journal.pone.0168775] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 12/06/2016] [Indexed: 12/14/2022] Open
Abstract
For Trypanosoma brucei arginine and lysine are essential amino acids and therefore have to be imported from the host. Heterologous expression in Saccharomyces cerevisiae mutants identified cationic amino acid transporters among members of the T. brucei AAAP (amino acid/auxin permease) family. TbAAT5-3 showed high affinity arginine uptake (Km 3.6 ± 0.4 μM) and high selectivity for L-arginine. L-arginine transport was reduced by a 10-times excess of L-arginine, homo-arginine, canavanine or arginine-β-naphthylamide, while lysine was inhibitory only at 100-times excess, and histidine or ornithine did not reduce arginine uptake rates significantly. TbAAT16-1 is a high affinity (Km 4.3 ± 0.5 μM) and highly selective L-lysine transporter and of the compounds tested, only L-lysine and thialysine were competing for L-lysine uptake. TbAAT5-3 and TbAAT16-1 are expressed in both procyclic and bloodstream form T. brucei and cMyc-tagged proteins indicate localization at the plasma membrane. RNAi-mediated down-regulation of TbAAT5 and TbAAT16 in bloodstream form trypanosomes resulted in growth arrest, demonstrating that TbAAT5-mediated arginine and TbAAT16-mediated lysine transport are essential for T. brucei. Growth of induced RNAi lines could partially be rescued by supplementing a surplus of arginine or lysine, respectively, while addition of both amino acids was less efficient. Single and double RNAi lines indicate that additional low affinity uptake systems for arginine and lysine are present in T. brucei.
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Affiliation(s)
| | - Juan P. Macêdo
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Daniel Hürlimann
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Corina Wirdnam
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | | | | | | | - Remo S. Schmidt
- Swiss Tropical and Public Health Institute and University of Basel, Basel, Switzerland
| | - Ehud Inbar
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Pascal Mäser
- Swiss Tropical and Public Health Institute and University of Basel, Basel, Switzerland
| | - Peter Bütikofer
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Dan Zilberstein
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Doris Rentsch
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
- * E-mail:
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12
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McCraw SL, Park DH, Jones R, Bentley MA, Rico A, Ratcliffe RG, Kruger NJ, Collmer A, Preston GM. GABA (γ-Aminobutyric Acid) Uptake Via the GABA Permease GabP Represses Virulence Gene Expression in Pseudomonas syringae pv. tomato DC3000. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2016; 29:938-949. [PMID: 28001093 DOI: 10.1094/mpmi-08-16-0172-r] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The nonprotein amino acid γ-aminobutyric acid (GABA) is the most abundant amino acid in the tomato (Solanum lycopersicum) leaf apoplast and is synthesized by Arabidopsis thaliana in response to infection by the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (hereafter called DC3000). High levels of exogenous GABA have previously been shown to repress the expression of the type III secretion system (T3SS) in DC3000, resulting in reduced elicitation of the hypersensitive response (HR) in the nonhost plant tobacco (Nicotiana tabacum). This study demonstrates that the GABA permease GabP provides the primary mechanism for GABA uptake by DC3000 and that the gabP deletion mutant ΔgabP is insensitive to GABA-mediated repression of T3SS expression. ΔgabP displayed an enhanced ability to elicit the HR in young tobacco leaves and in tobacco plants engineered to produce increased levels of GABA, which supports the hypothesis that GABA uptake via GabP acts to regulate T3SS expression in planta. The observation that P. syringae can be rendered insensitive to GABA through loss of gabP but that gabP is retained by this bacterium suggests that GabP is important for DC3000 in a natural setting, either for nutrition or as a mechanism for regulating gene expression. [Formula: see text] Copyright © 2016 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
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Affiliation(s)
- S L McCraw
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - D H Park
- 2 Department of Applied Biology, College of Agriculture and Life Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea
| | - R Jones
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - M A Bentley
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - A Rico
- 3 Departamento de Didáctica de la 9 Matemática y de las Ciencias Experimentales, Faculty of Education and Sport, University of the Basque Country UPV/EHU, Juan Ibañez de Sto. Domingo 1, 01006 Vitoria-Gasteiz, Spain; and
| | - R G Ratcliffe
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - N J Kruger
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - A Collmer
- 4 School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, U.S.A
| | - G M Preston
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
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13
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Isolation of baker's yeast mutants with proline accumulation that showed enhanced tolerance to baking-associated stresses. Int J Food Microbiol 2016; 238:233-240. [DOI: 10.1016/j.ijfoodmicro.2016.09.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 09/05/2016] [Accepted: 09/20/2016] [Indexed: 11/20/2022]
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14
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Fayyad-Kazan M, Feller A, Bodo E, Boeckstaens M, Marini AM, Dubois E, Georis I. Yeast nitrogen catabolite repression is sustained by signals distinct from glutamine and glutamate reservoirs. Mol Microbiol 2015; 99:360-79. [DOI: 10.1111/mmi.13236] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2015] [Indexed: 01/29/2023]
Affiliation(s)
- Mohammad Fayyad-Kazan
- Institut de Recherches Microbiologiques J.-M. Wiame; 1070 Brussels Belgium
- Laboratoire de Biologie du Transport Membranaire; Institut de Biologie et de Médecine Moléculaires; Université Libre de Bruxelles; 6041 Gosselies Belgium
| | - A. Feller
- Institut de Recherches Microbiologiques J.-M. Wiame; 1070 Brussels Belgium
- Laboratoire de Microbiologie; Institut de Biologie et de Médecine Moléculaires; Université Libre de Bruxelles; 6041 Gosselies Belgium
| | - E. Bodo
- Unité de Biotechnologie; 1070 Brussels Belgium
| | - M. Boeckstaens
- Laboratoire de Biologie du Transport Membranaire; Institut de Biologie et de Médecine Moléculaires; Université Libre de Bruxelles; 6041 Gosselies Belgium
| | - A. M. Marini
- Laboratoire de Biologie du Transport Membranaire; Institut de Biologie et de Médecine Moléculaires; Université Libre de Bruxelles; 6041 Gosselies Belgium
| | - E. Dubois
- Institut de Recherches Microbiologiques J.-M. Wiame; 1070 Brussels Belgium
- Laboratoire de Microbiologie; Institut de Biologie et de Médecine Moléculaires; Université Libre de Bruxelles; 6041 Gosselies Belgium
| | - I. Georis
- Institut de Recherches Microbiologiques J.-M. Wiame; 1070 Brussels Belgium
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15
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Pfannmüller A, Wagner D, Sieber C, Schönig B, Boeckstaens M, Marini AM, Tudzynski B. The General Amino Acid Permease FfGap1 of Fusarium fujikuroi Is Sorted to the Vacuole in a Nitrogen-Dependent, but Npr1 Kinase-Independent Manner. PLoS One 2015; 10:e0125487. [PMID: 25909858 PMCID: PMC4409335 DOI: 10.1371/journal.pone.0125487] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 03/14/2015] [Indexed: 12/18/2022] Open
Abstract
The rice pathogenic fungus Fusarium fujikuroi is well known for the production of a broad spectrum of secondary metabolites (SMs) such as gibberellic acids (GAs), mycotoxins and pigments. The biosynthesis of most of these SMs strictly depends on nitrogen availability and of the activity of permeases of nitrogen sources, e.g. the ammonium and amino acid permeases. One of the three ammonium permeases, MepB, was recently shown to act not only as a transporter but also as a nitrogen sensor affecting the production of nitrogen-repressed SMs. Here we describe the identification of a general amino acid permease, FfGap1, among the 99 putative amino acid permeases (AAPs) in the genome of F. fujikuroi. FfGap1 is able to fully restore growth of the yeast gap1∆ mutant on several amino acids including citrulline and tryptophane. In S. cerevisiae, Gap1 activity is regulated by shuttling between the plasma membrane (nitrogen limiting conditions) and the vacuole (nitrogen sufficiency), which we also show for FfGap1. In yeast, the Npr1 serine/threonine kinase stabilizes the Gap1 position at the plasma membrane. Here, we identified and characterized three NPR1-homologous genes, encoding the putative protein kinases FfNpr1-1, FfNpr1-2 and FfNpr1-3 with significant similarity to yeast Npr1. Complementation of the yeast npr1Δ mutant with each of the three F. fujikuroi NPR1 homologues, resulted in partial restoration of ammonium, arginine and proline uptake by FfNPR1-1 while none of the three kinases affect growth on different nitrogen sources and nitrogen-dependent sorting of FfGap1 in F. fujikuroi. However, exchange of the putative ubiquitin-target lysine 9 (K9A) and 15 (K15A) residues of FfGap1 resulted in extended localization to the plasma membrane and increased protein stability independently of nitrogen availability. These data suggest a similar regulation of FfGap1 by nitrogen-dependent ubiquitination, but differences regarding the role of Fusarium Npr1 homologues compared to yeast.
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Affiliation(s)
- Andreas Pfannmüller
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Dominik Wagner
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Christian Sieber
- Institute of Bioinformatics and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - Birgit Schönig
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Mélanie Boeckstaens
- Laboratoire de Biologie du Transport Membranaire, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, Gosselies, Belgium
| | - Anna Maria Marini
- Laboratoire de Biologie du Transport Membranaire, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, Gosselies, Belgium
| | - Bettina Tudzynski
- Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Münster, Germany
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16
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Trypanosoma brucei eflornithine transporter AAT6 is a low-affinity low-selective transporter for neutral amino acids. Biochem J 2014; 463:9-18. [PMID: 24988048 DOI: 10.1042/bj20140719] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Amino acid transporters are crucial for parasite survival since the cellular metabolism of parasitic protozoa depends on the up-take of exogenous amino acids. Amino acid transporters are also of high pharmacological relevance because they may mediate uptake of toxic amino acid analogues. In the present study we show that the eflornithine transporter AAT6 from Trypanosoma brucei (TbAAT6) mediates growth on neutral amino acids when expressed in Saccharomyces cerevisiae mutants. The transport was electrogenic and further analysed in Xenopus laevis oocytes. Neutral amino acids, proline analogues, eflornithine and acivicin induced inward currents. For proline, glycine and tryptophan the apparent affinities and maximal transport rates increased with more negative membrane potentials. Proline-induced currents were dependent on pH, but not on sodium. Although proline represents the primary energy source of T. brucei in the tsetse fly, down-regulation of TbAAT6-expression by RNAi showed that in culture TbAAT6 is not essential for growth of procyclic form trypanosomes in the presence of glucose or proline as energy source. TbAAT6-RNAi lines of both bloodstream and procyclic form trypanosomes showed reduced susceptibility to eflornithine, whereas the sensitivity to acivicin remained unchanged, indicating that acivicin enters the cell by more than one transporter.
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17
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Cao J, Singh NK, Locy RD. Characterization of the recombinant succinic semi-aldehyde dehydrogenase from Saccharomyces cerevisiae. Yeast 2014; 31:411-20. [PMID: 25092794 DOI: 10.1002/yea.3035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 07/22/2014] [Accepted: 07/27/2014] [Indexed: 11/12/2022] Open
Abstract
The yeast succinic semi-aldehyde dehydrogenase gene (SSADH; EC 1.2.1.16) was cloned and overexpressed in Escherichia coli. Based on SDS-PAGE, the molecular mass of the subunit was around 54 kDa, and the purified recombinant enzyme had a tetrameric molecular mass of ca. 200 kDa. The specific activity of the recombinant enzyme was 1.90 µM NADH formed/min/mg, and showed maximal activity at pH 8.4. The recombinant protein was highly specific for succinate semi-aldehyde (Km = 15.48 ± 0.14 µM) and could use both NAD(+) and NADP(+) as co-factors, with Km values of 579.06 ± 30.1 µM and 1.017 ± 0.46 mM, respectively. Initial velocity studies showed that NADH was a competitive inhibitor with respect to NAD(+) (Ki = 129.5 µM) but a non-competitive inhibitor with respect to succinate semi-aldehyde. Adenine nucleotides of AMP, ADP and ATP inhibited yeast SSADH activity with Ki = 1.13-10.2 mM, and showed competitive inhibition with respect to NAD(+) and mixed-competitive, non-competitive and non-competitive inhibition, respectively, with respect to succinate semi-aldehyde. The kinetic data suggest a 'ping-pong' mechanism.
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Affiliation(s)
- Juxiang Cao
- Department of Biological Sciences, Auburn University, AL, USA; Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
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18
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Differential transcribed yeast genes involved in flavour formation and its associated amino acid metabolism during brewery fermentation. Eur Food Res Technol 2014. [DOI: 10.1007/s00217-014-2236-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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L-Phenylalanine Transport in Saccharomyces cerevisiae: Participation of GAP1, BAP2, and AGP1. JOURNAL OF AMINO ACIDS 2014; 2014:283962. [PMID: 24701347 PMCID: PMC3950631 DOI: 10.1155/2014/283962] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 12/01/2013] [Accepted: 12/30/2013] [Indexed: 01/13/2023]
Abstract
We focused on the participation of GAP1, BAP2, and AGP1 in L-phenylalanine transport in yeast. In order to study the physiological functions of GAP1, BAP2, and AGP1 in L-phenylalanine transport, we examined the kinetics, substrate specificity, and regulation of these systems, employing isogenic haploid strains with the respective genes disrupted individually and in combination. During the characterization of phenylalanine transport, we noted important regulatory phenomena associated with these systems. Our results show that Agp1p is the major transporter of the phenylalanine in a gap1 strain growing in synthetic media with leucine present as an inducer. In a wild type strain grown in the presence of leucine, when ammonium ion was the nitrogen source, Bap2p is the principal phenylalanine carrier.
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20
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The γ-aminobutyrate permease GabP serves as the third proline transporter of Bacillus subtilis. J Bacteriol 2013; 196:515-26. [PMID: 24142252 DOI: 10.1128/jb.01128-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PutP and OpuE serve as proline transporters when this imino acid is used by Bacillus subtilis as a nutrient or as an osmostress protectant, respectively. The simultaneous inactivation of the PutP and OpuE systems still allows the utilization of proline as a nutrient. This growth phenotype pointed to the presence of a third proline transport system in B. subtilis. We took advantage of the sensitivity of a putP opuE double mutant to the toxic proline analog 3,4-dehydro-dl-proline (DHP) to identify this additional proline uptake system. DHP-resistant mutants were selected and found to be defective in the use of proline as a nutrient. Whole-genome resequencing of one of these strains provided the lead that the inactivation of the γ-aminobutyrate (GABA) transporter GabP was responsible for these phenotypes. DNA sequencing of the gabP gene in 14 additionally analyzed DHP-resistant strains confirmed this finding. Consistently, each of the DHP-resistant mutants was defective not only in the use of proline as a nutrient but also in the use of GABA as a nitrogen source. The same phenotype resulted from the targeted deletion of the gabP gene in a putP opuE mutant strain. Hence, the GabP carrier not only serves as an uptake system for GABA but also functions as the third proline transporter of B. subtilis. Uptake studies with radiolabeled GABA and proline confirmed this conclusion and provided information on the kinetic parameters of the GabP carrier for both of these substrates.
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21
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Δ(1)-pyrroline-5-carboxylate/glutamate biogenesis is required for fungal virulence and sporulation. PLoS One 2013; 8:e73483. [PMID: 24039956 PMCID: PMC3767830 DOI: 10.1371/journal.pone.0073483] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 07/22/2013] [Indexed: 11/19/2022] Open
Abstract
Proline dehydrogenase (Prodh) and Δ1-pyrroline-5-carboxylate dehydrogenase (P5Cdh) are two key enzymes in the cellular biogenesis of glutamate. Recombinant Prodh and P5Cdh proteins of the chestnut blight fungus Cryphonectria parasitica were investigated and showed activity in in vitro assays. Additionally, the C. parasitica Prodh and P5Cdh genes were able to complement the Saccharomyces cerevisiae put1 and put2 null mutants, respectively, to allow these proline auxotrophic yeast mutants to grow on media with proline as the sole source of nitrogen. Deletion of the Prodh gene in C. parasitica resulted in hypovirulence and a lower level of sporulation, whereas deletion of P5Cdh resulted in hypovirulence though no effect on sporulation; both Δprodh and Δp5cdh mutants were unable to grow on minimal medium with proline as the sole nitrogen source. In a wild-type strain, the intracellular level of proline and the activity of Prodh and P5Cdh increased after supplementation of exogenous proline, though the intracellular Δ1-pyrroline-5-carboxylate (P5C) content remained unchanged. Prodh and P5Cdh were both transcriptionally down-regulated in cells infected with hypovirus. The disruption of other genes with products involved in the conversion of arginine to ornithine, ornithine and glutamate to P5C, and P5C to proline in the cytosol did not appear to affect virulence; however, asexual sporulation was reduced in the Δpro1 and Δpro2 mutants. Taken together, our results showed that Prodh, P5Cdh and related mitochondrial functions are essential for virulence and that proline/glutamate pathway components may represent down-stream targets of hypovirus regulation in C. parasitica.
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22
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Pallotta ML. L-Proline uptake in Saccharomyces cerevisiae mitochondria can contribute to bioenergetics during nutrient stress as alternative mitochondrial fuel. World J Microbiol Biotechnol 2013; 30:19-31. [PMID: 23824663 DOI: 10.1007/s11274-013-1415-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 06/23/2013] [Indexed: 11/28/2022]
Abstract
L-Proline (pyrrolidine-2-carboxylic acid) is a distinctive metabolite both biochemically and biotechnologically and is currently recognized to have a cardinal role in gene expression and cellular signaling pathways in stress response. Proline-fueled mitochondrial metabolism involves the oxidative conversion of L-Proline to L-Glutamate in two enzymatic steps by means of Put1p and Put2p that help Saccharomyces cerevisiae to respond to changes in the nutritional environment by initiating the breakdown of L-Proline as a source for nitrogen, carbon, and energy. Compartmentalization of L-Proline catabolic pathway implies that extensive L-Proline transport must take place between the cytosol where its biogenesis via Pro1p, Pro2p, Pro3p occurs and mitochondria. L-Proline uptake in S. cerevisiae purified and active mitochondria was investigated by swelling experiments, oxygen uptake and fluorimetric measurement of a membrane potential generation (ΔΨ). Our results strongly suggest that L-Proline uptake occurs via a carried-mediated process as demonstrated by saturation kinetics and experiments with N-ethylmaleimide, a pharmacological compound that is a cysteine-modifying reagent in hydrophobic protein domains and that inhibited mitochondrial transport. Plasticity of S. cerevisiae cell biochemistry according to background fluctuations is an important factor of adaptation to stress. Thus L-Proline → Glutamate route feeds Krebs cycle providing energy and anaplerotic carbon for yeast survival.
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Affiliation(s)
- Maria Luigia Pallotta
- Department of Medicine and Health Sciences, University of Molise, 86100, Campobasso, Italy,
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23
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Cao J, Barbosa JM, Singh NK, Locy RD. GABA shunt mediates thermotolerance inSaccharomyces cerevisiaeby reducing reactive oxygen production. Yeast 2013; 30:129-44. [DOI: 10.1002/yea.2948] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 02/05/2013] [Accepted: 02/08/2013] [Indexed: 11/05/2022] Open
Affiliation(s)
| | | | | | - Robert D. Locy
- Department of Biological Sciences; Auburn University; AL; USA
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24
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A versatile proline/alanine transporter in the unicellular pathogen Leishmania donovani regulates amino acid homoeostasis and osmotic stress responses. Biochem J 2013; 449:555-66. [PMID: 22994895 DOI: 10.1042/bj20121262] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Unlike all other organisms, parasitic protozoa of the family Trypanosomatidae maintain a large cellular pool of proline that, together with the alanine pool, serve as alternative carbon sources as well as reservoirs of organic osmolytes. These reflect adaptation to their insect vectors whose haemolymphs are exceptionally rich in the two amino acids. In the present study we identify and characterize a new neutral amino acid transporter, LdAAP24, that translocates proline and alanine across the Leishmania donovani plasma membrane. This transporter fulfils multiple functions: it is the sole supplier for the intracellular pool of proline and contributes to the alanine pool; it is essential for cell volume regulation after osmotic stress; and it regulates the transport and homoeostasis of glutamate and arginine, none of which are its substrates. Notably, we provide evidence that proline and alanine exhibit different roles in the parasitic response to hypotonic shock; alanine affects swelling, whereas proline influences the rate of volume recovery. On the basis of our data we suggest that LdAAP24 plays a key role in parasite adaptation to its varying environments in host and vector, a phenomenon essential for successful parasitism.
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25
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Sequential use of nitrogen compounds by Saccharomyces cerevisiae during wine fermentation: a model based on kinetic and regulation characteristics of nitrogen permeases. Appl Environ Microbiol 2012; 78:8102-11. [PMID: 22983966 DOI: 10.1128/aem.02294-12] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The efficiency of nitrogen use is a key determinant of the completion of alcoholic fermentation. We analyzed the kinetics of consumption of 18 nitrogen compounds by 14 Saccharomyces cerevisiae strains of various origins in a synthetic medium that mimicked a grape must. The kinetic profiles of total nitrogen consumption were diverse, but the order of nitrogen source consumption was similar for all strains. The nitrogen compounds could be classified into three groups, according to their order of use: prematurely consumed (Lys), early consumed (Asp, Thr, Glu, Leu, His, Met, Ile, Ser, Gln, and Phe), and late consumed (ammonium, Val, Arg, Ala, Trp, and Tyr). The initial concentrations of these compounds did not alter the order in which they were consumed, except for arginine and ammonium. Early consumed amino acids are transported by specific permeases under Ssy1p-Ptr3p-Ssy5 (SPS)-mediated control that are expressed at the beginning of consumption. Most nitrogen compounds consumed late are transported by permeases under nitrogen catabolite repression (NCR), and others (Val, Trp, and Tyr) are transported by SPS-regulated low-affinity permeases. Therefore, the kinetic characteristics of transporters, as well as SPS and NCR, are likely key factors controlling the temporal sequence of consumption of nitrogen compounds and constitute a system highly conserved in S. cerevisiae species. This work sheds new light on the mechanistic basis of the sequential use of different nitrogen compounds in complex environments.
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26
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Regulation of amino acid, nucleotide, and phosphate metabolism in Saccharomyces cerevisiae. Genetics 2012; 190:885-929. [PMID: 22419079 DOI: 10.1534/genetics.111.133306] [Citation(s) in RCA: 338] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Ever since the beginning of biochemical analysis, yeast has been a pioneering model for studying the regulation of eukaryotic metabolism. During the last three decades, the combination of powerful yeast genetics and genome-wide approaches has led to a more integrated view of metabolic regulation. Multiple layers of regulation, from suprapathway control to individual gene responses, have been discovered. Constitutive and dedicated systems that are critical in sensing of the intra- and extracellular environment have been identified, and there is a growing awareness of their involvement in the highly regulated intracellular compartmentalization of proteins and metabolites. This review focuses on recent developments in the field of amino acid, nucleotide, and phosphate metabolism and provides illustrative examples of how yeast cells combine a variety of mechanisms to achieve coordinated regulation of multiple metabolic pathways. Importantly, common schemes have emerged, which reveal mechanisms conserved among various pathways, such as those involved in metabolite sensing and transcriptional regulation by noncoding RNAs or by metabolic intermediates. Thanks to the remarkable sophistication offered by the yeast experimental system, a picture of the intimate connections between the metabolomic and the transcriptome is becoming clear.
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27
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Yamada N, Sakakibara S, Tsutsumi K, Waditee R, Tanaka Y, Takabe T. Expression and substrate specificity of betaine/proline transporters suggest a novel choline transport mechanism in sugar beet. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:1609-16. [PMID: 21511362 DOI: 10.1016/j.jplph.2011.03.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2010] [Revised: 03/15/2011] [Accepted: 03/22/2011] [Indexed: 05/03/2023]
Abstract
Proline transporters (ProTs) originally described as highly selective transporters for proline, have been shown to also transport glycinebetaine (betaine). Here we examined and compared the transport properties of Bet/ProTs from betaine accumulating (sugar beet, Amaranthus, and Atriplex,) and non-accumulating (Arabidopsis) plants. Using a yeast mutant deficient for uptake of proline and betaine, it was shown that all these transporters exhibited higher affinity for betaine than proline. The uptake of betaine and proline was pH-dependent and inhibited by the proton uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). We also investigated choline transport by using a choline transport-deficient yeast mutant. Results revealed that these transporters exhibited a higher affinity for choline uptake rather than betaine. Uptake of choline by sugar beet BvBet/ProT1 was independent of the proton gradient and the inhibition by CCCP was reduced compared with that for uptake of betaine, suggesting different proton binding properties between the transport of choline and betaine. Additionally, in situ hybridization experiments revealed the localization of sugar beet BvBet/ProT1 in phloem and xylem parenchyma cells.
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Affiliation(s)
- Nana Yamada
- Graduate School of Environmental and Human Sciences, Meijo University, Nagoya 468-8502, Japan
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28
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Michaeli S, Fait A, Lagor K, Nunes-Nesi A, Grillich N, Yellin A, Bar D, Khan M, Fernie AR, Turano FJ, Fromm H. A mitochondrial GABA permease connects the GABA shunt and the TCA cycle, and is essential for normal carbon metabolism. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 67:485-98. [PMID: 21501262 DOI: 10.1111/j.1365-313x.2011.04612.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In plants, γ-aminobutyric acid (GABA) accumulates in the cytosol in response to a variety of stresses. GABA is transported into mitochondria, where it is catabolized into TCA cycle or other intermediates. Although there is circumstantial evidence for mitochondrial GABA transporters in eukaryotes, none have yet been identified. Described here is an Arabidopsis protein similar in sequence and topology to unicellular GABA transporters. The expression of this protein complements a GABA-transport-deficient yeast mutant. Thus the protein was termed AtGABP to indicate GABA-permease activity. In vivo localization of GABP fused to GFP and immunobloting of subcellular fractions demonstrate its mitochondrial localization. Direct [(3) H]GABA uptake measurements into isolated mitochondria revealed impaired uptake into mitochondria of a gabp mutant compared with wild-type (WT) mitochondria, implicating AtGABP as a major mitochondrial GABA carrier. Measurements of CO(2) release, derived from radiolabeled substrates in whole seedlings and in isolated mitochondria, demonstrate impaired GABA-derived input into the TCA cycle, and a compensatory increase in TCA cycle activity in gabp mutants. Finally, growth abnormalities of gabp mutants under limited carbon availability on artificial media, and in soil under low light intensity, combined with their metabolite profiles, suggest an important role for AtGABP in primary carbon metabolism and plant growth. Thus, AtGABP-mediated transport of GABA from the cytosol into mitochondria is important to ensure proper GABA-mediated respiration and carbon metabolism. This function is particularly essential for plant growth under conditions of limited carbon.
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Affiliation(s)
- Simon Michaeli
- Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
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29
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Yamada N, Cha-Um S, Kageyama H, Promden W, Tanaka Y, Kirdmanee C, Takabe T. Isolation and characterization of proline/betaine transporter gene from oil palm. TREE PHYSIOLOGY 2011; 31:462-468. [PMID: 21474553 DOI: 10.1093/treephys/tpr017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Oil production from oil palm is adversely affected by drought and salt. Under drought and salt stress, proline content increases in oil palm; the mechanism for this is unknown. Here, an 8319-nucleotide sequence including cDNA, genomic DNA and the promoter region of proline transporter gene from oil palm Elaeis guineensis was determined. The transporter gene exhibited high similarity to Bet/ProT genes from several plants, but the highest homology was found with rice ProT1. The exon-intron structure of genomic DNA was unique, and numerous stress-response cis-elements were found in the promoter region. Expression of cDNA EgProT1 in Escherichia coli mutant exhibited uptake activities for glycinebetaine and choline as well as proline. Under salt-stressed conditions, exogenously applied glycinebetaine was taken up into the root more rapidly than the control. These data indicate that oil palm has a unique Pro/T1 gene. Nucleotide sequence data for the cDNA and genomic DNA of proline transporter gene from Elaeis guineensis are available in the DDJB database under accession numbers AB597035 and AB597036, respectively.
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MESH Headings
- Amino Acid Transport Systems, Neutral/drug effects
- Amino Acid Transport Systems, Neutral/genetics
- Amino Acid Transport Systems, Neutral/metabolism
- Arecaceae/drug effects
- Arecaceae/genetics
- Arecaceae/metabolism
- Base Sequence
- Betaine/analysis
- Betaine/metabolism
- Biological Transport
- Carrier Proteins/drug effects
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Choline/metabolism
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Plant/chemistry
- DNA, Plant/genetics
- GABA Plasma Membrane Transport Proteins
- Green Fluorescent Proteins
- Molecular Sequence Data
- Phylogeny
- Proline/analysis
- Proline/metabolism
- Promoter Regions, Genetic/genetics
- RNA, Messenger/genetics
- RNA, Plant/genetics
- Seeds/genetics
- Seeds/metabolism
- Sequence Analysis, DNA
- Sodium Chloride/pharmacology
- Stress, Physiological
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Affiliation(s)
- Nana Yamada
- Graduate School of Environmental and Human Sciences, Meijo University, Nagoya 468-8502, Japan
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30
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Lehmann S, Gumy C, Blatter E, Boeffel S, Fricke W, Rentsch D. In planta function of compatible solute transporters of the AtProT family. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:787-96. [PMID: 20959625 PMCID: PMC3003823 DOI: 10.1093/jxb/erq320] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The three proline transporters of Arabidopsis thaliana (AtProTs) transport the compatible solutes proline and glycine betaine and the stress-induced compound γ-aminobutyric acid when expressed in heterologous systems. The aim of the present study was to show transport and physiological relevance of these three AtProTs in planta. Using single, double, and triple knockout mutants and AtProT-overexpressing lines, proline content, growth on proline, transport of radiolabelled betaine, and expression of AtProT genes and enzymes of proline metabolism were analysed. AtProT2 was shown to facilitate uptake of L- and D-proline as well as [(14)C]glycine betaine in planta, indicating a role in the import of compatible solutes into the root. Toxic concentrations of L- and D-proline resulted in a drastic growth retardation of AtProT-overexpressing plants, demonstrating the need for a precise regulation of proline uptake and/or distribution. Furthermore evidence is provided that AtProT genes are highly expressed in tissues with elevated proline content--that is, pollen and leaf epidermis.
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Affiliation(s)
- Silke Lehmann
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Christophe Gumy
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Eva Blatter
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Silke Boeffel
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Wieland Fricke
- School of Biology and Environmental Science, UCD Science Centre West, University College Dublin, Belfield, Dublin 4, Ireland
| | - Doris Rentsch
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
- To whom correspondence should be addressed. E-mail:
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31
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Cooper SJ, Finney GL, Brown SL, Nelson SK, Hesselberth J, MacCoss MJ, Fields S. High-throughput profiling of amino acids in strains of the Saccharomyces cerevisiae deletion collection. Genome Res 2010; 20:1288-96. [PMID: 20610602 DOI: 10.1101/gr.105825.110] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The measurement of small molecule metabolites on a large scale offers the opportunity for a more complete understanding of cellular metabolism. We developed a high-throughput method to quantify primary amine-containing metabolites in the yeast Saccharomyces cerevisiae by the use of capillary electrophoresis in combination with fluorescent derivatization of cell extracts. We measured amino acid levels in the yeast deletion collection, a set of approximately 5000 strains each lacking a single gene, and developed a computational pipeline for data analysis. Amino acid peak assignments were validated by mass spectrometry, and the overall approach was validated by the result that expected pathway intermediates accumulate in mutants of the arginine biosynthetic pathway. Global analysis of the deletion collection was carried out using clustering methods. We grouped strains based on their metabolite profiles, revealing clusters of mutants enriched for genes encoding mitochondrial proteins, urea cycle enzymes, and vacuolar ATPase functions. One of the most striking profiles, common among several strains lacking ribosomal protein genes, accumulated lysine and a lysine-related metabolite. Mutations in the homologous ribosomal protein genes in the human result in Diamond-Blackfan anemia, demonstrating that metabolite data may have potential value in understanding disease pathology. This approach establishes metabolite profiling as capable of characterizing genes in a large collection of genetic variants.
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Affiliation(s)
- Sara J Cooper
- Department of Genome Sciences, University of Washington, Seattle, Washington 98195, USA
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32
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Fujiwara T, Mitsuya S, Miyake H, Hattori T, Takabe T. Characterization of a novel glycinebetaine/proline transporter gene expressed in the mestome sheath and lateral root cap cells in barley. PLANTA 2010; 232:133-43. [PMID: 20376676 DOI: 10.1007/s00425-010-1155-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 03/17/2010] [Indexed: 05/09/2023]
Abstract
The accumulation of glycinebetaine (GB) is one of the adaptive strategies to adverse salt stress conditions. Although it has been demonstrated that barley plants accumulate GB in response to salt stress and various studies focused on GB synthesis were performed, its transport mechanism is still unclear. In this study, we identified a novel gene, HvProT2, encoding Hordeum vulgare GB/proline transporter from barley plants. Heterologous expression in yeast (Saccharomyces cerevisiae) mutant demonstrated that the affinity of HvProT2 was highest for GB, intermediate for proline and lowest for gamma-aminobutyric acid. Transient expression of fusions of HvProT2 and green fluorescent protein in onion epidermal cells revealed that HvProT2 is localized at the plasma membrane. Relative quantification of mRNA level of HvProT2 using semi-quantitative reverse transcription-polymerase chain reaction analysis showed that HvProT2 is constitutively expressed in both leaves and roots, and the expression level was higher in old leaves than young leaves and roots. Moreover, we found that HvProT2 was expressed in the mestome sheath and lateral root cap cells. We discussed the possible involvement of HvProT2 for salt stress tolerance.
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Affiliation(s)
- Takashi Fujiwara
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan
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33
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Poole K, E Walker M, Warren T, Gardner J, McBryde C, de Barros Lopes M, Jiranek V. Proline transport and stress tolerance of ammonia-insensitive mutants of the PUT4-encoded proline-specific permease in yeast. J GEN APPL MICROBIOL 2010; 55:427-39. [PMID: 20118607 DOI: 10.2323/jgam.55.427] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The imino amino acid, proline, has roles in both cellular nutrition and response to stress. Proline uptake in Saccharomyces cerevisiae is largely mediated by a high affinity, specific permease, Put4p, and a low affinity general amino acid permease, Gap1p. Both are subject to nitrogen catabolite repression (NCR) and nitrogen catabolite inactivation (NCI). In order for proline to be fully exploited, its transport must be derepressed, as occurs upon depletion of preferred nitrogen sources, and molecular oxygen must be present to allow the first step of catabolism via proline oxidase. This study focuses on the isolation of variants of Put4p, which are insensitive to repression by a preferred nitrogen source (ammonia) and their subsequent effect on proline transport and stress tolerance. Specific amino acid residues in the carboxy-terminal region of Put4p were targeted by site-directed mutagenesis. Substitution at Serine(605), a potential phosphorylation target, led to the amelioration of ammonia-induced down-regulation of Put4p. When combined with a promoter mutation (-160), the S(605)A mutation resulted in increased proline uptake and accumulation. This increase in proline accumulation was associated with increased cell viability in conditions of high temperature and osmotic stress raising possible benefits in industrial fermentation applications.
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Affiliation(s)
- Kate Poole
- School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, Australia
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34
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Lehmann S, Funck D, Szabados L, Rentsch D. Proline metabolism and transport in plant development. Amino Acids 2010; 39:949-62. [DOI: 10.1007/s00726-010-0525-3] [Citation(s) in RCA: 225] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 02/10/2010] [Indexed: 01/21/2023]
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35
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Yamada N, Promden W, Yamane K, Tamagake H, Hibino T, Tanaka Y, Takabe T. Preferential accumulation of betaine uncoupled to choline monooxygenase in young leaves of sugar beet--importance of long-distance translocation of betaine under normal and salt-stressed conditions. JOURNAL OF PLANT PHYSIOLOGY 2009; 166:2058-70. [PMID: 19647889 DOI: 10.1016/j.jplph.2009.06.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 06/28/2009] [Accepted: 06/28/2009] [Indexed: 05/03/2023]
Abstract
It has been reported that glycinebetaine (betaine) is synthesized in response to abiotic stresses via a two-step oxidation of choline in which choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH) are involved. Here we show that significant amounts of betaine, > 20 micromol/gFW, accumulated in young leaves of Beta vulgaris even under normal growth conditions, whereas levels in old leaves, cotyledons, hypocotyls, and roots were low. Under the same conditions, CMO accumulates exclusively in old leaves and is difficult to be detected in young leaves. By contrast, the levels of BADH were high in all tissues. Exogenously supplied choline was converted into betaine in old leaves, but levels were significantly lower in young leaves under the same conditions. When d(11)-betaine was applied exogenously to old leaves, it was translocated preferentially into young leaves and roots. In response to salt stress, betaine levels increased in all tissues, but most significantly increased in young leaves. The levels of CMO increased in various tissues, but were low in young leaves. A betaine transporter gene was isolated. Its expression was more strongly induced in old leaves than in young leaves. Based on these data, we discussed the role of CMO and betaine transporter under stress and non-stress conditions.
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Affiliation(s)
- Nana Yamada
- Graduate School of Environmental and Human Sciences, Meijo University, Nagoya 468-8502, Japan
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36
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New insights into {gamma}-aminobutyric acid catabolism: Evidence for {gamma}-hydroxybutyric acid and polyhydroxybutyrate synthesis in Saccharomyces cerevisiae. Appl Environ Microbiol 2009; 75:4231-9. [PMID: 19411412 DOI: 10.1128/aem.00051-09] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gamma-aminobutyrate (GABA) shunt, an alternative route for the conversion of alpha-ketoglutarate to succinate, involves the glutamate decarboxylase Gad1p, the GABA transaminase Uga1p and the succinate semialdehyde dehydrogenase Uga2p. This pathway has been extensively described in plants and animals, but its function in yeast remains unclear. We show that the flux through Gad1p is insignificant during fermentation in rich sugar-containing medium, excluding a role for this pathway in redox homeostasis under anaerobic conditions or sugar stress. However, we found that up to 4 g of exogenous GABA/liter was efficiently consumed by yeast. We studied the fate of this consumed GABA. Most was converted into succinate, with a reaction yield of 0.7 mol/mol. We also showed that a large proportion of GABA was stored within cells, indicating a possible role for this molecule in stress tolerance mechanisms or nitrogen storage. Furthermore, based on enzymatic and metabolic evidence, we identified an alternative route for GABA catabolism, involving the reduction of succinate-semialdehyde into gamma-hydroxybutyric acid and the polymerization of gamma-hydroxybutyric acid to form poly-(3-hydroxybutyric acid-co-4-hydroxybutyric acid). This study provides the first demonstration of a native route for the formation of this polymer in yeast. Our findings shed new light on the GABA pathway and open up new opportunities for industrial applications.
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37
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Barnett JA. A history of research on yeasts 13. Active transport and the uptake of various metabolites. Yeast 2008; 25:689-731. [PMID: 18951365 DOI: 10.1002/yea.1630] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- James A Barnett
- School of Biological Sciences, University of East Anglia, Norwich, UK.
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38
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Lee YH, Foster J, Chen J, Voll LM, Weber APM, Tegeder M. AAP1 transports uncharged amino acids into roots of Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 50:305-19. [PMID: 17419840 DOI: 10.1111/j.1365-313x.2007.03045.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Amino acids are available to plants in some soils in significant amounts, and plants frequently make use of these nitrogen sources. The goal of this study was to identify transporters involved in the uptake of amino acids into root cells. Based on the fact that high concentrations of amino acids inhibit plant growth, we hypothesized that mutants tolerating toxic levels of amino acids might be deficient in the uptake of amino acids from the environment. To test this hypothesis, we employed a forward genetic screen for Arabidopsis thaliana mutants tolerating toxic concentrations of amino acids in the media. We identified an Arabidopsis mutant that is deficient in the amino acid permease 1 (AAP1, At1g58360) and resistant to 10 mm phenylalanine and a range of other amino acids. The transporter was localized to the plasma membrane of root epidermal cells, root hairs, and throughout the root tip of Arabidopsis. Feeding experiments with [(14)C]-labeled neutral, acidic and basic amino acids showed significantly reduced uptake of amino acids in the mutant, underscoring that increased tolerance of aap1 to high levels of amino acids is coupled with reduced uptake by the root. The growth and uptake studies identified glutamate, histidine and neutral amino acids, including phenylalanine, as physiological substrates for AAP1, whereas aspartate, lysine and arginine are not. We also demonstrate that AAP1 imports amino acids into root cells when these are supplied at ecologically relevant concentrations. Together, our data indicate an important role of AAP1 for efficient use of nitrogen sources present in the rhizosphere.
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Affiliation(s)
- Yong-Hwa Lee
- School of Biological Sciences, Center for Integrated Biotechnology, Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA
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39
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HONJOH KI, MACHIDA T, NISHI K, MATSUURA K, SOLI KW, SAKAI T, ISHIKAWA H, MATSUMOTO K, MIYAMOTO T, IIO M. Improvement of Freezing and Oxidative Stress Tolerance in Saccharomyces cerevisiae by Taurine. FOOD SCIENCE AND TECHNOLOGY RESEARCH 2007. [DOI: 10.3136/fstr.13.145] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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40
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Feller A, Boeckstaens M, Marini AM, Dubois E. Transduction of the nitrogen signal activating Gln3-mediated transcription is independent of Npr1 kinase and Rsp5-Bul1/2 ubiquitin ligase in Saccharomyces cerevisiae. J Biol Chem 2006; 281:28546-54. [PMID: 16864574 DOI: 10.1074/jbc.m605551200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitrogen Catabolite Repression (NCR) allows the adaptation of yeast cells to the quality of nitrogen supply by inhibiting the transcription of genes encoding proteins involved in transport and degradation of nonpreferred nitrogen sources. In cells using ammonium or glutamine, the GATA transcription factor Gln3 is sequestered in the cytoplasm by Ure2 whereas it enters the nucleus after a shift to a nonpreferred nitrogen source like proline or upon addition of rapamycin, the TOR complex inhibitor. Recently, the Npr1 kinase and the Rsp5, Bul1/2 ubiquitin ligase complex were reported to have antagonistic roles in the nuclear import and Gln3-mediated activation. The Npr1 kinase controls the activity of various permeases including transporters for nitrogen sources that stimulate NCR such as the Mep ammonium transport systems. Combining data from growth tests, Northern blot analysis and Gln3 immunolocalization, we show that the Npr1 kinase is not a direct negative regulator of Gln3-dependent transcription. The derepression of Gln3-activated genes in ammonium-grown npr1 cells results from the reduced uptake of the nitrogen-repressing compound because NCR could be restored in npr1 cells by repairing ammonium-uptake defects through different means. Finally, we show that the impairment of the ubiquitin ligase complex does not prevent induction of NCR genes under nonpreferred nitrogen conditions. The apparent Rsp5-, Bul1/2-dependent Gln3 activation keeps to the cellular status, as it is only observed in cells having left the balanced phase of exponential growth.
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Affiliation(s)
- André Feller
- Institut de Recherches Microbiologiques J-M Wiame, Laboratoire de Microbiologie, Université Libre de Bruxelles, 1070 Brussels, Belgium
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41
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Shaked-Mishan P, Suter-Grotemeyer M, Yoel-Almagor T, Holland N, Zilberstein D, Rentsch D. A novel high-affinity arginine transporter from the human parasitic protozoan Leishmania donovani. Mol Microbiol 2006; 60:30-8. [PMID: 16556218 DOI: 10.1111/j.1365-2958.2006.05060.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We describe the first functional and molecular characterization of an amino acid permease (LdAAP3) from the human parasitic protozoan Leishmania donovani, the causative agent of visceral leishmaniasis in humans. This permease contains 480 amino acids with 11 predicted trans-membrane domains. Expressing LdAAP3 in Saccharomyces cerevisiae mutants revealed that LdAAP3 codes for a high-affinity arginine transporter (Km 1.9 microM). LdAAP3 is highly specific for arginine as its transport was not inhibited by other amino acids or arginine-related compounds. Using green fluorescence protein (GFP) fused to the N-terminus of LdAAP3, this transporter was localized to the surface membrane of promastigotes. The GFP-LdAAP3 chimera mediated a threefold increase in arginine transport in promastigotes, indicating that it is active and confirmed that LdAAP3 codes for an arginine transporter in parasite cells as well. LdAAP3 is novel as it shares a high level of homology with amino acid permeases from other trypanosomatidae but almost none with permeases from other phyla. The results of this work suggest that LdAAP3 might play a role in host-parasite interaction.
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Affiliation(s)
- Pninit Shaked-Mishan
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
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42
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Meyer A, Eskandari S, Grallath S, Rentsch D. AtGAT1, a high affinity transporter for gamma-aminobutyric acid in Arabidopsis thaliana. J Biol Chem 2006; 281:7197-204. [PMID: 16407306 PMCID: PMC3009663 DOI: 10.1074/jbc.m510766200] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Functional characterization of Arabidopsis thaliana GAT1 in heterologous expression systems, i.e. Saccharomyces cerevisiae and Xenopus laevis oocytes, revealed that AtGAT1 (At1g08230) codes for an H(+)-driven, high affinity gamma-aminobutyric acid (GABA) transporter. In addition to GABA, other omega-aminofatty acids and butylamine are recognized. In contrast to the most closely related proteins of the proline transporter family, proline and glycine betaine are not transported by AtGAT1. AtGAT1 does not share sequence similarity with any of the non-plant GABA transporters described so far, and analyses of substrate selectivity and kinetic properties showed that AtGAT1-mediated transport is similar but distinct from that of mammalian, bacterial, and S. cerevisiae GABA transporters. Consistent with a role in GABA uptake into cells, transient expression of AtGAT1/green fluorescent protein fusion proteins in tobacco protoplasts revealed localization at the plasma membrane. In planta, AtGAT1 expression was highest in flowers and under conditions of elevated GABA concentrations such as wounding or senescence.
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Affiliation(s)
- Andreas Meyer
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Sepehr Eskandari
- Biological Sciences Department, California State Polytechnic University, Pomona, California 91768-4032
| | - Silke Grallath
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Doris Rentsch
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
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43
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Sellick CA, Reece RJ. Eukaryotic transcription factors as direct nutrient sensors. Trends Biochem Sci 2005; 30:405-12. [PMID: 15950477 DOI: 10.1016/j.tibs.2005.05.007] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Revised: 05/03/2005] [Accepted: 05/24/2005] [Indexed: 11/23/2022]
Abstract
The recognition of changes in environmental conditions, and the ability to adapt to these changes, is essential for the viability of cells. There are numerous well-characterized systems by which the presence or absence of an individual metabolite can be recognized by a cell. The recognition of a metabolite is, however, just one step of a process that often results in changes in the expression of sets of genes required to respond to that metabolite. The signalling pathway between metabolite recognition and transcriptional control is often complex. However, recent evidence from yeast suggests that complex signalling pathways might be circumvented via the direct interaction between individual metabolites and regulators of RNA polymerase II transcription.
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Affiliation(s)
- Christopher A Sellick
- The University of Manchester, Faculty of Life Sciences, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
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44
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Delroisse JM, Dannau M, Gilsoul JJ, El Mejdoub T, Destain J, Portetelle D, Thonart P, Haubruge E, Vandenbol M. Expression of a synthetic gene encoding a Tribolium castaneum carboxylesterase in Pichia pastoris. Protein Expr Purif 2005; 42:286-94. [PMID: 15946860 DOI: 10.1016/j.pep.2005.04.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Revised: 04/19/2005] [Accepted: 04/19/2005] [Indexed: 11/15/2022]
Abstract
This is the first report of an insect esterase efficiently expressed in the methylotrophic yeast Pichia pastoris (so far insect esterases have been produced only in the baculovirus system). Having isolated a Tribolium castaneum carboxylesterase cDNA (TCE), we were initially unable to express it in Escherichia coli or P. pastoris despite significant transcription levels. As codon usage bias is different in T. castaneum and P. pastoris, we assumed this was a possible explanation for the translational barrier observed in yeast. Accordingly, we designed and constructed by recursive PCR a synthetic TCE gene (synTCE) optimized for heterologous expression in P. pastoris, i.e., a gene in which certain TCE codons are replaced with synonymous codons 'preferred' in P. pastoris. When the altered gene was placed under the control of either the P. pastoris glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter or the inducible alcohol oxidase (AOX1) promoter and introduced on an expression vector into P. pastoris, its product was produced intracellularly. We also successfully explored the possibility of obtaining a secreted product: P. pastoris cells expressing an in-frame fusion of synTCE with the alpha-factor secretion signal under the control of the GAP promoter were found to secrete the recombinant esterase into the external medium (to a concentration of 7 mg/L). In addition to this demonstration of TCE production in yeast, our results suggest that the GAP promoter could advantageously replace the AOX1 promoter as a driver of synTCE expression. TCE specific activity was approximately 5 U/mg when p-nitrophenyl acetate was used as substrate.
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Affiliation(s)
- Jean-Marc Delroisse
- FUSAGX, Unité de Biologie animale et microbienne, Avenue Maréchal Juin, 6 B-5030 Gembloux, Belgium
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45
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Grallath S, Weimar T, Meyer A, Gumy C, Suter-Grotemeyer M, Neuhaus JM, Rentsch D. The AtProT family. Compatible solute transporters with similar substrate specificity but differential expression patterns. PLANT PHYSIOLOGY 2005; 137:117-26. [PMID: 15618414 PMCID: PMC548843 DOI: 10.1104/pp.104.055079] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Revised: 11/05/2004] [Accepted: 11/22/2004] [Indexed: 05/17/2023]
Abstract
Proline transporters (ProTs) mediate transport of the compatible solutes Pro, glycine betaine, and the stress-induced compound gamma-aminobutyric acid. A new member of this gene family, AtProT3, was isolated from Arabidopsis (Arabidopsis thaliana), and its properties were compared to AtProT1 and AtProT2. Transient expression of fusions of AtProT and the green fluorescent protein in tobacco (Nicotiana tabacum) protoplasts revealed that all three AtProTs were localized at the plasma membrane. Expression in a yeast (Saccharomyces cerevisiae) mutant demonstrated that the affinity of all three AtProTs was highest for glycine betaine (K(m) = 0.1-0.3 mM), lower for Pro (K(m) = 0.4-1 mM), and lowest for gamma-aminobutyric acid (K(m) = 4-5 mM). Relative quantification of the mRNA level using real-time PCR and analyses of transgenic plants expressing the beta-glucuronidase (uidA) gene under control of individual AtProT promoters showed that the expression pattern of AtProTs are complementary. AtProT1 expression was found in the phloem or phloem parenchyma cells throughout the whole plant, indicative of a role in long-distance transport of compatible solutes. beta-Glucuronidase activity under the control of the AtProT2 promoter was restricted to the epidermis and the cortex cells in roots, whereas in leaves, staining could be demonstrated only after wounding. In contrast, AtProT3 expression was restricted to the above-ground parts of the plant and could be localized to the epidermal cells in leaves. These results showed that, although intracellular localization, substrate specificity, and affinity are very similar, the transporters fulfill different roles in planta.
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Affiliation(s)
- Silke Grallath
- Institute of Plant Sciences, University of Bern, 3013 Bern, Switzerland
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46
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Lee YH, Tegeder M. Selective expression of a novel high-affinity transport system for acidic and neutral amino acids in the tapetum cells of Arabidopsis flowers. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 40:60-74. [PMID: 15361141 DOI: 10.1111/j.1365-313x.2004.02186.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Within the flower, microsporogenesis represents a major sink for nitrogen, but knowledge on how the imported nitrogen is transferred from the anther cell layers to developing pollen is lacking. Here, we provide information on characterization of a transporter (AtLHT2) that might play an important role in partitioning of amino acids for microspore development. Biochemical analysis in yeast showed that AtLHT2 transports proline and aspartate with high affinity. However, other neutral and acidic amino acids act as strong competitors for proline and aspartate uptake indicating that AtLHT2 generally transports uncharged and negatively charged amino acids. Comparison of the apparent K(m) values of AtLHT2 with previously characterized amino acid transporters clearly demonstrated that AtLHT2 represents a novel high-affinity system for neutral and acidic amino acids. Northern blot analysis showed strong expression of the amino acid transporter in flower buds. Cellular expression could be resolved by using RNA in situ hybridization and in situ RT-PCR methods, which localized AtLHT2 specifically to the tapetum tissue of the anthers. Developing pollen grains are symplasmically isolated from the sporophytic tissue and rely on the nutrients and other compounds secreted from the tapetum cells. Thus, the functional characterization of AtLHT2, together with our expression and localization studies, strongly suggest that in Arabidopsis flowers, AtLHT2 has a critical function in import of neutral and acidic amino acids into the tapetum cells for synthesis of compounds important for microspore structure and in transfer of organic nitrogen to the locule for pollen development.
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Affiliation(s)
- Yong-Hwa Lee
- School of Biological Sciences, Center for Reproductive Biology, Center for Integrated Biotechnology, Washington State University, Pullman, WA 99164-4236, USA
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47
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Römer U, Schrader H, Günther N, Nettelstroth N, Frommer WB, Elling L. Expression, purification and characterization of recombinant sucrose synthase 1 from Solanum tuberosum L. for carbohydrate engineering. J Biotechnol 2004; 107:135-49. [PMID: 14711497 DOI: 10.1016/j.jbiotec.2003.10.017] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The gene sus1 from Solanum tuberosum L. encoding for sucrose synthase 1 was cloned into the plasmid pDR195 under the control of the PMA1 promotor. After transformation of Saccharomyces cerevisiae strain 22574d sus1 was constitutively expressed giving a specific activity of 0.3Umg(-1) protein in the crude extract. A one-step purification by Q-Sepharose resulted in an 14-fold purified enzyme preparation in 74% yield. SuSy1 was subsequently purified by immobilized metal ion affinity chromatography and characterized for its utilization in synthesizing different nucleotide sugars and sucrose analogues. The kinetic constants for the cleavage and synthesis reaction were determined: K(m) (UDP) 4microM; K(iS) (UDP) 0.11mM; K(m) (sucrose) 91.6mM; K(m) (UDP-Glc) 0.5mM; K(iS) (UDP-Glc) 2.3mM; K(m) (D-fructose) 2.1mM; K(iS) (D-fructose) 35.9mM. Different nucleoside diphosphates as well as different donor substrate were accepted as follows: UDP>dTDP>ADP>CDP>GDP in the cleavage reaction and UDP-Glc>dTDP-Glc>ADP-Glc>CDP-Glc in the synthesis reaction. SuSy1 shows also a broad acceptance of D- and L-ketoses and D- and L-aldoses. The acceptance of aldoses was deduced from the binding of the inhibitor 5-deoxy-D-fructose (K(i) 0.3mM), an analogue of the natural substrate D-fructopyranoside. The broad substrate spectrum renders SuSy1 from potato a versatile biocatalyst for carbohydrate engineering.
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Affiliation(s)
- Ulrike Römer
- Department of Biotechnology/Biomaterial Sciences, Helmholtz-Institute for Biomedical Engineering, RWTH Aachen, Germany
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48
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Saxena D, Kannan KB, Brandriss MC. Rapamycin treatment results in GATA factor-independent hyperphosphorylation of the proline utilization pathway activator in Saccharomyces cerevisiae. EUKARYOTIC CELL 2003; 2:552-9. [PMID: 12796300 PMCID: PMC161436 DOI: 10.1128/ec.2.3.552-559.2003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Treatment of Saccharomyces cerevisiae cells with the immunosuppressive drug rapamycin results in a variety of cellular changes in response to perceived nutrient deprivation. Among other effects, rapamycin treatment results in the nuclear localization of the global nitrogen activators Gln3p and Nil1p/Gat1p, which leads to expression of nitrogen assimilation genes. The proline utilization (Put) pathway genes were shown to be among the genes induced by rapamycin. Having previously shown that the Put pathway activator Put3p is differentially phosphorylated in response to the quality of the nitrogen source, we examined the phosphorylation status of Put3p after rapamycin treatment. Treatment with rapamycin resulted in the hyperphosphorylation of Put3p, which was independent of Gln3p, Nil1p, and Ure2p. The relative contributions of global nitrogen (Gln3p and Nil1p) and pathway-specific (Put3p) activators to rapamycin-induced expression of the target gene PUT1 were also examined. We found that Nil1p and Put3p, but not Gln3p, play major roles in rapamycin-induced PUT1 expression. Our findings show that perceived nitrogen deprivation triggered by rapamycin treatment and steady-state growth in nitrogen-derepressing conditions are associated with hyperphosphorylation of Put3p and increased PUT1 expression. Rapamycin treatment and nitrogen derepression may share some, but not all, regulatory elements, since Gln3p and Nil1p do not participate identically in both processes and are not required for hyperphosphorylation. A complex relationship exists among the global and pathway-specific regulators, depending on the nature and quality of the nitrogen source.
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Affiliation(s)
- Deepti Saxena
- Department of Microbiology and Molecular Genetics, UMDNJ-New Jersey Medical School, Newark 07101-1709, USA
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49
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Trip H, Evers ME, Konings WN, Driessen AJM. Cloning and characterization of an aromatic amino acid and leucine permease of Penicillium chrysogenum. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1565:73-80. [PMID: 12225854 DOI: 10.1016/s0005-2736(02)00510-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The gene encoding the amino acid permease ArlP (Aromatic and leucine Permease) was isolated from the filamentous fungus Penicillium chrysogenum after PCR using degenerated oligonucleotides based on conserved regions of fungal amino acid permeases. The cDNA clone was used for expression of the permease in Saccharomyces cerevisiae M4054, which is defective in the general amino acid permease Gap1. Upon overexpression, an increase in the uptake of L-tyrosine, L-phenylalanine, L-tryptophan and L-leucine was observed. Further competition experiments indicate that ArlP recognizes neutral and aromatic amino acids with an unbranched beta-carbon atom.
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Affiliation(s)
- Hein Trip
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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50
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Struck C, Ernst M, Hahn M. Characterization of a developmentally regulated amino acid transporter (AAT1p) of the rust fungus Uromyces fabae. MOLECULAR PLANT PATHOLOGY 2002; 3:23-30. [PMID: 20569305 DOI: 10.1046/j.1464-6722.2001.00091.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
summary In the rust fungus Uromyces fabae, invasion of the host plant and haustorium formation are accompanied by the activation of many genes (PIGs =in planta induced genes). In addition to the previously described AAT2 (PIG2), AAT1 (PIG27) was found to encode a protein with a high similarity to fungal amino acid permeases. AAT1 transcripts are present in germinated hyphae and throughout the mycelium later in the infection process, but occur at the highest levels in haustoria. Expression of AAT1p in a histidine uptake-defective yeast mutant revealed energy-dependent transport of (14)C-histidine, with a K(M) value of 25.8 microm. In addition, complementation analysis revealed AAT1-dependent transport for lysine. Using Xenopus oocytes as expression system, AAT1p-dependent symport of protons with a broad spectrum of amino acids was observed, with the highest activities obtained with histidine and lysine. These results confirm that in rust fungi, the expression of amino acid transporters is developmentally regulated and occurs preferentially in the parasitic phase of development.
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Affiliation(s)
- Christine Struck
- Fachbereich Biologie, Universität Konstanz, 78457 Konstanz, Germany
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