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Betz R, Heidt S, Figueira-Galán D, Hartmann M, Langner T, Requena N. Alternative splicing regulation in plants by SP7-like effectors from symbiotic arbuscular mycorrhizal fungi. Nat Commun 2024; 15:7107. [PMID: 39160162 PMCID: PMC11333574 DOI: 10.1038/s41467-024-51512-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 08/08/2024] [Indexed: 08/21/2024] Open
Abstract
Most plants in natural ecosystems associate with arbuscular mycorrhizal (AM) fungi to survive soil nutrient limitations. To engage in symbiosis, AM fungi secrete effector molecules that, similar to pathogenic effectors, reprogram plant cells. Here we show that the Glomeromycotina-specific SP7 effector family impacts on the alternative splicing program of their hosts. SP7-like effectors localize at nuclear condensates and interact with the plant mRNA processing machinery, most prominently with the splicing factor SR45 and the core splicing proteins U1-70K and U2AF35. Ectopic expression of these effectors in the crop plant potato and in Arabidopsis induced developmental changes that paralleled to the alternative splicing modulation of a specific subset of genes. We propose that SP7-like proteins act as negative regulators of SR45 to modulate the fate of specific mRNAs in arbuscule-containing cells. Unraveling the communication mechanisms between symbiotic fungi and their host plants will help to identify targets to improve plant nutrition.
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Affiliation(s)
- Ruben Betz
- Joseph Kölreuter Institute for Plant Sciences. Molecular Phytopathology Department, Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4, Karlsruhe, Germany
| | - Sven Heidt
- Joseph Kölreuter Institute for Plant Sciences. Molecular Phytopathology Department, Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4, Karlsruhe, Germany
| | - David Figueira-Galán
- Joseph Kölreuter Institute for Plant Sciences. Molecular Phytopathology Department, Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4, Karlsruhe, Germany
| | - Meike Hartmann
- Joseph Kölreuter Institute for Plant Sciences. Molecular Phytopathology Department, Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4, Karlsruhe, Germany
| | - Thorsten Langner
- Max Planck Institute for Biology Tübingen - Max-Planck-Ring 5, Tübingen, Germany
| | - Natalia Requena
- Joseph Kölreuter Institute for Plant Sciences. Molecular Phytopathology Department, Karlsruhe Institute of Technology (KIT) - South Campus, Fritz-Haber-Weg 4, Karlsruhe, Germany.
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2
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Fanara S, Schloesser M, Joris M, De Franco S, Vandevenne M, Kerff F, Hanikenne M, Motte P. The Arabidopsis SR45 splicing factor bridges the splicing machinery and the exon-exon junction complex. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:2280-2298. [PMID: 38180875 DOI: 10.1093/jxb/erae002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 01/04/2024] [Indexed: 01/07/2024]
Abstract
The Arabidopsis splicing factor serine/arginine-rich 45 (SR45) contributes to several biological processes. The sr45-1 loss-of-function mutant exhibits delayed root development, late flowering, unusual numbers of floral organs, shorter siliques with decreased seed sets, narrower leaves and petals, and altered metal distribution. SR45 bears a unique RNA recognition motif (RRM) flanked by one serine/arginine-rich (RS) domain on both sides. Here, we studied the function of each SR45 domains by examining their involvement in: (i) the spatial distribution of SR45; (ii) the establishment of a protein-protein interaction network including spliceosomal and exon-exon junction complex (EJC) components; and (iii) the RNA binding specificity. We report that the endogenous SR45 promoter is active during vegetative and reproductive growth, and that the SR45 protein localizes in the nucleus. We demonstrate that the C-terminal arginine/serine-rich domain is a determinant of nuclear localization. We show that the SR45 RRM domain specifically binds purine-rich RNA motifs via three residues (H101, H141, and Y143), and is also involved in protein-protein interactions. We further show that SR45 bridges both mRNA splicing and surveillance machineries as a partner of EJC core components and peripheral factors, which requires phosphoresidues probably phosphorylated by kinases from both the CLK and SRPK families. Our findings provide insights into the contribution of each SR45 domain to both spliceosome and EJC assemblies.
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Affiliation(s)
- Steven Fanara
- InBioS-PhytoSystems, Functional Genomics and Plant Molecular Imaging, University of Liège, 4000, Liège, Belgium
| | - Marie Schloesser
- InBioS-PhytoSystems, Functional Genomics and Plant Molecular Imaging, University of Liège, 4000, Liège, Belgium
| | - Marine Joris
- InBioS-PhytoSystems, Functional Genomics and Plant Molecular Imaging, University of Liège, 4000, Liège, Belgium
| | - Simona De Franco
- InBioS-Center for Protein Engineering, Laboratory of Biological Macromolecules, University of Liège, 4000, Liège, Belgium
| | - Marylène Vandevenne
- InBioS-Center for Protein Engineering, Laboratory of Biological Macromolecules, University of Liège, 4000, Liège, Belgium
| | - Frédéric Kerff
- InBioS-Center for Protein Engineering, Laboratory of Crystallography, University of Liège, 4000, Liège, Belgium
| | - Marc Hanikenne
- InBioS-PhytoSystems, Translational Plant Biology, University of Liège, 4000, Liège, Belgium
| | - Patrick Motte
- InBioS-PhytoSystems, Functional Genomics and Plant Molecular Imaging, University of Liège, 4000, Liège, Belgium
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3
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Dwivedi SL, Quiroz LF, Reddy ASN, Spillane C, Ortiz R. Alternative Splicing Variation: Accessing and Exploiting in Crop Improvement Programs. Int J Mol Sci 2023; 24:15205. [PMID: 37894886 PMCID: PMC10607462 DOI: 10.3390/ijms242015205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Revised: 10/09/2023] [Accepted: 10/10/2023] [Indexed: 10/29/2023] Open
Abstract
Alternative splicing (AS) is a gene regulatory mechanism modulating gene expression in multiple ways. AS is prevalent in all eukaryotes including plants. AS generates two or more mRNAs from the precursor mRNA (pre-mRNA) to regulate transcriptome complexity and proteome diversity. Advances in next-generation sequencing, omics technology, bioinformatics tools, and computational methods provide new opportunities to quantify and visualize AS-based quantitative trait variation associated with plant growth, development, reproduction, and stress tolerance. Domestication, polyploidization, and environmental perturbation may evolve novel splicing variants associated with agronomically beneficial traits. To date, pre-mRNAs from many genes are spliced into multiple transcripts that cause phenotypic variation for complex traits, both in model plant Arabidopsis and field crops. Cataloguing and exploiting such variation may provide new paths to enhance climate resilience, resource-use efficiency, productivity, and nutritional quality of staple food crops. This review provides insights into AS variation alongside a gene expression analysis to select for novel phenotypic diversity for use in breeding programs. AS contributes to heterosis, enhances plant symbiosis (mycorrhiza and rhizobium), and provides a mechanistic link between the core clock genes and diverse environmental clues.
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Affiliation(s)
| | - Luis Felipe Quiroz
- Agriculture and Bioeconomy Research Centre, Ryan Institute, University of Galway, University Road, H91 REW4 Galway, Ireland
| | - Anireddy S N Reddy
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Charles Spillane
- Agriculture and Bioeconomy Research Centre, Ryan Institute, University of Galway, University Road, H91 REW4 Galway, Ireland
| | - Rodomiro Ortiz
- Department of Plant Breeding, Swedish University of Agricultural Sciences, 23053 Alnarp, SE, Sweden
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4
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de Luxán-Hernández C, Lohmann J, Tranque E, Chumova J, Binarova P, Salinas J, Weingartner M. MDF is a conserved splicing factor and modulates cell division and stress response in Arabidopsis. Life Sci Alliance 2022; 6:6/1/e202201507. [PMID: 36265897 PMCID: PMC9585968 DOI: 10.26508/lsa.202201507] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 09/27/2022] [Accepted: 09/27/2022] [Indexed: 02/05/2023] Open
Abstract
The coordination of cell division with stress response is essential for maintaining genome stability in plant meristems. Proteins involved in pre-mRNA splicing are important for these processes in animal and human cells. Based on its homology to the splicing factor SART1, which is implicated in the control of cell division and genome stability in human cells, we analyzed if MDF has similar functions in plants. We found that MDF associates with U4/U6.U5 tri-snRNP proteins and is essential for correct splicing of 2,037 transcripts. Loss of MDF function leads to cell division defects and cell death in meristems and was associated with up-regulation of stress-induced genes and down-regulation of mitotic regulators. In addition, the mdf-1 mutant is hypersensitive to DNA damage treatment supporting its role in coordinating stress response with cell division. Our analysis of a dephosphomutant of MDF suggested how its protein activity might be controlled. Our work uncovers the conserved function of a plant splicing factor and provides novel insight into the interplay of pre-mRNA processing and genome stability in plants.
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Affiliation(s)
| | - Julia Lohmann
- Institute of Plant Sciences and Microbiology, University of Hamburg, Hamburg, Germany
| | - Eduardo Tranque
- Departamento de Biotecnología Microbiana y de Plantas, Centro de Investigaciones Biológicas “Margarita Salas” (CSIC), Madrid, Spain
| | - Jana Chumova
- Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Pavla Binarova
- Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Julio Salinas
- Departamento de Biotecnología Microbiana y de Plantas, Centro de Investigaciones Biológicas “Margarita Salas” (CSIC), Madrid, Spain
| | - Magdalena Weingartner
- Institute of Plant Sciences and Microbiology, University of Hamburg, Hamburg, Germany
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5
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Albaqami M, Laluk K, Reddy ASN. The Arabidopsis splicing regulator SR45 confers salt tolerance in a splice isoform-dependent manner. PLANT MOLECULAR BIOLOGY 2019; 100:379-390. [PMID: 30968308 DOI: 10.1007/s11103-019-00864-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 03/28/2019] [Indexed: 05/08/2023]
Abstract
Functions of most splice isoforms that are generated by alternative splicing are unknown. We show that two splice variants that encode proteins differing in only eight amino acids have distinct functions in a stress response. Serine/arginine-rich (SR) and SR-like proteins, a conserved family of RNA binding proteins across eukaryotes, play important roles in pre-mRNA splicing and other post-transcriptional processes. Pre-mRNAs of SR and SR-like proteins undergo extensive alternative splicing in response to diverse stresses and produce multiple splice isoforms. However, the functions of most splice isoforms remain elusive. Alternative splicing of pre-mRNA of Arabidopsis SR45, which encodes an SR-like splicing regulator, generates two isoforms (long-SR45.1 and short-SR45.2). The proteins encoded by these two isoforms differ in eight amino acids. Here, we investigated the role of SR45 and its splice variants in salt stress tolerance. The loss of SR45 resulted in enhanced sensitivity to salt stress and changes in expression and splicing of genes involved in regulating salt stress response. Interestingly, only the long isoform (SR45.1) rescued the salt-sensitive phenotype as well as the altered gene expression and splicing patterns in the mutant. These results suggest that SR45 positively regulates salt tolerance. Furthermore, only the long isoform is required for SR45-mediated salt tolerance.
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Affiliation(s)
- Mohammed Albaqami
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, 80523, USA
- Department of Biology, Faculty of Applied Science, Umm Al-Qura University, Mecca, 21955, Kingdom of Saudi Arabia
| | - K Laluk
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, 80523, USA
| | - Anireddy S N Reddy
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, 80523, USA.
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6
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Voß S, Betz R, Heidt S, Corradi N, Requena N. RiCRN1, a Crinkler Effector From the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis, Functions in Arbuscule Development. Front Microbiol 2018; 9:2068. [PMID: 30233541 PMCID: PMC6131194 DOI: 10.3389/fmicb.2018.02068] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 08/13/2018] [Indexed: 01/10/2023] Open
Abstract
Arbuscular mycorrhizal (AM) symbiosis is one of the most prominent and beneficial plant–microbe interactions that facilitates mineral nutrition and confers tolerance to biotic and abiotic stresses. AM fungi colonize the root cortex and develop specialized structures called arbuscules where the nutrient exchange takes place. Arbuscule development is a highly controlled and coordinated process requiring the involvement of many plant proteins recruited at that interface. In contrast, much less is known about the fungal proteins involved in this process. Here, we have identified an AM fungal effector that participates in this developmental step of the symbiosis. RiCRN1 is a crinkler (CRN) effector that belongs to a subfamily of secreted CRN proteins from R. irregularis. CRNs have been so far only functionally characterized in pathogenic microbes and shown to participate in processes controlling plant cell death and immunity. RiCRN1 accumulates during symbiosis establishment parallel to MtPT4, the gene coding for an arbuscule-specific phosphate transporter. Expression in Nicotiana benthamiana leaves and in Medicago truncatula roots suggest that RiCRN1 is not involved in cell death processes. RiCRN1 dimerizes and localizes to nuclear bodies, suggesting that, similar to other CRNs, it functions in the plant nucleus. Downregulation of RiCRN1 using host-induced gene silencing led to an impairment of the symbiosis in M. truncatula and to a reduction of MtPT4, while ectopic expression of RiCRN1, surprisingly, led to a drastic reduction in arbuscule size that correlated with a decrease not only in MtPT4 but also in MtBCP1, a marker for initial stages of arbuscule development. Altogether, our results suggest that a tightly regulated expression in time and space of RiCRN1 is critical for symbiosis progression and for the proper initiation of arbuscule development.
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Affiliation(s)
- Stefanie Voß
- Molecular Phytopathology, Botanical Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Ruben Betz
- Molecular Phytopathology, Botanical Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Sven Heidt
- Molecular Phytopathology, Botanical Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Nicolas Corradi
- Department of Biology, Canadian Institute for Advanced Research, University of Ottawa, Ottawa, ON, Canada
| | - Natalia Requena
- Molecular Phytopathology, Botanical Institute, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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7
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Carvalho RF, Szakonyi D, Simpson CG, Barbosa ICR, Brown JWS, Baena-González E, Duque P. The Arabidopsis SR45 Splicing Factor, a Negative Regulator of Sugar Signaling, Modulates SNF1-Related Protein Kinase 1 Stability. THE PLANT CELL 2016; 28:1910-25. [PMID: 27436712 PMCID: PMC5006706 DOI: 10.1105/tpc.16.00301] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 07/05/2016] [Accepted: 07/19/2016] [Indexed: 05/19/2023]
Abstract
The ability to sense and respond to sugar signals allows plants to cope with environmental and metabolic changes by adjusting growth and development accordingly. We previously reported that the SR45 splicing factor negatively regulates glucose signaling during early seedling development in Arabidopsis thaliana Here, we show that under glucose-fed conditions, the Arabidopsis sr45-1 loss-of-function mutant contains higher amounts of the energy-sensing SNF1-Related Protein Kinase 1 (SnRK1) despite unaffected SnRK1 transcript levels. In agreement, marker genes for SnRK1 activity are upregulated in sr45-1 plants, and the glucose hypersensitivity of sr45-1 is attenuated by disruption of the SnRK1 gene. Using a high-resolution RT-PCR panel, we found that the sr45-1 mutation broadly targets alternative splicing in vivo, including that of the SR45 pre-mRNA itself. Importantly, the enhanced SnRK1 levels in sr45-1 are suppressed by a proteasome inhibitor, indicating that SR45 promotes targeting of the SnRK1 protein for proteasomal destruction. Finally, we demonstrate that SR45 regulates alternative splicing of the Arabidopsis 5PTase13 gene, which encodes an inositol polyphosphate 5-phosphatase previously shown to interact with and regulate the stability of SnRK1 in vitro, thus providing a mechanistic link between SR45 function and the modulation of degradation of the SnRK1 energy sensor in response to sugars.
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Affiliation(s)
| | - Dóra Szakonyi
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal
| | - Craig G Simpson
- The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland, United Kingdom
| | | | - John W S Brown
- The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland, United Kingdom University of Dundee at The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland, United Kingdom
| | | | - Paula Duque
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal
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8
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Xing D, Wang Y, Hamilton M, Ben-Hur A, Reddy ASN. Transcriptome-Wide Identification of RNA Targets of Arabidopsis SERINE/ARGININE-RICH45 Uncovers the Unexpected Roles of This RNA Binding Protein in RNA Processing. THE PLANT CELL 2015; 27:3294-308. [PMID: 26603559 PMCID: PMC4707455 DOI: 10.1105/tpc.15.00641] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 10/19/2015] [Accepted: 11/03/2015] [Indexed: 05/20/2023]
Abstract
Plant SR45 and its metazoan ortholog RNPS1 are serine/arginine-rich (SR)-like RNA binding proteins that function in splicing/postsplicing events and regulate diverse processes in eukaryotes. Interactions of SR45 with both RNAs and proteins are crucial for regulating RNA processing. However, in vivo RNA targets of SR45 are currently unclear. Using RNA immunoprecipitation followed by high-throughput sequencing, we identified over 4000 Arabidopsis thaliana RNAs that directly or indirectly associate with SR45, designated as SR45-associated RNAs (SARs). Comprehensive analyses of these SARs revealed several roles for SR45. First, SR45 associates with and regulates the expression of 30% of abscisic acid (ABA) signaling genes at the postsplicing level. Second, although most SARs are derived from intron-containing genes, surprisingly, 340 SARs are derived from intronless genes. Expression analysis of the SARs suggests that SR45 differentially regulates intronless and intron-containing SARs. Finally, we identified four overrepresented RNA motifs in SARs that likely mediate SR45's recognition of its targets. Therefore, SR45 plays an unexpected role in mRNA processing of intronless genes, and numerous ABA signaling genes are targeted for regulation at the posttranscriptional level. The diverse molecular functions of SR45 uncovered in this study are likely applicable to other species in view of its conservation across eukaryotes.
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Affiliation(s)
- Denghui Xing
- Department of Biology and Program in Molecular Plant Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Yajun Wang
- Department of Biology and Program in Molecular Plant Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Michael Hamilton
- Computer Science Department, Colorado State University, Fort Collins, Colorado 80523
| | - Asa Ben-Hur
- Computer Science Department, Colorado State University, Fort Collins, Colorado 80523
| | - Anireddy S N Reddy
- Department of Biology and Program in Molecular Plant Biology, Colorado State University, Fort Collins, Colorado 80523
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9
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Zhang XN, Mo C, Garrett WM, Cooper B. Phosphothreonine 218 is required for the function of SR45.1 in regulating flower petal development in Arabidopsis. PLANT SIGNALING & BEHAVIOR 2014; 9:e29134. [PMID: 25763493 PMCID: PMC4203572 DOI: 10.4161/psb.29134] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 05/19/2023]
Abstract
RNA splicing is crucial to the production of mature mRNAs (mRNA). In Arabidopsis thaliana, the protein Arginine/Serine-rich 45 (SR45) acts as an RNA splicing activator and initiates the spliceosome assembly. SR45 is alternatively spliced into 2 isoforms. Isoform 1 (SR45.1) plays an important role in the flower petal development whereas isoform 2 (SR45.2) is important for root growth. In this study, we used immunoprecipitation to isolate an SR45.1-GFP fusion protein from transgenic plants complementing a null mutant, sr45-1. Mass spectrometry suggested a single phosphorylation event in a peptide from the alternatively spliced region unique to SR45.1. Substituting alanine for threonine 218, a candidate site for phosphorylation, did not complement the sr45-1 mutant with narrow flower petals whereas substituting aspartic acid or glutamic acid for threonine 218 did complement the sr45-1 mutant. Mass spectrometry also revealed that other proteins involved in the spliceosome co-precipitated with SR45.1, and RT-qPCR revealed that phosphorylation of threonine 218 promotes the function of SR45.1 in promoting the constitutive splicing of SR30 mRNA. This is the first demonstration of a specific phosphorylation site that differentially regulates the function of a plant splicing activator in physiologically and morphologically distinct plant tissues.
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Affiliation(s)
- Xiao-Ning Zhang
- Department of Biology; Saint Bonaventure University; Saint Bonaventure, NY USA
- Correspondence to: Xiao-Ning Zhang,
| | - Cecilia Mo
- Department of Biology; Saint Bonaventure University; Saint Bonaventure, NY USA
| | - Wesley M Garrett
- Animal Biosciences and Biotechnology Laboratory; USDA-ARS; Beltsville, MD USA
| | - Bret Cooper
- Soybean Genomics and Improvement Laboratory; USDA-ARS; Beltsville, MD USA
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10
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Carvalho RF, Feijão CV, Duque P. On the physiological significance of alternative splicing events in higher plants. PROTOPLASMA 2013; 250:639-50. [PMID: 22961303 DOI: 10.1007/s00709-012-0448-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Accepted: 08/16/2012] [Indexed: 05/05/2023]
Abstract
Alternative splicing, which generates multiple transcripts from the same gene and potentially different protein isoforms, is a key posttranscriptional regulatory mechanism for expanding proteomic diversity and functional complexity in higher eukaryotes. The most recent estimates, based on whole transcriptome sequencing, indicate that about 95 % of human and 60 % of Arabidopsis multi-exon genes undergo alternative splicing, suggesting important roles for this mechanism in biological processes. However, while the misregulation of alternative splicing has been associated with many human diseases, its biological relevance in plant systems is just beginning to unfold. We review here the few plant genes for which the production of multiple splice isoforms has been reported to have a clear in vivo functional impact. These case studies implicate alternative splicing in the control of a wide range of physiological and developmental processes, including photosynthetic and starch metabolism, hormone signaling, seed germination, root growth and flowering, as well as in biotic and abiotic stress responses. Future functional characterization of alternative splicing events and identification of the transcripts targeted by major regulators of this versatile means of modulating gene expression should uncover the breadth of its physiological significance in higher plants.
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Affiliation(s)
- Raquel F Carvalho
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156, Oeiras, Portugal
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11
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Abstract
The passage of mRNA molecules from the site of synthesis, through the nucleoplasm and the nuclear pore, en route to the cytoplasm, might appear straightforward. Nonetheless, several decades of detailed examination of this pathway, from high resolution electron microscopy in fixed specimens, through the development of immuno-detection techniques and fluorescence toolkits, to the current era of live-cell imaging, show this to be an eventful journey. In addition to mRNAs, several species of noncoding RNAs travel and function in the nucleus, some being retained within throughout their lifetime. This review will highlight the nucleoplasmic paths taken by mRNAs and noncoding RNAs in eukaryotic cells with special focus on live-cell data and in concurrence with the biophysical nature of the nucleus.
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Affiliation(s)
- Jonathan Sheinberger
- The Mina & Everard Goodman Faculty of Life Sciences & Institute of Nanotechnology, Bar-Ilan University, Ramat Gan, Israel
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12
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Day IS, Golovkin M, Palusa SG, Link A, Ali GS, Thomas J, Richardson DN, Reddy ASN. Interactions of SR45, an SR-like protein, with spliceosomal proteins and an intronic sequence: insights into regulated splicing. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 71:936-47. [PMID: 22563826 DOI: 10.1111/j.1365-313x.2012.05042.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
SR45 is a serine/arginine-rich (SR)-like protein with two arginine/serine-rich (RS) domains. We have previously shown that SR45 regulates alternative splicing (AS) by differential selection of 5' and 3' splice sites. However, it is unknown how SR45 regulates AS. To gain mechanistic insights into the roles of SR45 in splicing, we screened a yeast two-hybrid library with SR45. This screening resulted in the isolation of two spliceosomal proteins, U1-70K and U2AF(35) b that are known to function in 5' and 3' splice site selection, respectively. This screen not only confirmed our prior observation that U1-70K and SR45 interact, but also helped to identify an additional interacting partner (U2AF(35) ). In vitro and in vivo analyses revealed an interaction of SR45 with both paralogs of U2AF(35) . Furthermore, we show that the RS1 and RS2 domains of SR45, and not the RNA recognition motif (RRM) domain, associate independently with both U2AF(35) proteins. Interaction studies among U2AF(35) paralogs and between U2AF(35) and U1-70K revealed that U2AF(35) can form homo- or heterodimers and that U2AF(35) proteins can associate with U1-70K. Using RNA probes from SR30 intron 10, whose splicing is altered in the sr45 mutant, we show that SR45 and U2AF(35) b bind to different parts of the intron, with a binding site for SR45 in the 5' region and two binding regions, each ending with a known 3' splice site, for U2AF(35) b. These results suggest that SR45 recruits U1snRNP and U2AF to 5' and 3' splice sites, respectively, by interacting with pre-mRNA, U1-70K and U2AF(35) and modulates AS.
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Affiliation(s)
- Irene S Day
- Department of Biology, Program in Molecular Plant Biology, Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
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13
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Niedojadło J, Mikulski Z, Dełeńko K, Szmidt-Jaworska A, Smoliński DJ, Epstein AL. The perichromatin region of the plant cell nucleus is the area with the strongest co-localisation of snRNA and SR proteins. PLANTA 2012; 236:715-726. [PMID: 22526497 PMCID: PMC3404291 DOI: 10.1007/s00425-012-1640-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 03/21/2012] [Indexed: 05/31/2023]
Abstract
The spatial organisation of the splicing system in plant cells containing either reticular (Allium cepa) or chromocentric (Lupinus luteus) nuclei was studied by immunolabelling of SR proteins, snRNA, and the PANA antigen, known markers for interchromatin granule clusters in mammalian cells. Electron microscope results allowed us to determine the distribution of these molecules within the structural domains of the nucleus. Similar to animal cells, in both plant species SR proteins were localised in interchromatin granules, but contrary to animal cells contained very small amounts of snRNA. The area with the strongest snRNA and SR protein co-localisation was the perichromatin region, which may be the location of pre-mRNA splicing in the plant cell nuclei. The only observable differences in the organisation of reticular and chromocentric nuclei were the size of the speckles and the number of snRNA pools in the condensed chromatin. We conclude that, despite remarkable changes in the nuclear architecture, the organisation of the splicing system is remarkably similar in both types of plant cell nuclei.
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Affiliation(s)
- Janusz Niedojadło
- Department of Cell Biology, Institute of General and Molecular Biology, Nicolaus Copernicus University, Ul. Gagarina 9, 87-100, Torun, Poland.
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Domozych DS. The quest for four-dimensional imaging in plant cell biology: it's just a matter of time. ANNALS OF BOTANY 2012; 110:461-74. [PMID: 22628381 PMCID: PMC3394652 DOI: 10.1093/aob/mcs107] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 04/04/2012] [Indexed: 05/22/2023]
Abstract
BACKGROUND Analysis of plant cell dynamics over time, or four-dimensional imaging (4-DI), represents a major goal of plant science. The ability to resolve structures in the third dimension within the cell or tissue during developmental events or in response to environmental or experimental stresses (i.e. 4-DI) is critical to our understanding of gene expression, post-expression modulations of macromolecules and sub-cellular system interactions. SCOPE Microscopy-based technologies have been profoundly integral to this type of investigation, and new and refined microscopy technologies now allow for the visualization of cell dynamics with unprecedented resolution, contrast and experimental versatility. However, certain realities of light and electron microscopy, choice of specimen and specimen preparation techniques limit the scope of readily attaining 4-DI. Today, the plant microscopist must use a combinatorial strategy whereby multiple microscopy-based investigations are used. Modern fluorescence, confocal laser scanning, transmission electron and scanning electron microscopy provide effective conduits for synthesizing data detailing live cell dynamics and highly resolved snapshots of specific cell structures that will ultimately lead to 4-DI. This review provides a synopsis of such technologies available.
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Affiliation(s)
- David S Domozych
- Department of Biology and Skidmore Microscopy Imaging Center, Skidmore College, Saratoga Springs, NY 12866, USA.
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15
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Reddy ASN, Day IS, Göhring J, Barta A. Localization and dynamics of nuclear speckles in plants. PLANT PHYSIOLOGY 2012; 158:67-77. [PMID: 22045923 PMCID: PMC3252098 DOI: 10.1104/pp.111.186700] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 10/31/2011] [Indexed: 05/17/2023]
Affiliation(s)
- Anireddy S N Reddy
- Department of Biology, Program in Molecular Plant Biology, Program in Cell and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
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16
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Agrawal GK, Bourguignon J, Rolland N, Ephritikhine G, Ferro M, Jaquinod M, Alexiou KG, Chardot T, Chakraborty N, Jolivet P, Doonan JH, Rakwal R. Plant organelle proteomics: collaborating for optimal cell function. MASS SPECTROMETRY REVIEWS 2011; 30:772-853. [PMID: 21038434 DOI: 10.1002/mas.20301] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Revised: 02/02/2010] [Accepted: 02/02/2010] [Indexed: 05/10/2023]
Abstract
Organelle proteomics describes the study of proteins present in organelle at a particular instance during the whole period of their life cycle in a cell. Organelles are specialized membrane bound structures within a cell that function by interacting with cytosolic and luminal soluble proteins making the protein composition of each organelle dynamic. Depending on organism, the total number of organelles within a cell varies, indicating their evolution with respect to protein number and function. For example, one of the striking differences between plant and animal cells is the plastids in plants. Organelles have their own proteins, and few organelles like mitochondria and chloroplast have their own genome to synthesize proteins for specific function and also require nuclear-encoded proteins. Enormous work has been performed on animal organelle proteomics. However, plant organelle proteomics has seen limited work mainly due to: (i) inter-plant and inter-tissue complexity, (ii) difficulties in isolation of subcellular compartments, and (iii) their enrichment and purity. Despite these concerns, the field of organelle proteomics is growing in plants, such as Arabidopsis, rice and maize. The available data are beginning to help better understand organelles and their distinct and/or overlapping functions in different plant tissues, organs or cell types, and more importantly, how protein components of organelles behave during development and with surrounding environments. Studies on organelles have provided a few good reviews, but none of them are comprehensive. Here, we present a comprehensive review on plant organelle proteomics starting from the significance of organelle in cells, to organelle isolation, to protein identification and to biology and beyond. To put together such a systematic, in-depth review and to translate acquired knowledge in a proper and adequate form, we join minds to provide discussion and viewpoints on the collaborative nature of organelles in cell, their proper function and evolution.
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Affiliation(s)
- Ganesh Kumar Agrawal
- Research Laboratory for Biotechnology and Biochemistry (RLABB), P.O. Box 13265, Sanepa, Kathmandu, Nepal.
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17
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Reddy ASN, Shad Ali G. Plant serine/arginine-rich proteins: roles in precursor messenger RNA splicing, plant development, and stress responses. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:875-89. [PMID: 21766458 DOI: 10.1002/wrna.98] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Global analyses of splicing of precursor messenger RNAs (pre-mRNAs) have revealed that alternative splicing (AS) is highly pervasive in plants. Despite the widespread occurrence of AS in plants, the mechanisms that control splicing and the roles of splice variants generated from a gene are poorly understood. Studies on plant serine/arginine-rich (SR) proteins, a family of highly conserved proteins, suggest their role in both constitutive splicing and AS of pre-mRNAs. SR proteins have a characteristic domain structure consisting of one or two RNA recognition motifs at the N-terminus and a C-terminal RS domain rich in arginine/serine dipeptides. Plants have many more SR proteins compared to animals including several plant-specific subfamilies. Pre-mRNAs of plant SR proteins are extensively alternatively spliced to increase the transcript complexity by about six-fold. Some of this AS is controlled in a tissue- and development-specific manner. Furthermore, AS of SR pre-mRNAs is altered by various stresses, raising the possibility of rapid reprogramming of the whole transcriptome by external signals through regulation of the splicing of these master regulators of splicing. Most SR splice variants contain a premature termination codon and are degraded by up-frameshift 3 (UPF3)-mediated nonsense-mediated decay (NMD), suggesting a link between NMD and regulation of expression of the functional transcripts of SR proteins. Limited functional studies with plant SRs suggest key roles in growth and development and plant responses to the environment. Here, we discuss the current status of research on plant SRs and some promising approaches to address many unanswered questions about plant SRs.
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Affiliation(s)
- Anireddy S N Reddy
- Department of Biology, Program in Molecular Plant Biology, Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, USA.
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Lummer M, Humpert F, Steuwe C, Caesar K, Schüttpelz M, Sauer M, Staiger D. Reversible Photoswitchable DRONPA-s Monitors Nucleocytoplasmic Transport of an RNA-Binding Protein in Transgenic Plants. Traffic 2011; 12:693-702. [DOI: 10.1111/j.1600-0854.2011.01180.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Huranová M, Ivani I, Benda A, Poser I, Brody Y, Hof M, Shav-Tal Y, Neugebauer KM, Stanek D. The differential interaction of snRNPs with pre-mRNA reveals splicing kinetics in living cells. ACTA ACUST UNITED AC 2010; 191:75-86. [PMID: 20921136 PMCID: PMC2953428 DOI: 10.1083/jcb.201004030] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
GFP-tagged snRNP components reveal the dynamics and rate for spliceosome assembly in vivo. Precursor messenger RNA (pre-mRNA) splicing is catalyzed by the spliceosome, a large ribonucleoprotein (RNP) complex composed of five small nuclear RNP particles (snRNPs) and additional proteins. Using live cell imaging of GFP-tagged snRNP components expressed at endogenous levels, we examined how the spliceosome assembles in vivo. A comprehensive analysis of snRNP dynamics in the cell nucleus enabled us to determine snRNP diffusion throughout the nucleoplasm as well as the interaction rates of individual snRNPs with pre-mRNA. Core components of the spliceosome, U2 and U5 snRNPs, associated with pre-mRNA for 15–30 s, indicating that splicing is accomplished within this time period. Additionally, binding of U1 and U4/U6 snRNPs with pre-mRNA occurred within seconds, indicating that the interaction of individual snRNPs with pre-mRNA is distinct. These results are consistent with the predictions of the step-wise model of spliceosome assembly and provide an estimate on the rate of splicing in human cells.
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Affiliation(s)
- Martina Huranová
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic
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Carvalho RF, Carvalho SD, Duque P. The plant-specific SR45 protein negatively regulates glucose and ABA signaling during early seedling development in Arabidopsis. PLANT PHYSIOLOGY 2010; 154:772-83. [PMID: 20699397 PMCID: PMC2949030 DOI: 10.1104/pp.110.155523] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 08/07/2010] [Indexed: 05/20/2023]
Abstract
The plant-specific SR45 belongs to the highly conserved family of serine/arginine-rich (SR) proteins, which play key roles in precursor-mRNA splicing and other aspects of RNA metabolism. An Arabidopsis (Arabidopsis thaliana) loss-of-function mutant, sr45-1, displays pleiotropic phenotypes, such as defects in flower and leaf morphology, root growth, and flowering time. Here, we show that the sr45-1 mutation confers hypersensitivity to glucose (Glc) during early seedling growth in Arabidopsis. Unlike wild-type plants, the sr45-1 mutant displays impaired cotyledon greening and expansion as well as reduced hypocotyl elongation of dark-grown seedlings when grown in the presence of low (3%) Glc concentrations. In addition, SR45 is involved in the control of Glc-responsive gene expression, as the mutant displays enhanced repression of photosynthetic and nitrogen metabolism genes and overinduction of starch and anthocyanin biosynthesis genes. Like many other sugar response mutants, sr45-1 also shows hypersensitivity to abscisic acid (ABA) but appears to be unaffected in ethylene signaling. Importantly, the sr45-1 mutant shows enhanced ability to accumulate ABA in response to Glc, and the ABA biosynthesis inhibitor fluridone partially rescues the sugar-mediated growth arrest. Moreover, three ABA biosynthesis genes and two key ABA signaling genes, ABI3 and ABI5, are markedly overinduced by Glc in sr45-1. These results provide evidence that the SR45 protein defines a novel player in plant sugar response that negatively regulates Glc signaling during early seedling development by down-regulating both Glc-specific ABA accumulation and ABA biosynthesis and signaling gene expression.
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Yang T, Shad Ali G, Yang L, Du L, Reddy ASN, Poovaiah BW. Calcium/calmodulin-regulated receptor-like kinase CRLK1 interacts with MEKK1 in plants. PLANT SIGNALING & BEHAVIOR 2010; 5:991-4. [PMID: 20724845 PMCID: PMC3115177 DOI: 10.4161/psb.5.8.12225] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 04/28/2010] [Indexed: 05/20/2023]
Abstract
Recently we reported that CRLK1, a novel calcium/calmodulin-regulated receptor-like kinase plays an important role in regulating plant cold tolerance. Calcium/calmodulin binds to CRLK1 and upregulates its activity. Gene knockout and complementation studies revealed that CRLK1 is a positive regulator of plant response to chilling and freezing temperatures. Here we show that MEKK1, a member of MAP kinase kinase kinase family, interacts with CRLK1 both in vitro and in planta. The cold triggered MAP kinase activation in wild-type plants was abolished in crlk1 knockout mutants. Similarly, the cold induced expression levels of genes involved in MAP kinase signaling are also altered in crlk1 mutants. These results suggest that calcium/calmodulin-regulated CRLK1 modulates cold acclimation through MAP kinase cascade in plants.
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Affiliation(s)
- Tianbao Yang
- Center for Integrated Biotechnology and Department of Horticulture, Washington State University, Pullman, WA, USA
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Rausin G, Tillemans V, Stankovic N, Hanikenne M, Motte P. Dynamic nucleocytoplasmic shuttling of an Arabidopsis SR splicing factor: role of the RNA-binding domains. PLANT PHYSIOLOGY 2010; 153:273-84. [PMID: 20237019 PMCID: PMC2862426 DOI: 10.1104/pp.110.154740] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 03/11/2010] [Indexed: 05/22/2023]
Abstract
Serine/arginine-rich (SR) proteins are essential nuclear-localized splicing factors. We have investigated the dynamic subcellular distribution of the Arabidopsis (Arabidopsis thaliana) RSZp22 protein, a homolog of the human 9G8 SR factor. Little is known about the determinants underlying the control of plant SR protein dynamics, and so far most studies relied on ectopic transient overexpression. Here, we provide a detailed analysis of the RSZp22 expression profile and describe its nucleocytoplasmic shuttling properties in specific cell types. Comparison of transient ectopic- and stable tissue-specific expression highlights the advantages of both approaches for nuclear protein dynamic studies. By site-directed mutagenesis of RSZp22 RNA-binding sequences, we show that functional RNA recognition motif RNP1 and zinc-knuckle are dispensable for the exclusive protein nuclear localization and speckle-like distribution. Fluorescence resonance energy transfer imaging also revealed that these motifs are implicated in RSZp22 molecular interactions. Furthermore, the RNA-binding motif mutants are defective for their export through the CRM1/XPO1/Exportin-1 receptor pathway but retain nucleocytoplasmic mobility. Moreover, our data suggest that CRM1 is a putative export receptor for mRNPs in plants.
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Zhang XN, Mount SM. Two alternatively spliced isoforms of the Arabidopsis SR45 protein have distinct roles during normal plant development. PLANT PHYSIOLOGY 2009; 150:1450-8. [PMID: 19403727 PMCID: PMC2705014 DOI: 10.1104/pp.109.138180] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 04/16/2009] [Indexed: 05/18/2023]
Abstract
The serine-arginine-rich (SR) proteins constitute a conserved family of pre-mRNA splicing factors. In Arabidopsis (Arabidopsis thaliana), they are encoded by 19 genes, most of which are themselves alternatively spliced. In the case of SR45, the use of alternative 3' splice sites 21 nucleotides apart generates two alternatively spliced isoforms. Isoform 1 (SR45.1) has an insertion relative to isoform 2 (SR45.2) that replaces a single arginine with eight amino acids (TSPQRKTG). The biological implications of SR45 alternative splicing have been unclear. A previously described loss-of-function mutant affecting both isoforms, sr45-1, shows several developmental defects, including defects in petal development and root growth. We found that the SR45 promoter is highly active in regions with actively growing and dividing cells. We also tested the ability of each SR45 isoform to complement the sr45-1 mutant by overexpression of isoform-specific green fluorescent protein (GFP) fusion proteins. As expected, transgenic plants overexpressing either isoform displayed both nuclear speckles and GFP fluorescence throughout the nucleoplasm. We found that SR45.1-GFP complements the flower petal phenotype, but not the root growth phenotype. Conversely, SR45.2-GFP complements root growth but not floral morphology. Mutation of a predicted phosphorylation site within the alternatively spliced segment, SR45.1-S219A-GFP, does not affect complementation. However, a double mutation affecting both serine-219 and the adjacent threonine-218 (SR45.1-T218A + S219A-GFP) behaves like isoform 2, complementing the root but not the floral phenotype. In conclusion, our study provides evidence that the two alternatively spliced isoforms of SR45 have distinct biological functions.
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Affiliation(s)
- Xiao-Ning Zhang
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20740, USA
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Tanabe N, Kimura A, Yoshimura K, Shigeoka S. Plant-specific SR-related protein atSR45a interacts with spliceosomal proteins in plant nucleus. PLANT MOLECULAR BIOLOGY 2009; 70:241-52. [PMID: 19238562 DOI: 10.1007/s11103-009-9469-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 02/08/2009] [Indexed: 05/08/2023]
Abstract
Serine/arginine-rich (SR) protein and its homologues (SR-related proteins) are important regulators of constitutive and/or alternative splicing and other aspects of mRNA metabolism. To clarify the contribution of a plant-specific and stress-responsive SR-related protein, atSR45a, to splicing events, here we analyzed the interaction of atSR45a with the other splicing factors by conducting a yeast two-hybrid assay and a bimolecular fluorescence complementation analysis. The atSR45a-1a and -2 proteins, the presumed mature forms produced by alternative splicing of atSR45a, interacted with U1-70K and U2AF(35)b, splicing factors for the initial definition of 5' and 3' splice sites, respectively, in the early stage of spliceosome assembly. Both proteins also interacted with themselves, other SR proteins (atSR45 and atSCL28), and PRP38-like protein, a homologue of the splicing factor essential for cleavage of the 5' splice site. The mapping of deletion mutants of atSR45a proteins revealed that the C-terminal arginine/serine-rich (RS) domain of atSR45a proteins are required for the interaction with U1-70K, U2AF(35)b, atSR45, atSCL28, PRP38-like protein, and themselves, and the N-terminal RS domain enhances the interaction efficiency. Interestingly, the distinctive N-terminal extension in atSR45a-1a protein, but not atSR45a-2 protein, inhibited the interaction with these splicing factors. These findings suggest that the atSR45a proteins help to form the bridge between 5' and 3' splice sites in the spliceosome assembly and the efficiency of spliceosome formation is affected by the expression ratio of atSR45a-1a and atSR45a-2.
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Affiliation(s)
- Noriaki Tanabe
- Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, Nakamachi, Nara, Japan
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Morell M, Ventura S, Avilés FX. Protein complementation assays: Approaches for the in vivo analysis of protein interactions. FEBS Lett 2009; 583:1684-91. [DOI: 10.1016/j.febslet.2009.03.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Accepted: 03/02/2009] [Indexed: 11/28/2022]
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Lorković ZJ, Barta A. Role of Cajal bodies and nucleolus in the maturation of the U1 snRNP in Arabidopsis. PLoS One 2008; 3:e3989. [PMID: 19098980 PMCID: PMC2600615 DOI: 10.1371/journal.pone.0003989] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 11/21/2008] [Indexed: 01/31/2023] Open
Abstract
Background The biogenesis of spliceosomal snRNPs takes place in both the cytoplasm where Sm core proteins are added and snRNAs are modified at the 5′ and 3′ termini and in the nucleus where snRNP-specific proteins associate. U1 snRNP consists of U1 snRNA, seven Sm proteins and three snRNP-specific proteins, U1-70K, U1A, and U1C. It has been shown previously that after import to the nucleus U2 and U4/U6 snRNP-specific proteins first appear in Cajal bodies (CB) and then in splicing speckles. In addition, in cells grown under normal conditions U2, U4, U5, and U6 snRNAs/snRNPs are abundant in CBs. Therefore, it has been proposed that the final assembly of these spliceosomal snRNPs takes place in this nuclear compartment. In contrast, U1 snRNA in both animal and plant cells has rarely been found in this nuclear compartment. Methodology/Principal Findings Here, we analysed the subnuclear distribution of Arabidopsis U1 snRNP-specific proteins fused to GFP or mRFP in transiently transformed Arabidopsis protoplasts. Irrespective of the tag used, U1-70K was exclusively found in the nucleus, whereas U1A and U1C were equally distributed between the nucleus and the cytoplasm. In the nucleus all three proteins localised to CBs and nucleoli although to different extent. Interestingly, we also found that the appearance of the three proteins in nuclear speckles differ significantly. U1-70K was mostly found in speckles whereas U1A and U1C in ∼90% of cells showed diffuse nucleoplasmic in combination with CBs and nucleolar localisation. Conclusions/Significance Our data indicate that CBs and nucleolus are involved in the maturation of U1 snRNP. Differences in nuclear accumulation and distribution between U1-70K and U1A and U1C proteins may indicate that either U1-70K or U1A and U1C associate with, or is/are involved, in other nuclear processes apart from pre-mRNA splicing.
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Affiliation(s)
- Zdravko J Lorković
- Department of Medical Biochemistry, Max F Perutz Laboratories, Medical University of Vienna, Vienna, Austria.
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