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Wiśniewska J, Kęsy J, Mucha N, Tyburski J. Auxin resistant 1 gene (AUX1) mediates auxin effect on Arabidopsis thaliana callus growth by regulating its content and distribution pattern. JOURNAL OF PLANT PHYSIOLOGY 2024; 293:154168. [PMID: 38176282 DOI: 10.1016/j.jplph.2023.154168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 12/28/2023] [Accepted: 12/29/2023] [Indexed: 01/06/2024]
Abstract
Callus sustained growth relies heavily on auxin, which is supplied to the culture medium. Surprisingly, there is a noticeable absence of information regarding the involvement of carrier-mediated auxin polar transport gene in callus growth regulation. Here, we delve into the role of the AUXIN RESISTANT 1 (AUX1) influx transporter in the regulation of callus growth, comparing the effects under conditions of light versus darkness. It was observed that callus growth was significantly enhanced under light illumination. This growth-stimulatory effect was accompanied by a decrease in the levels of free auxin within the callus cells when compared to conditions of darkness. In the aux1-22 mutant callus, which lacks functional AUX1, there was a substantial reduction in IAA levels. Nonetheless, the mutant callus exhibited markedly higher growth rates compared to the wild type. This suggests that the reduction in exogenous auxin uptake through the AUX1-dependent pathway may prevent the overaccumulation of growth-restricting hormone concentrations. The growth-stimulatory effect of AUX1 deficiency was counteracted by nonspecific auxin influx transport inhibitors. This finding shows that other auxin influx carriers likely play a role in facilitating the diffusion of auxin from the culture medium to sustain high growth rates. AUX1 was primarily localized in the plasma membranes of the two outermost cell layers of the callus clump and the parenchyma cells adjacent to tracheary elements. Significantly, these locations coincided with the regions of maximal auxin concentration. Consequently, it can be inferred that AUX1 mediates the auxin distribution within the callus.
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Affiliation(s)
- Justyna Wiśniewska
- Plant Physiology and Biotechnology Department, Nicolaus Copernicus University in Toruń, Lwowska 1, 87-100 Toruń, Poland; Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University in Toruń, Wileńska 4, 87-100 Toruń, Poland
| | - Jacek Kęsy
- Plant Physiology and Biotechnology Department, Nicolaus Copernicus University in Toruń, Lwowska 1, 87-100 Toruń, Poland
| | - Natalia Mucha
- Plant Physiology and Biotechnology Department, Nicolaus Copernicus University in Toruń, Lwowska 1, 87-100 Toruń, Poland
| | - Jarosław Tyburski
- Plant Physiology and Biotechnology Department, Nicolaus Copernicus University in Toruń, Lwowska 1, 87-100 Toruń, Poland; Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University in Toruń, Wileńska 4, 87-100 Toruń, Poland.
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Drew D, Boudker O. Ion and lipid orchestration of secondary active transport. Nature 2024; 626:963-974. [PMID: 38418916 DOI: 10.1038/s41586-024-07062-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 01/12/2024] [Indexed: 03/02/2024]
Abstract
Transporting small molecules across cell membranes is an essential process in cell physiology. Many structurally diverse, secondary active transporters harness transmembrane electrochemical gradients of ions to power the uptake or efflux of nutrients, signalling molecules, drugs and other ions across cell membranes. Transporters reside in lipid bilayers on the interface between two aqueous compartments, where they are energized and regulated by symported, antiported and allosteric ions on both sides of the membrane and the membrane bilayer itself. Here we outline the mechanisms by which transporters couple ion and solute fluxes and discuss how structural and mechanistic variations enable them to meet specific physiological needs and adapt to environmental conditions. We then consider how general bilayer properties and specific lipid binding modulate transporter activity. Together, ion gradients and lipid properties ensure the effective transport, regulation and distribution of small molecules across cell membranes.
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Affiliation(s)
- David Drew
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, Weill Cornell Medicine, New York, NY, USA.
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Babalola OO, Adedayo AA. Endosphere microbial communities and plant nutrient acquisition toward sustainable agriculture. Emerg Top Life Sci 2023; 7:207-217. [PMID: 37975608 PMCID: PMC10754323 DOI: 10.1042/etls20230069] [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: 07/08/2023] [Revised: 10/18/2023] [Accepted: 10/18/2023] [Indexed: 11/19/2023]
Abstract
Endophytic microbial communities have essential information for scientists based on their biological contribution to agricultural practices. In the external plant environment, biotic and abiotic factors affect microbial populations before getting into plant tissues. Endophytes are involved in mutualistic and antagonistic activities with the host plant. Microbial communities inhabiting the internal tissues of plant roots depend on their ability to live and contend with other plant microflora. The advantageous ones contribute to soil health and plant growth either directly or indirectly. The microbial communities move via soil-root environment into the endosphere of plants promoting plant growth features like antibiosis, induced systemic resistance, phytohormone synthesis, and bioremediation. Therefore, the existence of these microorganisms contributes to plant genomes, nutrient availability in the soil, the presence of pathogens, and abiotic factors. This review aims at how endophytic microorganisms have displayed great interest in contributing to abundant crop production and phytopathogen inhibition.
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Affiliation(s)
- Olubukola Oluranti Babalola
- Food Security and Safety Focus Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Mail Bag 2046, Mmabatho, South Africa
| | - Afeez Adesina Adedayo
- Food Security and Safety Focus Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Mail Bag 2046, Mmabatho, South Africa
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Ung KL, Schulz L, Kleine-Vehn J, Pedersen BP, Hammes UZ. Auxin transport at the endoplasmic reticulum: roles and structural similarity of PIN-FORMED and PIN-LIKES. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:6893-6903. [PMID: 37279330 DOI: 10.1093/jxb/erad192] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 06/02/2023] [Indexed: 06/08/2023]
Abstract
Auxin is a crucial plant hormone that controls a multitude of developmental processes. The directional movement of auxin between cells is largely facilitated by canonical PIN-FORMED proteins in the plasma membrane. In contrast, non-canonical PIN-FORMED proteins and PIN-LIKES proteins appear to reside mainly in the endoplasmic reticulum. Despite recent progress in identifying the roles of the endoplasmic reticulum in cellular auxin responses, the transport dynamics of auxin at the endoplasmic reticulum are not well understood. PIN-LIKES are structurally related to PIN-FORMED proteins, and recently published structures of these transporters have provided new insights into PIN-FORMED proteins and PIN-LIKES function. In this review, we summarize current knowledge on PIN-FORMED proteins and PIN-LIKES in intracellular auxin transport. We discuss the physiological properties of the endoplasmic reticulum and the consequences for transport processes across the ER membrane. Finally, we highlight the emerging role of the endoplasmic reticulum in the dynamics of cellular auxin signalling and its impact on plant development.
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Affiliation(s)
- Kien Lam Ung
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
| | - Lukas Schulz
- Plant Systems Biology, School of Life Sciences Weihenstephan, Technical University of Munich, 85354 Freising, Germany
| | - Jürgen Kleine-Vehn
- Institute of Biology II, Department of Molecular Plant Physiology (MoPP), University of Freiburg, 79104 Freiburg, Germany
- Center for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, 79104 Freiburg, Germany
| | | | - Ulrich Z Hammes
- Plant Systems Biology, School of Life Sciences Weihenstephan, Technical University of Munich, 85354 Freising, Germany
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Ung KL, Schulz L, Stokes DL, Hammes UZ, Pedersen BP. Substrate recognition and transport mechanism of the PIN-FORMED auxin exporters. Trends Biochem Sci 2023; 48:937-948. [PMID: 37574372 PMCID: PMC10592131 DOI: 10.1016/j.tibs.2023.07.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 06/30/2023] [Accepted: 07/17/2023] [Indexed: 08/15/2023]
Abstract
Auxins are pivotal plant hormones that regulate plant growth and transmembrane polar auxin transport (PAT) direct patterns of development. The PIN-FORMED (PIN) family of membrane transporters mediate auxin export from the plant cell and play crucial roles in PAT. Here we describe the recently solved structures of PIN transporters, PIN1, PIN3, and PIN8, and also their mechanisms of substrate recognition and transport of auxin. We compare structures of PINs in both inward- and outward-facing conformations, as well as PINs with different binding configurations for auxin. By this comparative analysis, a model emerges for an elevator transport mechanism. Central structural elements necessary for function are identified, and we show that these are shared with other distantly related protein families.
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Affiliation(s)
- Kien Lam Ung
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
| | - Lukas Schulz
- Plant Systems Biology, School of Life Sciences Weihenstephan, Technical University of Munich, 85354 Freising, Germany
| | - David L Stokes
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, NY 10016, USA
| | - Ulrich Z Hammes
- Plant Systems Biology, School of Life Sciences Weihenstephan, Technical University of Munich, 85354 Freising, Germany
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Joshi C, Napier R. PIN structures shed light on their mechanism of auxin efflux. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:4377-4383. [PMID: 37195878 PMCID: PMC10433929 DOI: 10.1093/jxb/erad185] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 05/16/2023] [Indexed: 05/19/2023]
Abstract
Polar auxin transport is a quintessential feature of higher plant physiology and it has been known for many years that some of the primary drivers of polar auxin transport are the PIN-formed (PIN) auxin efflux proteins. Formative research established many key biochemical features of the transport system and discovered inhibitors such as 1-naphthylphthalamic acid (NPA), but the mechanism of action of PINs has remained elusive. This changed in 2022 with the publication of high-resolution structures of the membrane-spanning domains of three PIN proteins. The atomic structures and associated activity assays reveal that PINs use an elevator mechanism to transport auxin anions out of the cell. NPA was shown to be a competitive inhibitor that traps PINs in their inward-open conformation. The secrets of the hydrophilic cytoplasmic loop of PIN proteins remain to be discovered.
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Affiliation(s)
- Chitra Joshi
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Richard Napier
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
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Bavnhøj L, Driller JH, Zuzic L, Stange AD, Schiøtt B, Pedersen BP. Structure and sucrose binding mechanism of the plant SUC1 sucrose transporter. NATURE PLANTS 2023; 9:938-950. [PMID: 37188854 PMCID: PMC10281868 DOI: 10.1038/s41477-023-01421-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 04/19/2023] [Indexed: 05/17/2023]
Abstract
Sucrose import from photosynthetic tissues into the phloem is mediated by transporters from the low-affinity sucrose transporter family (SUC/SUT family). Furthermore, sucrose redistribution to other tissues is driven by phloem sap movement, the product of high turgor pressure created by this import activity. Additionally, sink organs such as fruits, cereals and seeds that accumulate high concentrations of sugar also depend on this active transport of sucrose. Here we present the structure of the sucrose-proton symporter, Arabidopsis thaliana SUC1, in an outward open conformation at 2.7 Å resolution, together with molecular dynamics simulations and biochemical characterization. We identify the key acidic residue required for proton-driven sucrose uptake and describe how protonation and sucrose binding are strongly coupled. Sucrose binding is a two-step process, with initial recognition mediated by the glucosyl moiety binding directly to the key acidic residue in a stringent pH-dependent manner. Our results explain how low-affinity sucrose transport is achieved in plants, and pinpoint a range of SUC binders that help define selectivity. Our data demonstrate a new mode for proton-driven symport with links to cation-driven symport and provide a broad model for general low-affinity transport in highly enriched substrate environments.
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Affiliation(s)
- Laust Bavnhøj
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Jan Heiner Driller
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Lorena Zuzic
- Department of Chemistry, Aarhus University, Aarhus, Denmark
| | | | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Aarhus, Denmark
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