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  • 1
    Language: English
    In: eLife, 2014-04-08, Vol.3, p.e02131-e02131
    Description: Membrane trafficking is essential to fundamental processes in eukaryotic life, including cell growth and division. In plant cytokinesis, post-Golgi trafficking mediates a massive flow of vesicles that form the partitioning membrane but its regulation remains poorly understood. Here, we identify functionally redundant Arabidopsis ARF guanine-nucleotide exchange factors (ARF-GEFs) BIG1-BIG4 as regulators of post-Golgi trafficking, mediating late secretion from the trans-Golgi network but not recycling of endocytosed proteins to the plasma membrane, although the TGN also functions as an early endosome in plants. In contrast, BIG1-4 are absolutely required for trafficking of both endocytosed and newly synthesized proteins to the cell-division plane during cytokinesis, counteracting recycling to the plasma membrane. This change from recycling to secretory trafficking pathway mediated by ARF-GEFs confers specificity of cargo delivery to the division plane and might thus ensure that the partitioning membrane is completed on time in the absence of a cytokinesis-interphase checkpoint. DOI: http://dx.doi.org/10.7554/eLife.02131.001.
    Subject(s): Arabidopsis Proteins - metabolism ; Endocytosis ; Cell Division ; Golgi Apparatus - metabolism ; Arabidopsis Proteins - secretion ; Arabidopsis - metabolism ; Protein Transport ; Seeds ; Cytokinesis ; Guanine ; Golgi apparatus ; Proteins ; Microscopy ; Phylogenetics ; Membrane trafficking ; Physiology ; Software ; Flowers & plants ; Recycling ; Molecular biology ; Guanine nucleotide exchange factor ; Localization ; Index Medicus ; Plant Biology ; ARF-GEF ; secretion ; Arabidopsis ; cell division ; post-Golgi trafficking ; recycling ; gegulation of vesicle traffic ; Cell Biology
    ISSN: 2050-084X
    E-ISSN: 2050-084X
    Source: PubMed Central
    Source: Directory of Open Access Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 2
    Language: English
    In: The New phytologist, 2021-01, Vol.229 (2), p.979-993
    Description: Summary Cytokinin and auxin are key regulators of plant growth and development. During the last decade transport mechanisms have turned out to be the key for the control of local and long‐distance hormone distributions. In contrast with auxin, cytokinin transport is poorly understood. Here, we show that Arabidopsis thaliana AZG2, a member of the AZG purine transporter family, acts as cytokinin transporter involved in root system architecture determination. Even though purines are substrates for both AZG1 and AZG2, we found distinct transport mechanisms. The expression of AZG2 is restricted to a small group of cells surrounding the lateral root (LR) primordia and induced by auxins. Compared to the wild‐type (WT), mutants carrying loss‐of‐function alleles of AZG2 have higher LR density, suggesting that AZG2 is part of a regulatory pathway in LR emergence. Moreover, azg2 is partially insensitive to exogenous cytokinin, which is consistent with the observation that the cytokinin reporter TCSnpro:GFP showed lower fluorescence signal in the roots of azg2 compared to the WT. These results indicate a defective cytokinin signalling pathway in the region of LR primordia. The integration of AZG2 subcellular localization and cytokinin transport capacity data allowed us to propose a local cytokinin : auxin signalling model for the regulation of LR emergence.
    Subject(s): cytokinin transport ; development ; auxin ; lateral root primordia ; lateral root ; lateral root overlying tissues ; AZG ; phytohormone ; Arabidopsis thaliana ; Cytokinins ; Auxin ; Analysis ; Index Medicus
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 3
    Language: English
    In: Current biology, 2014, Vol.24 (12), p.1383-1389
    Description: Plasma-membrane proteins such as ligand-binding receptor kinases, ion channels, or nutrient transporters are turned over by targeting to a lytic compartment--lysosome or vacuole--for degradation. After their internalization, these proteins arrive at an early endosome, which then matures into a late endosome with intraluminal vesicles (multivesicular body, MVB) before fusing with the lysosome/vacuole in animals or yeast. The endosomal maturation step involves a SAND family protein mediating Rab5-to-Rab7 GTPase conversion. Vacuolar trafficking is much less well understood in plants. Here we analyze the role of the single-copy SAND gene of Arabidopsis. In contrast to its animal or yeast counterpart, Arabidopsis SAND protein is not required for early-to-late endosomal maturation, although its role in mediating Rab5-to-Rab7 conversion is conserved. Instead, Arabidopsis SAND protein is essential for the subsequent fusion of MVBs with the vacuole. The inability of sand mutant to mediate MVB-vacuole fusion is not caused by the continued Rab5 activity but rather reflects the failure to activate Rab7. In conclusion, regarding the endosomal passage of cargo proteins for degradation, a major difference between plants and nonplant organisms might result from the relative timing of endosomal maturation and SAND-dependent Rab GTPase conversion as a prerequisite for the fusion of late endosomes/MVBs with the lysosome/vacuole.
    Subject(s): rab GTP-Binding Proteins - metabolism ; Arabidopsis Proteins - genetics ; Arabidopsis - enzymology ; Nuclear Proteins - metabolism ; rab GTP-Binding Proteins - genetics ; Endosomes - metabolism ; Arabidopsis - metabolism ; Protein Transport ; Arabidopsis - genetics ; Arabidopsis Proteins - metabolism ; Lysosomes - metabolism ; Gene Expression Regulation, Plant ; Vacuoles - metabolism ; Multivesicular Bodies - metabolism ; Nuclear Proteins - genetics ; Arabidopsis thaliana ; Plant physiology ; Analysis ; Physiological aspects ; Molecular biology ; Phosphotransferases ; Membrane proteins ; Protein binding ; Index Medicus
    ISSN: 0960-9822
    E-ISSN: 1879-0445
    Source: Backfile Package - All of Back Files EBS [ALLOFBCKF]
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 4
    Language: English
    In: The Plant cell, 2020-08, Vol.32 (8), p.2491-2507
    Description: Membrane trafficking maintains the organization of the eukaryotic cell and delivers cargo proteins to their subcellular destinations, such as sites of action or degradation. The formation of membrane vesicles requires the activation of the ADP-ribosylation factor ARF GTPase by the SEC7 domain of ARF guanine-nucleotide exchange factors (ARF-GEFs), resulting in the recruitment of coat proteins by GTP-bound ARFs. In vitro exchange assays were done with monomeric proteins, although ARF-GEFs form dimers in vivo. This feature is conserved across eukaryotes, although its biological significance is unknown. Here, we demonstrate the proximity of ARF1•GTPs in vivo by fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy, mediated through coordinated activation by dimers of Arabidopsis ( ) ARF-GEF GNOM, which is involved in polar recycling of the auxin transporter PIN-FORMED1. Mutational disruption of ARF1 spacing interfered with ARF1-dependent trafficking but not with coat protein recruitment. A mutation impairing the interaction of one of the two SEC7 domains of the GNOM ARF-GEF dimer with its ARF1 substrate reduced the efficiency of coordinated ARF1 activation. Our results suggest a model of coordinated activation-dependent membrane insertion of ARF1•GTP molecules required for coated membrane vesicle formation. Considering the evolutionary conservation of ARFs and ARF-GEFs, this initial regulatory step of membrane trafficking might well occur in eukaryotes in general.
    Subject(s): Arabidopsis Proteins - metabolism ; DNA-Binding Proteins - metabolism ; Transcription Factors - metabolism ; Phenotype ; Guanine Nucleotide Exchange Factors - metabolism ; Models, Biological ; Transport Vesicles - metabolism ; Plants, Genetically Modified ; Protein Multimerization ; Protein Binding ; Cell Membrane - metabolism ; Arabidopsis - metabolism ; Index Medicus
    ISSN: 1040-4651
    E-ISSN: 1532-298X
    Source: American Society of Plant Biologists
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 5
    Language: English
    In: The Plant cell, 2020-08-03, Vol.32 (8), p.2491
    Description: Membrane trafficking maintains the organization of the eukaryotic cell and delivers cargo proteins to their subcellular destinations, such as sites of action or degradation. The formation of membrane vesicles requires the activation of the ADP-ribosylation factor ARF GTPase by the SEC7 domain of ARF guanine-nucleotide exchange factors (ARF-GEFs), resulting in the recruitment of coat proteins by GTP-bound ARFs. In vitro exchange assays were done with monomeric proteins, although ARF-GEFs form dimers in vivo. This feature is conserved across eukaryotes, although its biological significance is unknown. Here, we demonstrate the proximity of ARF1•GTPs in vivo by fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy, mediated through coordinated activation by dimers of Arabidopsis (Arabidopsis thaliana) ARF-GEF GNOM, which is involved in polar recycling of the auxin transporter PIN-FORMED1. Mutational disruption of ARF1 spacing interfered with ARF1-dependent trafficking but not with coat protein recruitment. A mutation impairing the interaction of one of the two SEC7 domains of the GNOM ARF-GEF dimer with its ARF1 substrate reduced the efficiency of coordinated ARF1 activation. Our results suggest a model of coordinated activation-dependent membrane insertion of ARF1•GTP molecules required for coated membrane vesicle formation. Considering the evolutionary conservation of ARFs and ARF-GEFs, this initial regulatory step of membrane trafficking might well occur in eukaryotes in general.
    E-ISSN: 1532-298X
    Source: American Society of Plant Biologists
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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