title: The GRV2/RME-8 protein of Arabidopsis functions in the late endocytic pathway and is required for vacuolar membrane flow.
abstract: The gravitropism defective 2 (grv2) mutants of Arabidopsis thaliana were previously characterized as exhibiting shoot agravitropism resulting from mutations in a homolog of the Caenorhabditis elegans RECEPTOR-MEDIATED ENDOCYTOSIS-8 (RME-8) gene, which is required in C. elegans for endocytosis. A fluorescent protein fusion to the GRV2 protein localized to endosomes in transgenic plants, and vacuolar morphology was altered in grv2 mutants. A defect in vacuolar membrane dynamics provides a mechanistic explanation for the gravitropic defect, and may also account for the presence of an enlarged vacuole in early embryos, together with a nutrient requirement during seedling establishment. The GRV2-positive endosomes were sensitive to Wortmannin but not brefeldin A (BFA), consistent with GRV2 operating late in the endocytic pathway, prior to delivery of vesicles to the central vacuole. The specific enlargement of GRV2:YFP structures by Wortmannin, together with biochemical data showing that GRV2 co-fractionates with pre-vacuolar markers such as PEP12/SYP21, leads us to conclude that in plants GRV2/RME-8 functions in vesicle trafficking from the multivesicular body/pre-vacuolar compartment to the lytic vacuole.
authors.affiliation: Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Silady
authors.forename: David W
authors.initials: DW
authors.lastname: Ehrhardt
authors.forename: Karen
authors.initials: K
authors.lastname: Jackson
authors.forename: Christine
authors.initials: C
authors.lastname: Faulkner
authors.forename: Karl
authors.initials: K
authors.lastname: Oparka
authors.forename: Chris R
authors.initials: CR
authors.lastname: Somerville
mesh_terms: D000730:Androstadienes / Q000493:pharmacokinetics / Q000494:pharmacology; D000818:Animals; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D017173:Caenorhabditis elegans / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018522:Gravitropism / Q000235:genetics / Q000502:physiology; D007425:Intracellular Membranes / Q000378:metabolism; D009154:Mutation; D014617:Vacuoles / Q000378:metabolism / Q000502:physiology; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D029681:Arabidopsis Proteins; D029721:Drosophila Proteins; C519878:KAM2 protein, Arabidopsis; C489292:Rme-8 protein, Drosophila; D033921:Vesicular Transport Proteins; D020126:Brefeldin A; D000077191:Wortmannin