4 research outputs found
Recommended from our members
ColeRexBotanyPlantPathologyDevelopmentallyDistinctActivities_AdditionalFiles.zip
BACKGROUND: Exocytosis is integral to root growth: trafficking components of systems that control growth (e.g., PIN
auxin transport proteins) to the plasma membrane, and secreting materials that expand the cell wall to the
apoplast. Spatiotemporal regulation of exocytosis in eukaryotes often involves the exocyst, an octameric complex
that tethers selected secretory vesicles to specific sites on the plasma membrane and facilitates their exocytosis. We
evaluated Arabidopsis lines with mutations in four exocyst components (SEC5, SEC8, EXO70A1 and EXO84B) to
explore exocyst function in primary root growth.
RESULTS: The mutants have root growth rates that are 82% to 11% of wild-type. Even in lines with the most severe
defects, the organization of the quiescent center and tissue layers at the root tips appears similar to wild-type, although
meristematic, transition, and elongation zones are shorter. Reduced cell production rates in the mutants are due to the
shorter meristems, but not to lengthened cell cycles. Additionally, mutants demonstrate reduced anisotropic cell
expansion in the elongation zone, but not the meristematic zone, resulting in shorter mature cells that are similar in
shape to wild-type. As expected, hypersensitivity to brefeldin A links the mutant root growth defect to altered vesicular
trafficking. Several experimental approaches (e.g., dose–response measurements, localization of signaling components)
failed to identify aberrant auxin or brassinosteroid signaling as a primary driver for reduced root growth in exocyst
mutants.
CONCLUSIONS: The exocyst participates in two spatially distinct developmental processes, apparently by mechanisms
not directly linked to auxin or brassinosteroid signaling pathways, to help establish root meristem size, and to facilitate
rapid cell expansion in the elongation zone.Keywords: Cell expansion, Brassinosteroid, Auxin, Exocyst, Root growth, MeristemKeywords: Cell expansion, Brassinosteroid, Auxin, Exocyst, Root growth, Meriste