Journal
JOURNAL OF CELL BIOLOGY
Volume 172, Issue 7, Pages 991-998Publisher
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.200508116
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The RabA4b GTPase labels a novel, trans-Golgi network compartment displaying a developmentally regulated polar distribution in growing Arabidopsis thaliana root hair cells. GTP bound RabA4b selectively recruits the plant phosphatidylinositol 4-OH kinase, PI-4K beta 1, but not members of other PI-4K families. PI-4K beta 1 colocalizes with RabA4b on tip-localized membranes in growing root hairs, and mutant plants in which both the PI-4K beta 1 and -4K beta 2 genes are disrupted display aberrant root hair morphologies. PI-4K beta 1 interacts with RabA4b through a novel homology domain, specific to eukaryotic type III beta PI-4Ks, and PI-4K beta 1 also interacts with a Ca2+ sensor, AtCBL1, through its NH2 terminus. We propose that RabA4b recruitment of PI-4K beta 1 results in Ca2+-dependent generation of PI-4P on this compartment, providing a link between Ca2+ and PI-4,5P(2)-dependent signals during the polarized secretion of cell wall components in tip-growing root hair cells.
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