A role for the RabA4b effector protein PI-4Kbeta1 in polarized expansion of root hair cells in Arabidopsis thaliana.

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-4Kbeta1, but not members of other PI-4K families. PI-4Kbeta1 colocalizes with RabA4b on tip-localized membranes in growing root ...
hairs, and mutant plants in which both the PI-4Kbeta1 and -4Kbeta2 genes are disrupted display aberrant root hair morphologies. PI-4Kbeta1 interacts with RabA4b through a novel homology domain, specific to eukaryotic type IIIbeta PI-4Ks, and PI-4Kbeta1 also interacts with a Ca2+ sensor, AtCBL1, through its NH2 terminus. We propose that RabA4b recruitment of PI-4Kbeta1 results in Ca2+-dependent generation of PI-4P on this compartment, providing a link between Ca2+ and PI-4,5P2-dependent signals during the polarized secretion of cell wall components in tip-growing root hair cells.
Mesh Terms:
1-Phosphatidylinositol 4-Kinase, Arabidopsis, Arabidopsis Proteins, Binding Sites, Biological Transport, Calcimycin, Calcium-Binding Proteins, Cell Enlargement, Cell Polarity, Ionophores, Microscopy, Electron, Mutation, Plant Roots, Protein Binding, Two-Hybrid System Techniques, rab4 GTP-Binding Proteins, trans-Golgi Network
J. Cell Biol.
Date: Mar. 27, 2006
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