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.
Donald Danforth Plant Science Center, St. Louis, MO 63132, USA.
Mary L
ML
Preuss
Aaron J
AJ
Schmitz
Julie M
JM
Thole
Heather K S
HK
Bonner
Marisa S
MS
Otegui
Erik
E
Nielsen
D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D049108:Cell Enlargement / Q000187:drug effects; D016764:Cell Polarity / Q000502:physiology; D007476:Ionophores / Q000494:pharmacology; D008854:Microscopy, Electron; D009154:Mutation; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D011485:Protein Binding; D020798:Two-Hybrid System Techniques; D020695:rab4 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D021601:trans-Golgi Network / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure
D029681:Arabidopsis Proteins; C417306:CBL protein, Arabidopsis; D002135:Calcium-Binding Proteins; D007476:Ionophores; D000001:Calcimycin; D019870:1-Phosphatidylinositol 4-Kinase; D020695:rab4 GTP-Binding Proteins