ROP (Rho-Related Protein from Plants) GTPases for Spatial Control of Root Hair Morphogenesis
Cell polarity control is inherently a complex process based on the feedback loops where it is difficult to distinguish cause–effect relationships and identify “master regulators.” However, small GTPases from the Rac/Rho family are certainly an important part of polar growth core regulatory circuit/network also in plants. ROPs (Rac/Rho of plant) involvement in root hair polar tip-growth is best documented by the loss of polarity in plants overexpressing specific ROP GTPases, loss of polarized cell expansion in root hairs of RopGDI mutant and root hair tip localization of ROP-GFP fusions. Rho/Rac GTPases switch directs cell growth via a plethora of regulatory and effector proteins known from Opisthokonts, and only recently some of them have been identified also in plant cells. We will review and discuss their root hair function in relation to the cytoskeleton dynamics, Ca2+ gradient, NADPH oxidase activity/ROS (reactive oxygen species), cell wall dynamics, phospholipid signaling, auxin signaling, and polarized/targeted secretory vesicle transport and fusion.
KeywordsPollen Tube Root Hair Phosphatidic Acid Root Hair Development Membrane Recycling
Acknowledgments We are grateful to Hana Soukupova for the help with the finalization of this chapter. The related work in the author’s laboratories was supported by the Academy of Sciences of the Czech Republic Grant Agency grant IAA6038410 to V.Z., NSF grant IBN-0420226 to J.F., and KONTAKT MSMT CR – ME841 and MSM0021620858 to V.Z.
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