Spatial control of plasma membrane domains: ROP GTPase-based symmetry breaking

Abstract

Breaking of the cell membrane symmetry to form polarized or localized domains/regions of the plasma membrane (PM) is a fundamental cellular process that occurs in essentially all cellular organisms, and is required for a wide variety of cellular functions/behaviors including cell morphogenesis, cell division and cell differentiation. In plants, the development of localized or polarized PM domains has been linked to a vast array of cellular and developmental processes such as polar cell expansion, asymmetric cell division, cell morphogenesis, the polarization of auxin transporters (and thus auxin polar transport), secondary cell wall patterning, cell type specification, and tissue pattern formation. Rho GTPases from plants (ROPs) are known to be involved in many of these processes. Here, we review the current knowledge on ROP involvement in breaking symmetry and propose that ROP-based self-organizing signaling may provide a common mechanism for the spatial control of PM domains required in various cellular and developmental processes in plants.

RopGEF1 Plays a Critical Role in Polar Auxin Transport in Early Development

“…ROPs function as important regulators of hormone responses and PAT (Wu et al, 2011;Yang and Lavagi, 2012), and auxin is known to rapidly activate these small GTPases (Tao et al, 2002;Xu et al, 2010). As activators of ROPs, RopGEFs are inevitable links in auxinsignaled and ROP-mediated pathways, and they have been implicated in several auxin-regulated developmental processes (Chen et al, 2011;Duan et al, 2010).…”

“…ROPGTPases are important regulators of many biological processes including polar growth of pollen tubes and root hairs, hormone responses, PAT, and defense responses (Yalovsky et al, 2008;Wu et al, 2011;Yang and Lavagi, 2012). They function as molecular switches and cycle between GTP-bound active and GDP-bound inactive forms.…”

A Distinct Pathway for Polar Exocytosis in Plant Cell Wall Formation

“…Besides the roles of ROP1 in controlling pollen tube growth, recent studies suggest ROPs might also participate in other cell polarization processes (Yang and Lavagi, 2012). Cell plate formation in plant cells is assisted by the insertion of plant-specific polarized proteins/membrane to the forming sites (Bednarek and Falbel, 2002;Jurgens, 2005;Backues et al, 2007).…”

“…A constitutively active mutant of ROP1 (CA-rop1) prevents fusion of these vesicles with the PM and enhances the accumulation of exocytic vesicles in the apical cortex of pollen tubes (Lee et al, 2008). Although ROP GTPases have been extensively researched, their roles in polar membrane expansion in pollen tubes and epidermal pavement cells remains unclear Yang and Lavagi, 2012), and there have been insufficient studies on the functions of ROPs in controlling cell plate formation during cytokinesis. Cell division requires precise regulation and spatial organization of the cytoskeleton for delivery of secretion vesicles to the expanding cell plate (Molendijk et al, 2001).…”

Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes ofZea mays

“…In A. thaliana leaf epidermal cells, auxin that is transported in the apoplast, modulates the activity of ROP GTPases, which in turn influence AF-organization in neighbor cells. [50][51][52] Thus, RAC/ROPs (Rho-like Rac/Rop GTPases of plants) could function as spatial switches relaying localized auxin signals. 53 ROP patches follow auxin gradients that establish polarity in trichoblasts 53 and importantly, ROPs accumulate at the polar end of Z. mays SMCs.…”