Function of membrane domains in rho-of-plant signaling.

Yvon Jaillais,Alexandre Martinière,Marija Smokvarska

doi:10.1093/plphys/kiaa082

Abstract

In a crowded environment, establishing interactions between different molecular partners can take a long time. Biological membranes have solved this issue, as they simultaneously are fluid and possess compartmentalized domains. This nanoscale organization of the membrane is often based on weak, local, and multivalent interactions between lipids and proteins. However, from local interactions at the nanoscale, different functional properties emerge at the higher scale, and these are critical to regulate and integrate cellular signaling. Rho of Plant (ROP) proteins are small guanosine triphosphate hydrolase enzymes (GTPases) involved in hormonal, biotic, and abiotic signaling, as well as fundamental cell biological properties such as polarity, vesicular trafficking, and cytoskeleton dynamics. Association with the membrane is essential for ROP function, as well as their precise targeting within micrometer-sized polar domains (i.e. microdomains) and nanometer-sized clusters (i.e. nanodomains). Here, we review our current knowledge about the formation and the maintenance of the ROP domains in membranes. Furthermore, we propose a model for ROP membrane targeting and discuss how the nanoscale organization of ROPs in membranes could determine signaling parameters like signal specificity, amplification, and integration.

Highlights

Rho of Plant (ROP) proteins are members of the small guanosine triphosphate hydrolase enzymes (GTPases) family that are about 20 kDa, essentially made of their GTPase domain with short N- and Cterminal extensions (Figure 1A)
A ROP63Q mutant, which has six-net remaining positive charges, shows an intermediate localization, with increased plasma membrane targeting compared to ROP67Q, but which is still present in intracellular compartments, in contrast to wild-type ROP6 (Figure 4A) (Platre et al, 2019)
A substantial number of publications have revealed the formation of large domains in the plant plasma membrane, including at the site for root hair initiation, in the tip of pollen tube or in metaxylem cells (Figure 2)

Summary

Introduction

Rho of Plant (ROP) proteins are members of the small GTPase family that are about 20 kDa, essentially made of their GTPase domain ( called a G domain) with short N- and Cterminal extensions (Figure 1A). In contrast to the multiple cell wall pits of the metaxylem, the positioning and establishment of a single polar root hair at a stereotypical position within the trichoblast plasma membrane is likely to require a mechanism that eliminates randomness during its formation.

Results

Conclusion