Function of membrane domains in rho-of-plant signaling

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 nano-scale organization of ROPs in membranes could determine signaling parameters like signal specificity, amplification and integration.

Arabidopsis pavement cell shape formation involves spatially confined ROPGAP regulators

“…Major protagonists of cell polarity signaling in plants are the small GTPases of the Rho-related GTPases of plants (ROPs) subfamily, distantly related to Rho/Rac small GTPases in opistokonts. [3][4][5][6] Similar to their animal and yeast counterparts, ROPs are molecular switches, cycling between an inactive guanosine diphosphate (GDP)-bound form and an active guanosine triphosphate (GTP)bound form. [7][8][9] Via specific effector proteins, ROP signaling targets the cytoskeleton and cellular trafficking pathways, thereby contributing to cell wall remodeling in response to stimuli of various origin.…”

Barley guanine nucleotide exchange factorHvGEF14 is an activator of the susceptibility factorHvRACB and supports host cell entry byBlumeria graminisf.sp.hordei

“…Alternatively, activated ROPs might stay in contact to GEFs for a feedback regulation on ROP activity through complexes formed with ROP executers as discussed before (Wu and Lew, 2013). Because PRONE-GEFs including HvGEF14 can form dimers, GEF-GEF -ROP-GTP interaction could also recruit further ROP-GDP for activation (Smokvarska et al, 2021).…”

Imaging the living plant cell: From probes to quantification

“…Several techniques have been used to visualize nanodomains in the living plant plasma membrane and to probe their dynamics, notably Total Internal Resonance Fluorescence Microscopy (TIRFM), PhotoActivated Localization Microscopy (PALM), and Single Particle Tracking (SPT) techniques (Table 1) (Martiniere et al, 2012;Hosy et al, 2015;Gronnier et al, 2017;Wang et al, 2018;Martiniere et al, 2019;Platre et al, 2019;Zhang et al, 2019;Smokvarska et al, 2020;Bayle et al, 2021;Noack et al, 2021). These methods have revealed a number of nanodomain-resident proteins, such a Remorins, Flotilins, HYPERSENSITIVE INDUCED REACTION proteins (HIRs), and receptor-like kinases (Li et al, 2012;Bucherl et al, 2017;Daněk et al, 2020;Gronnier et al, 2020;Jaillais and Ott, 2020;Gouguet et al, 2021;Martinière and Zelazny, 2021), as well as some proteins with a dynamic association with nanodomains, such as small GTPases from the RHO-OF-PLANTs (ROP) family (Platre et al, 2019;Smokvarska et al, 2020;Bayle et al, 2021;Fuchs et al, 2021;Smokvarska et al, 2021).…”