New insights into Rho signaling from plant ROP/Rac GTPases

Abstract

In animal and plant cells, a wide range of key cellular processes that require the establishment of cell polarity are governed by Rho-GTPases. In contrast to animals and yeast, however, plants possess a single Rho-GTPase subfamily called ROP (Rho-like GTPases from plants). This raises the question of how plants achieve the high level of regulation required for polar cellular processes. It is becoming evident that plants have evolved specific regulators, including ROP-Guanine Exchange Factors (GEFs) and the Rop-interactive CRIB motif–containing proteins (RIC) effectors. Recent research shows that the spatiotemporal dynamics of ROPs, the cytoskeleton, endocytosis and exocytosis are intertwined. This review focuses on the proposed self-organizing nature of ROPs in plants and how ROP-mediated cellular mechanisms compare with those responsible for cell polarity in animals and yeast.

The Small GTPase ROP10 of Medicago truncatula Is Required for Both Tip Growth of Root Hairs and Nod Factor-Induced Root Hair Deformation

“…These small GTPases act as molecular switches by cycling between a GDPbound inactive form and a GTP-bound active form. The membraneassociated activated GTP-bound forms interact with cellular effectors, which in turn trigger multiple extracellular signal-induced downstream responses such as leaf cell morphogenesis, polarized cell growth, pathogen defense reactions, abiotic stress-related responses, and plant hormone responses (Nibau et al, 2006;Craddock et al, 2012).…”

Novel ABP1-TMK auxin sensing system controls ROP GTPase-mediated interdigitated cell expansion in Arabidopsis

“…[15][16][17] On the cell surface of the PCs, ABP1-based auxin signal rapidly activates both ROP2 and ROP6 pathways for local intra-and inter-cellular coordination of interdigitating lobes and indentations.…”

“…This leads to a speculation that RLKs could be a primary mechanism by which extracellular signals activate ROPs in plants. 17,39 Having a RLK cell surface receptor like the TMKs family to perceive a ROP activating signal from adjacent cells could be a common mechanism for cell-cell coordination for the spatial control of cellular processes in multicellular plant tissues consisting of walled cells. Therefore further identifying specific RopGEFs regulated by different TMKs will be a fertile field for future studies of ROP signaling in connection to developmental mechanisms in plants.…”

In vivomonitoring of plant small GTPase activation using a Förster resonance energy transfer biosensor

“…Rac/ROP family small GTPases are master regulators, controlling various signalling systems in plants such as those governing pollen tube growth, root hair development, auxin signaling, and disease resistance (13)(14)(15)(16). Therefore, monitoring the activation state of a Rac/ROP GTPase within living cells is critical to further understanding its functions.…”