Heterotrimeric G Protein–Coupled Signaling in Plants

Abstract

Investigators studying G protein–coupled signaling—often called the best-understood pathway in the world owing to intense research in medical fields—have adopted plants as a new model to explore the plasticity and evolution of G signaling. Much research on plant G signaling has not disappointed. Although plant cells have most of the core elements found in animal G signaling, differences in network architecture and intrinsic properties of plant G protein elements make G signaling in plant cells distinct from the animal paradigm. In contrast to animal G proteins, plant G proteins are self-activating, and therefore regulation of G activation in plants occurs at the deactivation step. The self-activating property also means that plant G proteins do not need and therefore do not have typical animal G protein–coupled receptors. Targets of activated plant G proteins, also known as effectors, are unlike effectors in animal cells. The simpler repertoire of G signal elements in Arabidopsis makes G signaling easier to manipulate in a multicellular context.

Phosphorylation-Dependent Regulation of G-Protein Cycle during Nodule Formation in Soybean

“…The simplicity of G-protein complex system in Arabidopsis, together with the ease of performing direct genetic analysis of loss-of-function mutants, has enabled the identification of a multitude of processes that involve G-proteins. Phenotypic analysis combined with large-scale transcriptomic analyses have also identified several modes of G-protein function, some similar to what exists in other systems and others specific to plants (Pandey et al, 2010;Urano and Jones, 2014). Rate of Pi release due to the GTPase activity of Ga1 in the presence of varying concentrations of native and mutant RGS2 proteins.…”

“…RGS proteins are central to the regulation of the G-protein cycle, especially in plants ( Urano and Jones, 2014). It has been proposed that GTP hydrolysis by Ga protein is the rate-limiting step of the G-protein cycle in plants, in contrast to mammalian systems, where GDP to GTP exchange is the rate-limiting step (Johnston et al, 2007).…”

On plant defense signaling networks and early land plant evolution

“…Components of the heterotrimeric G-protein complex, a signaling switch that consists of an α-, β- and several γ-subunits [76], are involved in land plant defense responses (e.g. [77],); the role of β- and γ-subunits in defense is also implicated to be mediated by FLS2, EF-Tu and CERK1 in A. thaliana [78].…”

Phospholipases as GTPase activity accelerating proteins (GAPs) in plants

“…[1][2][3] The core of the heterotrimeric protein consists of a complex made of one Ga, one Gb and one Gg protein. The Ga protein acts as a bimodal molecular switch controlling the 'on' or 'off' stages of signaling (Fig.…”

“…11,12 Therefore, it was surprising that many plant species, especially those of the monocot lineage, do not have an obvious RGS homolog in their genomes. 1 The commonly studied monocots such as rice, maize, sorghum and Brachypodium possess the complete repertoire of G-proteins, but no RGS protein. This apparent discrepancy can be explained in 2 possible ways; one the G-protein cycle in plants with no RGS is regulated differently from the ones that have RGS protein i. e., the Ga proteins from plants without RGS proteins exhibit significantly faster inherent rates of GTP hydrolysis.…”