A receptor-like kinase mediated phosphorylation of Gα protein affects signaling during nodulation

SO_SCPCAPUMMARYC_SCPCAPO_LIHeterotrimeric G-proteins, comprised of G, G{beta} and G{gamma} subunits regulate signaling in eukaryotes. In metazoans, G-proteins are activated by GPCR-mediated GDP to GTP exchange on G; however, the role of receptors in regulating plant G-protein signaling remains equivocal. Mounting evidence points to the involvement of receptor-like kinases (RLKs) in regulating plant G-protein signaling pathways, but their mechanistic details remain limited. We have previously shown that during soybean nodulation, the nod factor receptor 1 (NFR1) interacts with G-protein components and indirectly controls signaling. C_LIO_LIWe explored the direct regulation of G-protein signaling by RLKs using protein-protein interactions, receptor-mediated phosphorylation and the effects of such phosphorylations on soybean nodule formation. C_LIO_LIResults presented in this study demonstrate a direct, phosphorylation-based regulation of G by symbiosis receptor kinase (SymRK). SymRKs interact with and phosphorylate G at multiple residues, including two in its active site, which abolishes GTP binding. In addition, phospho-mimetic G fails to interact with G{beta}{gamma}, potentially allowing for constitutive signaling by the freed G{beta}{gamma}. C_LIO_LIThese results uncover a novel mechanism of G-protein cycle regulation in plants where receptor-mediated phosphorylation of G not only affects its activity, but also influences the availability of its signaling partners, thereby exerting a two-pronged control on signaling. C_LI