Pea G-protein γ subunits: Unlocking their potential in physiological stress and mycorrhizal mediated nutrient sensing

Heterotrimeric GTP-binding proteins or G-proteins are pivotal players in the intricate signaling cascades of plant cells, operating through their binding to guanine nucleotides. These G-proteins primarily consist of three essential subunits: Gα, Gβ, and Gγ. Among these subunits, Gγ stands out for its remarkable genetic diversity. In the present investigation, six Gγ subunits were identified in the Indian variety T-163 of the pea plant (Pisum sativum). Notably, two of these novel Gγ subunits, named PsGγ1 and PsGγ2, belong to type A, while PsGγ3 falls within the type B category. The remaining three subunits, namely PsGγ4, PsGγ5, and PsGγ6, are classified under type C. An in-depth comparison of the amino acid sequences of these pea Gγ subunits with their counterparts in other plants, including Arabidopsis thaliana and Oryza sativa, has unveiled significant variations. This research explores the impact of different treatments on PsGγ genes (PsGγ1 to PsGγ6) in plants. Noteworthy discoveries include a 4-fold increase in the expression of PsGγ1, PsGγ4, PsGγ5, and PsGγ6 in the presence of nitrogen. PsGγ2 and PsGγ3, however, show no response. Phosphorus induces a 3-fold upregulation in PsGγ2 and PsGγ4, and a 4-fold increase in PsGγ5. Conversely, the absence of phosphorus triggers a 4-fold upregulation in PsGγ4 and PsGγ5. Heat stress leads to a 3-fold upregulation in PsGγ2, PsGγ4, and PsGγ5, while cold stress results in a 3-fold upregulation of PsGγ1 and PsGγ6. Under high salt conditions, PsGγ1, PsGγ3, PsGγ4, and PsGγ6 exhibit a 4-fold upregulation, with PsGγ2 showing a 2-fold increase. PsGγ4 and PsGγ5 display a 4-fold upregulation in response to ABA, while PsGγ2 and PsGγ3 show a 3-fold increase while MeJA induces a 4-fold upregulation in PsGγ5. Notably, this study unveils, for the first time, the significant role of Gγ subunits during endosymbiotic associations with phosphorus-acquiring AMF with AMF triggering a 4-fold upregulation in PsGγ4 and PsGγ6. The presence of multiple Gγ subunits in pea underscores their critical participation in governing plant development, stress responses, nutrient sensing, and interactions with mycorrhizal fungi.