Pea Gβ subunit of G proteins has a role in nitric oxide-induced stomatal closure in response to heat and drought stress

Heterotrimeric G proteins consisting of G alpha, G beta and G gamma subunits act as downstream effectors to regulate multiple functions including abiotic stress tolerance. However, the mechanism of G beta-mediated heat and drought tolerance is yet to be established. To explore the role ofPisum sativumG beta subunit (PsG beta) in heat and drought stress, transgenic tobacco plants overexpressing (OEs) PsG beta were raised. Transgenic plants showing ectopic expression of PsG beta performed better under heat and drought stress in comparison with vector control plants. The seed germination, relative water content (RWC) and nitric oxide (NO) induction in the guard cells of transgenic plants were significantly higher in contrast to control plants. PsG beta promoter was isolated and several stress-responsive elements were identified. The change in G beta expression in response to heat, methyl jasmonate (MeJA), abscisic acid (ABA), drought and salt confirms the presence of heat, low temperature and drought-responsive elements in the PsG beta promoter. Also, heat and drought stress caused the release of NO-induced stomatal closure in the leaves of transgenic tobacco plants OEs PsG beta. The better performance of transgenic plant OEs PsG beta is also attributed to the improved photosynthetic parameters as compared with control plants. These findings suggest a role of PsG beta in the signalling pathway leading to NO-induced stomatal closure during heat and drought stress.