G protein controls stress readiness by modulating transcriptional and metabolic homeostasis in Arabidopsis thaliana and Marchantia polymorpha.

The core G protein signaling module, which consists of Gα and extra-large Gα (XLG) subunits coupled with the Gβγ dimer, is a master regulator of various stress responses. In this study, we compared the basal and salt stress-induced transcriptomic, metabolomic and phenotypic profiles in Gα, Gβ, and XLG-null mutants of two plant species, Arabidopsis thaliana and Marchantia polymorpha , and showed that G protein mediates the shift of transcriptional and metabolic homeostasis to stress readiness status. We demonstrated that such stress readiness serves as an intrinsic protection mechanism against further stressors through enhancing the phenylpropanoid pathway and abscisic acid responses. Furthermore, WRKY transcription factors were identified as key intermediates of G protein-mediated homeostatic shifts. Statistical and mathematical model comparisons between A. thaliana and M. polymorpha revealed evolutionary conservation of transcriptional and metabolic networks over land plant evolution, whereas divergence has occurred in the function of plant-specific atypical XLG subunit. Taken together, our results indicate that the shifts in transcriptional and metabolic homeostasis at least partially act as the mechanisms of G protein-coupled stress responses that are conserved between two distantly related plants. Heterotrimeric G protein mutants show altered plant responses to various abiotic and biotic stresses, but the underlying molecular mechanisms remain largely unclear. This study shows that G protein regulates cell stress readiness through modulating WRKY transcriptional pathways and phenylpropanoid metabolic homeostasis. The transcriptional and metabolic networks regulated by G proteins are largely conserved between Arabidopsis thaliana and Marchantia polymorpha. [ABSTRACT FROM AUTHOR]