Gα Protein Mediates High-Concentration CO2-Induced Stomata Closure Through Interaction With Carbonic Anhydrase to Promote Guard Cell Hydrogen Peroxide Production in Arabidopsis.

Guard cells detecting fluctuations in ambient CO2 levels and modulating stomatal aperture constitute a crucial adaptive response to changes of atmospheric CO2 in plants. CO2 sensing in animals is closely related to G proteins. Nonetheless, the role of G proteins in high-concentration CO2-regulated stomatal movement in plants remains unclear. Using NaHCO3 as a CO2 source, the results of this study showed that NaHCO3-induced stomatal closure and guard cell hydrogen peroxide (H2O2) production in wild type plants were disrupted by Gα inhibitor pertussis toxin (PTX) and in mutants gpa1, cGα/DF, and wGα/DF but not in cGa and wGa lines. Furthermore, NaHCO3 upregulated the expression of GPA1 during the early phases of NaHCO3-induced stomatal closure. Additionally, Gα activator cholera toxin (CTX) failed to rescue NaHCO3-induced stomatal closure in wild type plants treated with carbonic anhydrase (CA) inhibitors EZ and AZ, as well as in ca1ca4 mutant. NaHCO3 also did not induce stomatal closure in cGα/ca1ca4 and wGα/ca1ca4 mutants. Notably, NaHCO3-increased CA enzymatic activity was abolished in wild type plants treated with PTX and in gpa1 mutant but remained unaffected in cGa and wGa lines. Moreover, LCI, Pull-down and Co-IP assays displayed that GPA1 interacts with CA1 and CA4. And, NaHCO3-induced guard cell H2O2 production impaired by ca1ca4, cGα/ca1ca4 and wGα/ca1ca4 mutants. These findings demonstrate that Gα subunit GPA1 mediates high-concentration CO2-induced stomatal closure by interaction with CA1 and CA4 to promote H2O2 accumulation in Arabidopsis guard cells. This insight advances our understanding of CO2-governing stomatal movement in plants.