The calcium sensor CBL10 negatively regulates plasma membrane H+-ATPase activity and alkaline stress response in Arabidopsis

Plasma membrane (PM) H+-ATPase (AHA) provides energy to some important physiological and biochemical processes in plant cells, playing a key role in plant growth and development. Here, we found that the growth and PM H+-ATPase activity of the Arabidopsis cbl10 mutant was lower than the wild-type plant (WT) under salinity stress, suggesting that the calcineurin B-like protein 10 (CBL10) might be involved in the regulation of AHA. In contrast, cbl10 grew better than WT when exposure to external higher pH stress, and the growth of cbl10 plant expressing CBL10 gene was similar as WT under external high pH. Under alkaline conditions, the proton influx rate of cbl10 mutant was slower than that of WT, and the pH in the plate area where cbl10 mutant grew was lower compared to WT plates. Yeast two-hybrid and BiFC assays showed that CBL10 bound to the C-terminus of AtAHA4 or AtAHA11, such that the growth of yeast cells coexpressing CBL10 and AHA4/AHA11 was worse than transgenic cells with a single AHA4 or AHA11. This suggests that CBL10 negatively regulates PM H+-ATPase activity by directly interacting with AtAHA4 or AtAHA11, which decreases the ability of Arabidopsis to adapt to alkaline environment. Overall, this study indicates that CBL10 may function as an interconnecting regulator to coordinate plant responses to saline and alkaline stresses.