SCaBP3/CBL7 negatively regulates the plasma membrane H-ATPase and modulates hypocotyl elongation in .

The regulation of hypocotyl elongation is an important process in plant growth and development and depends on the activity of the plasma membrane (PM) H-ATPase. In this study, we found that the Arabidopsis protein SOS3-LIKE CALCIUM BINDING PROTEIN3 (SCaBP3) negatively regulates PM H-ATPase activity in yeast and hypocotyl elongation in dark-grown seedlings. Yeast two-hybrid assays showed that SCaBP3 interacts with representative members of the Arabidopsis PM H-ATPase family. Experiments in RS-72 yeast showed that SCaBP3 negatively regulates PM H-ATPase activity-dependent yeast cell growth. Hypocotyl elongation was promoted in the loss-of-function mutant and inhibited in overexpression lines of Arabidopsis. We propose that SCaBP3 modulates hypocotyl elongation by negatively regulating PM H-ATPase activity.