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

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 scabp3 and inhibited in SCaBP3 overexpression lines of Arabidopsis. We propose that SCaBP3 modulates hypocotyl elongation by negatively regulating PM H + -ATPase activity.