Isolation of Mutants Exhibiting the Low Activity of the Plasma Membrane H⁺-ATPase in Arabidopsis Roots

Abstract

The plasma membrane H⁺-ATPase is a master enzyme that creates a driving force to uptake the many ions, and controls the cell expansion. It has been demonstrated that phosphorylation of a penultimate Thr in the C-terminus is required for activation of the H⁺-ATPase in planta. However, signaling components leading to activation of the H⁺-ATPase has yet to be identified. In order to identify the components, we screened and isolated the mutants exhibiting low pH-hypersensitive in root growth, since the H⁺-ATPase activity is prerequisite for the root growth. We further characterized one of them, E8-4 mutant. The E8-4 roots grew slower than wild type, especially in low pH condition. Interestingly, we found that both the H⁺-ATPase activity and phosphorylation level of the penultimate Thr of the H⁺-ATPase in roots of E8-4 were lower that those of wild type under normal pH condition. We are trying to identify the E8-4 locus by map-based cloning and characterize expression of the H⁺-ATPase isoforms in E8-4 mutant. We will repot these results.