Plasma membrane H+-ATPase activation increases global transcript levels and promotes the shoot growth of light-grown Arabidopsis seedlings.

(1) Plant cell growth require the elongation of cells mediated by cell wall remodelling and turgor pressure changes. The plasma membrane (PM) H+-ATPase facilitates both cell wall remodelling and turgor pressure changes, by acidifying the apoplast of cells, referred to as acid growth. The acid growth theory is mostly established on the auxin-induced activation of PM H+-ATPase in non-photosynthetic tissues. However, how PM H+-ATPase affect the growth in photosynthetic tissues of Arabidopsis remains unclear. (2) Here, a combination of transcriptomics and cis-regulatory element analysis was conducted to identify the impact of PM H+-ATPase on global transcript levels and the molecular mechanism downstream of the PM H+-ATPase. (3) The PM H+-ATPase activation increased transcript levels globally, especially cell wall modification-related genes. The transcript level changes were in PM H+-ATPase-dependent manner. Involvement of Ca2+ was suggested as CAMTA motif was enriched in the promoter of PM H+-ATPase-induced genes and cytosolic Ca2+ elevated upon PM H+-ATPase activation. (4) PM H+-ATPase activation in photosynthetic tissues promote the expression of cell wall modification enzymes and shoot growth, adding a novel perspective of photosynthesis-dependent PM H+-ATPase activation in photosynthetic tissues to the acid growth theory that has primarily based on findings from non-photosynthetic tissues.