ATPG is required for the accumulation and function of chloroplast ATP synthase in Arabidopsis

The subunit II of chloroplast ATP synthase is one of the two peripheral stalks, which associates the catalytic CF₁ with membrane-spanning CF_o. Although the structural and functional roles of chloroplast ATP synthase have been extensively examined, the physiological significance of subunit II in vivo is still unclear. In this work, we identified one Arabidopsis T-DNA insertion mutant of atpG gene encoding the subunit II of chloroplast ATP synthase. The atpg null mutant displayed an albino lethal phenotype, as it could not grow photoautotrophically. Transmission electron microscopy analysis showed that chloroplasts of atpg lacked the organized thylakoid membranes. Loss of subunit II affected the accumulation of CF₁-CF_o complex, however, it did not seem to have an effect on the CF₁ assembly. The light induced ATP formation of atpg was significantly reduced compared with the wild type. Based on these results, we suggested that ATPG was essential for the accumulation and function of chloroplast ATP synthase.