Abstract
A carrot mutant cell line, which was selected in Al-phosphate medium previously, could utilize the phosphate from Al-phosphate by enhanced citrate excretion. Physiological studies of citrate efflux from the mutant indicated that this system would be consisted of anion channel and PM H+-ATPase. The mutant releases electrochemically equivalent H+ during citrate excretion from the PM, which is possibly depended on its higher activity of PM H+-ATPase. In this study, we further characterized PM H+-ATPase in the mutant by molecular biological approaches. We isolated six kind of cDNAs encoding PM H+-ATPase by de-generate PCR. Transcriptional analysis revealed that DcPA1;1 gene, which is most abundant isoform in the mutant, was three times higher than that of wild type cells. Anti-sense reduction of DcPA1;1 in the mutant caused significant decrease of citrate excretion. These results indicate that higher PM H+-ATPase activity in the mutant was essential for its greater ability of citrate excretion.
