Abstract
We have reported that plastidic fructose-1,6-bisphosphate aldolase (FBA) is in vivo glutathionylated and that this isozyme, FBA1, is regulated by glutathione and important for CO2 fixation. Arabidopsis plants have another two FBA isozymes (FBA2 and FBA3) in chloroplasts. Thus, to elucidate the function of FBA1 in chloroplasts, we performed functional analysis of Arabidopsis mutants of each FBA isozyme. FBA1, FBA2 and FBA3 constituted 2%, 28% and 70%, respectively, of the total plastidic FBA protein in wild-type leaves. Compared to wild-type plants, the fba1-1 mutant with 40% decreased FBA1 exhibited reduced sugar accumulation and CO2 assimilation. These phenotypes were more severe in the fba1-4 mutant with truncation of the carboxyl terminal amino acid residues in the FBA1 protein. T-DNA insertion of FBA3 restricted sugar accumulation but did not CO2 assimilation. There was no difference in these phenotypes between wild-type plant and T-DNA insertional mutant of FBA2. These results indicate that the FBA1 plays an important role in maintenance of chloroplasts. Based on these findings, we will discuss the function of FBA1 in the Calvin cycle.
