ABC2 protein, a cotyledon-specific chloroplast development factor of Arabidopsis, had thiol-disulfide reduction activity.

Abstract

A newly isolated Arabidopsis thaliana aberrant chloroplast (abc2 ) mutant shows cotyledon specific albino phenotype. The mutated nuclear gene encoded a novel protein that had a Zn-finger motif. The expression of the ABC2 gene was induced by light irradiation, and was detected at only young plants. Green fluorescence protein and immunoblotting assays indicated that ABC2 protein was chloroplast membrane protein. In the abc2 mutant, the plastids in cotyledon grown under light conditions were abnormal shape and did not develop the thylakoid membrane, but that grown dark conditions was same to that of wild type. ABC2 protein had the reduction activity of insulin, and the oxidative renaturation activity of reduced RNase. These results suggested that ABC2 protein had protein-disulfide isomerase activity, and is a cotyledon-specific chloroplast biogenesis factor.