Identification And Analysis Of CYO2, Homolog Of A Cotyledon Chloroplast Development Factor CYO1 That Has Protein Disulfide Isomerase, In Arabidopsis thaliana.

Abstract

CYO1 has protein disulfide isomerase activity, and functions as a cotyledon-specific chloroplast biogenesis factor in Arabidopsis thaliana. We screened the CYO1 homolog that function as the chloroplast biogenesis factors at all green tissues by a plastid proteome database and Arabidopsis T-DNA lines. cyo2 mutant has both albino leaves and cotyledons. The maximum quantum yield of photosystem II (PSII) and the electron transport rate in the mutant were much decreased. The amounts of PSI and PSII core subunits in the mutant were significantly decreased compared with those in wild type. The expression of CYO2::GUS was detected at all green tissues. Recombinant CYO2 accelerated disulfide bond reduction in the model substrate insulin, indicating that CYO2 had protein disulfide isomerase activity. These results suggest that CYO2 is a chloroplast biogenesis factor at all green tissues in A. thaliana.