Characterization of an Abc1 kinase family gene OsABC1-2 conferring enhanced tolerance to dark-induced stress in rice.

Leaf senescence is a complex and highly organized process resulting in numerous changes of gene expression and metabolic procedures. However, the exact mechanisms underlying these changes are not well understood. In this study, we reported a rice (Oryza sativa) T-DNA insertion mutant impaired in an Abc1 kinase family gene with a dwarf and pale-green phenotype. The mutant showed reduced pigment content and photosynthetic efficiency and increased superoxide dismutase activity in leaves. The mutated gene, designated OsABC1-2, is expressed primarily in green tissues and/or organs and encodes a protein localized in chloroplast envelope. Expression of the gene was drastically suppressed by dark treatment. Overexpression of the gene in rice enhanced tolerance to prolonged dark-induced stress. Phylogenetic analysis revealed that the plant Abc1 proteins could be divided into three subgroups and OsAbc1-2 resides in a subgroup with potential chloroplast origin. Our results suggest that divergence has occurred among plant Abc1 family and chloroplast Abc1 kinases play potential roles in regulating dark-induced senescence of plants.