Characterization of the OsCCR10, a Lignin Biosynthesis Gene Involved in Rice Drought Tolerance Mechanism

Abstract

Drought is a major destructive environmental stress causing remarkable reductions in crop yield worldwide. Plant have developed morphological, physiological and biochemical mechanisms that enable them to cope with negative effects of drought stress. Lignin is a major constituent of the cell walls and modification of cell wall structure by accumulating lignin is required for plants to adjust drought stress. Our previous study demonstrated that OsCCR10 (Oryza sativa CINNAMOYL-COA REDUCTASE 10) is a strong candidate which causes drought-induced lignin accumulation. In this study, I characterized molecular functions of OsCCR10 in lignin-mediated drought tolerance mechanisms. OsCCR10 expression was induced in roots of rice plants by drought, ABA and high salt treatments. Overexpression of CCR10 either whole body and root specific significantly increased drought tolerance in rice plants. OsCCR10 was detected in cytoplasm in rice protoplasts where lignin biosynthesis occurs. Enzyme assay revealed that OsCCR10 catalyzed reductions of coumaroyl-CoA and feruloyl-CoA to coumaraldehyde and coniferaldehyde. In OsCCR10 overexpressing plants, strong staining of lignin was found in outer cell layer including epidermis and vascular tissues. Moreover, lignin quantification showed that overexpression of OsCCR10 was sufficient to increase total lignin content in leaves, stems and roots of transgenic plants. Taken together, I suggest that OsCCR10 mediates drought-induced accumulation of lignin and overexpression of OsCCR10 confers drought tolerance in rice. This study will provide a leading candidate to overcome drought stress by controlling lignin biosynthesis.