Sucrose preferentially promotes expression of and to enhance defense response to blast fungus in rice.

Sucrose controls various developmental and metabolic processes in plants. It also functions as a signaling molecule in the synthesis of carbohydrates, storage proteins, and anthocyanins, as well as in floral induction and defense response. We found that sucrose preferentially induced , whereas other sugars (such as mannitol, glucose, fructose, galactose, and maltose) did not have the same effect. A hexokinase inhibitor mannoheptulose did not block the effect of sucrose, which is consequently thought to function directly. MG132 inhibited sucrose induction, suggesting that a repressor upstream of is degraded by the 26S proteasome pathway. The 3-kb promoter sequence of was preferentially induced by sucrose in the luciferase system. Knockout mutants of were more sensitive to the rice blast fungus , whereas the overexpression of enhanced the resistance, indicating that this gene is a positive regulator in the plant defense against this pathogen. The luciferase activity driven by the promoter was induced by OsWRKY7 and this transcription factor bound to the promoter region of , suggesting that OsWRKY7 directly controls the expression of . We conclude that sucrose promotes the transcript level of , thereby increasing the expression of for the defense response in rice.