We characterized the function of the rice cytosolic hexokinase Os HXK7(Oryza sativa Hexokinase7),which is highly upregulated when seeds germinate under O_2-deficient conditions. According to transient expression assays that used the promoter:luciferase fusion construct,Os HXK7 enhanced the glucose(Glc)-dependent repression of a rice a-amylase gene(RAmy3D) in the mesophyll protoplasts of maize,but its catalytically inactive mutant alleles did not. Consistently,the expression of Os HXK7,but not its catalytically inactive alleles,complemented the Arabidopsis glucose insensitive2-1(gin2-1) mutant,thereby resulting in the wild type characteristics of Glc-dependent repression,seedling development,and plant growth. Interestingly,Os HXK7-mediated Glc-dependent repression was abolished in the O_2-deficient mesophyll protoplasts of maize. This result provides compelling evidence that Os HXK7 functions in sugar signaling via a glycolysis-dependent manner under normal conditions,but its signaling role is suppressed when O_2 is deficient. The germination of two null Os HXK7 mutants,oshxk7-1 and oshxk7-2,was affected by O_2 deficiency,but overexpression enhanced germination in rice. This result suggests the distinct role that OsH XK7 plays in sugar metabolism and efficient germination by enforcing glycolysis-mediated fermentation in O_2-deficient rice. We characterized the function of the rice cytosolic hexokinase Os HXK7 (Oryza sativa Hexokinase 7), which is highly upregulated when the seeds are germinate under O 2-deficient conditions. According to transient expression assays that used the promoter: luciferase fusion construct, Os HXK7 enhanced the glucose Glc) -dependent repression of a rice a-amylase gene (RAmy3D) in the mesophyll protoplasts of maize, but its catalytically inactive inactive mutant alleles did not. Consistently, the expression of Os HXK7, but not its catalytically inactive alleles, complemented the Arabidopsis glucose Interestingly, Os HXK7-mediated Glc-dependent repression was abolished in the O 2-deficient mesophyll protoplasts of insects, which resulted in the wild type characteristics of Glc-dependent repression, seedling development, and plant growth. maize. This result provides compelling evidence that Os HXK7 functions in sugar signaling via a glycolysis-dependent manner under normal conditions, but its signaling role is suppressed when O_2 is deficient. The germination of two null Os HXK7 mutants, oshxk7-1 and oshxk7-2, was affected by O_2 deficiency, but overexpression enhanced germination in rice. This result suggests the distinct role that OsH XK7 plays in sugar metabolism and efficient germination by enforcing glycolysis-mediated fermentation in O_2-deficient rice.