Enhanced saccharification yields from rice straw by senescence-induced expression of a cytokinin biosynthesis gene in intragenic rice plants

Controlling the digestibility of cellulosic biomass is important for its efficient use. We generated intragenic rice plants showing enhanced saccharification yield of rice straw. The rice cytokinin biosynthesis gene, LONELY GUY, under the control of the rice senescence-inducible STAY GREEN promoter, was introduced into the rice genome via particle bombardment. The rice-derived herbicide resistance gene ALS(G95A) was used as a selection marker gene. Regenerated intragenic rice plants with no foreign sequences showed enhanced saccharification yields from the leaves at harvest, whereas no significant differences were observed at the heading stage. Because the saccharification yields of rice straw are reduced after senescence, which is suppressed by cytokinin, we propose that the enhanced saccharification yields of intragenic rice plants are caused by the delay in senescence of the rice leaves due to the expression of the introduced cytokinin biosynthesis gene upon senescence.