Cytokinin Oxidase Regulates Rice Grain Production

TLDR

Agricultural traits are largely governed by quantitative trait loci derived from natural allelic variation. Lower OsCKX2 expression leads to cytokinin buildup in inflorescence meristems, boosting reproductive organ number and grain yield, while QTL pyramiding of grain‑number and plant‑height loci produces lines with both advantages. The QTL Gn1a encodes cytokinin oxidase/dehydrogenase (OsCKX2), and its manipulation offers a strategy for customized crop improvement.

Abstract

Most agriculturally important traits are regulated by genes known as quantitative trait loci (QTLs) derived from natural allelic variations. We here show that a QTL that increases grain productivity in rice, Gn1a, is a gene for cytokinin oxidase/dehydrogenase (OsCKX2), an enzyme that degrades the phytohormone cytokinin. Reduced expression of OsCKX2 causes cytokinin accumulation in inflorescence meristems and increases the number of reproductive organs, resulting in enhanced grain yield. QTL pyramiding to combine loci for grain number and plant height in the same genetic background generated lines exhibiting both beneficial traits. These results provide a strategy for tailormade crop improvement.