Cloning And Functional Analysis Of Grain Width And Weight QTL TGW2 In Rice

Food is the foundation of human existence and development,which is the prerequisite of human civilization’s survival and development.With the deterioration of the global climate and bad environmental resources and reduction in arable land,grain acreage and productivity decreased.Therefore,how to increase food production has become an issue of universal concern.Rice(Oryza sativa L.)is one of the most important crops.Grain yield is a complex trait determined by its three component traits(number of panicles,number of grains per panicle,and grain weight)in rice.Grain weight as one of yield components factors directly affect the yield of rice,while the main factors affecting grain weight including grain width,grain length,grain thickness and aspect ratio.In this study,using a recombinant inbred line population composed of 132 lines derived from cross between indica rice variety 93-11 and small-grain cultivar PA64s,three QTLs for grain width along with two QTLs for grain weight were identified.Through investigation into large scale BC4F2 population,map-based cloning of a QTL related to grain width and weight,TGW2 was cloned,which encodes a cell number regulator(OsCNR1).It’s protein localized to the plasma membrane.A single nucleotide polymorphism(SNP)variation at 1818 bp upstream of TGW2 is responsible for its different expression,leading to alteration in grain width and weight by influencing cell proliferation and expansion in glumes.TGW2 interacts with KRP1,a regulator of cell cycle in plant,to negatively regulate grain width and weight.Genetic diversity analysis of TGW2 in 141 rice accessions revealed it as a breeding target in a selective sweep region.Our findings provide new insights into the genetic mechanism underlying grain morphology and grain weight,and uncover a promising gene for improving rice yield.