Favorable Alleles of Increase the Grain-Filling Rate and Yield of Rice

Hybrid rice () has been cultivated commercially for 42 years in China. However, poor grain filling still limits the development of hybrid rice. We report here the map-based cloning and characterization of the () gene present at a major-effect quantitative trait locus. We elucidated and confirmed the function of via genetic complementation experiments and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene editing in combination with genetic and molecular biological analyses. In addition, we conducted haplotype association analysis to mine the elite alleles of among 117 rice accessions. We observed that was constitutively expressed and encoded a membrane-localized protein. The allele of the rice accession Ludao ( ) improved the grain-filling rate of rice by increasing Rubisco initial activity in the Calvin cycle. Moreover, the increased expression of the cell wall invertase gene in the near isogenic line NIL- promoted the unloading of Suc during the rice grain-filling stage. A yeast two-hybrid assay indicated that the Rubisco small subunit interacts with GFR1, possibly in the regulation of the rice grain-filling rate. Evaluation of the grain-filling rate and grain yield of F1 plants harboring and the alleles of 20 hybrids widely cultivated commercially confirmed that favorable alleles of can be used to further improve the grain-filling rate of hybrid rice.