Grain size substantially influences rice quality and yield. In this study, we identified CONTROL OF SLENDER RICE 1 ( COR1 ), a quantitative trait locus encoding an F-box protein that enhances grain length by promoting cell proliferation. The transcription factor OsbZIP35 represses COR1 expression, while COR1 interacts with OsTCP19, leading to its degradation. Knockout of either OsbZIP35 or OsTCP19 results in increased grain length, confirming their regulatory roles in grain development. The OsbZIP35-COR1-OsTCP19 module controls the expression of the cell cycle gene OsCycB1;4 , thereby modulating cell proliferation and ultimately determining grain size. Five haplotypes of COR1 were identified, with COR1 -Hap1 and COR1 -Hap3 being elite alleles associated with longer grains. Field plot trials demonstrated that the near-isogenic line NIL- COR1 ^SLG increased yield by ~6.6% compared to NIL- COR1 ^Nip . These findings elucidate the genetic mechanisms underlying grain size regulation and offer promising strategies for improving rice yield.

Rice (Oryza sativa L.) leaf rolling enhances canopy architecture and photosynthetic efficiency, thereby improving yield potential. Through genome-wide association studies (GWAS) of 802 Xian and Geng rice accessions, we identified 32 loci associated with the leaf rolling index (LRI) and characterized OUTWARD ROLLED LEAF 4 (ORL4) as a regulatory gene from natural germplasm. CRISPR/Cas9-mediated knockout of ORL4 resulted in abaxially rolled leaves, driven by excessive bulliform cell proliferation and disrupted vascular patterning. A promoter variant (Chr04_19562737-C/T) modulates ORL4 expression by altering the binding affinity of the transcription factor RICE OUTERMOST CELL-SPECIFIC 8 (ROC8). Carriers of the ORL4C allele exhibit stronger ROC8 binding, higher ORL4 expression, and adaxially rolled or flat leaves; ORL4T carriers show the opposite phenotype. ORL4 forms a ternary complex with ROC8 and TOPLESS-RELATED PROTEIN 2(TPL2) to suppress ABAXIALLY CURLED LEAF 1(ACL1), a positive regulator of bulliform cell differentiation. Evolutionary analyses indicated that the ORL4C and ORL4T alleles originated from Oryza nivara and Oryza rufipogon, with ORL4C favored in Geng and ORL4T in Xian during domestication. Promoter editing of ORL4 in the elite cultivar “Shennong 89-366” generated lines with enhanced LRI, achieving a significant yield increase in field trials. This study elucidates the genetic and molecular basis of leaf rolling and provides a promising strategy for rice yield improvement via precise promoter editing.