Genome editing of RICE FLOWERING LOCUS T 1 promoter delayed flowering in rice

The heading date of rice is a crucial agronomic traits affecting regional adaptation and grain productivity. Manipulating the vegetative growth period or delaying flowering can increase the yield and quality. The RICE FLOWERING LOCUS T (RFT1) has a critical role in flowering regulation. Here, we aimed to delay flowering in rice by reducing the expression of RFT1. For this purpose, we targeted four sites within the 0.5-kb region of RFT1 promoter for gene editing. Six homozygous mutant lines were obtained (rft1 pro-1 to rft1 pro-6), which showed delayed heading dates by 1.4-9.2 days. In addition, expression levels of Hd3a and RFT1 were significantly reduced, corroborating the late flowering phenotype. Using a dual-luciferase reporter in rice protoplast, we established that the protein level of LUC driven by the edited rft1 promoter was lower than that driven by the RFT1 promoter. In conclusion, we have developed a viable strategy to delay rice flowering by editing promoter of flower-promoting gene.