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

Abstract The heading date of rice (Oryza sativa L.) is one of the crucial agronomic traits that affect regional adaptation and grain productivity. Increasing the vegetative growth period or delaying flowering can improve the yield and quality of rice. Therefore, this article uses the CRISPR/Cas9 genome editing system to slightly reduce the expression of flowering activating factors to delay rice flowering. We selected a 0.5-kb region of RICE FLOWERING LOCUS T 1 promoter (RFT1 pro). We designed four pairs of targets in this region using CRISPR-Cas9 for multiplex editing. We obtained six homozygous mutant lines named rft1 pro-1 to rft1 pro-6 by editing the RFT1 pro. The heading date of the mutant lines was delayed by 1.4–9.2 days, and the expression levels of Hd3a and RFT1 were significantly reduced, supporting the late flowering phenotype. Moreover, we found that the protein level of RFT1 was reduced in rft1 pro compared with the wild type, which indicated that editing RFT1 pro affects the translation of RFT1. In conclusion, we have found that it is a feasible method to delay rice flowering by editing the flower-promoting gene promoter. Subsequently, the flowering time of varieties can be fine-tuned by targeting the promoter regions of other genes related to flowering time.