Overexpression of OsMYB1R1-VP64 fusion protein increases grain yield in rice by delaying flowering time.

VP64 is widely used as a transcriptional activator to investigate the biological function of genes, but its potential for application in genetic improvement of crops has not been fully investigated. Here, we characterized an OsMYB1R1-VP64 fusion protein that enhanced the grain yield of rice cultivar 'Kita-ake' by 35%. OsMYB1R1-VP64 regulated grain yield of transgenic plants mainly by extending the vegetative growth stage. Further analysis indicated that OsMYB1R1-VP64 delayed flowering by down-regulating expression of Heading date 3a (Hd3a) and RICE FLOWERING LOCUST 1 (RFT1) through repression of Early heading date 1 (Ehd1). The expression pattern of OsMYB1R1 was constitutive and rhythmically controlled. OsMYB1R1 protein had transcriptional activation activity and was localized to the nucleus. Our findings suggest that the OsMYB1R1-VP64 construct can be used to increase grain yield in rice.