Rice FLAVIN‐BINDING, KELCH REPEAT, F‐BOX 1 (OsFKF1) promotes flowering independent of photoperiod

Abstract In the facultative long‐day ( LD ) plant A rabidopsis thaliana , FLAVIN‐BINDING , KELCH REPEAT , F‐BOX 1 ( FKF1 ) is activated by blue light and promotes flowering through the transcriptional and post‐translational regulation of CONSTANS under inductive LD conditions. By contrast, the facultative short day ( SD ) plant rice ( O ryza sativa ) flowers early under inductive SD and late under non‐inductive LD conditions; the regulatory function of OsFKF1 remains elusive. Here we show that osfkf1 mutants flower late under SD , LD and natural LD conditions. Transcriptional analysis revealed that OsFKF1 up‐regulates the expression of the floral activator Ehd2 and down‐regulates the expression of the floral repressor Ghd7 ; these regulators up‐ and down‐regulate Ehd1 expression, respectively. Moreover, OsFKF1 can up‐regulate Ehd1 expression under blue light treatment, without affecting the expression of Ehd2 and Ghd7 . In contrast to the LD ‐specific floral activator Arabidopsis FKF1 , OsFKF1 likely acts as an autonomous floral activator because it promotes flowering independent of photoperiod, probably via its distinct roles in controlling the expression of rice‐specific genes including Ehd2 , Ghd7 and Ehd1 . Like Arabidopsis FKF1 , which interacts with GI and CDF1 , OsFKF1 also interacts with OsGI and OsCDF1 (also termed OsDOF12 ). Thus, we have identified similar and distinct roles of FKF1 in Arabidopsis and rice.