Adaptation of photoperiodic control pathways produces short-day flowering in rice

The photoperiodic control of flowering is one of the important developmental processes of plants because it is directly related to successful reproduction 1 . Although the molecular genetic analysis of Arabidopsis thaliana , a long-day (LD) plant, has provided models to explain the control of flowering time in this species 2 , 3 , 4 , very little is known about its molecular mechanisms for short-day (SD) plants. Here we show how the photoperiodic control of flowering is regulated in rice, a SD plant. Overexpression of OsGI 5 , an orthologue of the Arabidopsis GIGANTEA ( GI ) gene 6 , 7 in transgenic rice, caused late flowering under both SD and LD conditions. Expression of the rice orthologue 8 of the Arabidopsis CONSTANS ( CO ) gene 9 was increased in the transgenic rice, whereas expression of the rice orthologue 10 of FLOWERING LOCUS T ( FT ) 11 , 12 was suppressed. Our results indicate that three key regulatory genes for the photoperiodic control of flowering are conserved between Arabidopsis , a LD plant, and rice, a SD plant, but regulation of the FT gene by CO was reversed, resulting in the suppression of flowering in rice under LD conditions.