Genes of the RAV Family Control Heading Date and Carpel Development in Rice

In plants, correct formation of reproductive organs is critical for successful seedset and perpetuation of the species. Plants have evolved different molecular mechanisms to coordinate flower and seed development at the proper time of the year. Among the plant-specific RELATED TO ABI3 AND VP1 (RAV) family of transcription factors, only TEMPRANILLO1 (TEM1) and TEM2 have been shown to affect reproductive development in Arabidopsis (Arabidopsis thaliana). They negatively regulate the floral transition through direct repression ofFLOWERING LOCUS TandGIBBERELLIN 3-OXIDASE1/2, encoding major components of the florigen. Here we identifyRAVgenes from rice (Oryza sativa), and unravel their regulatory roles in key steps of reproductive development. Our data strongly suggest that, like TEMs, OsRAV9/OsTEM1 has a conserved function as a repressor of photoperiodic flowering upstream of the floral activatorsOsMADS14andHd3a, through a mechanism reminiscent of that one underlying floral transition in temperate cereals. Furthermore,OsRAV11andOsRAV12may have acquired a new function in the differentiation of the carpel and the control of seed size, acting downstream of floral homeotic factors. Alternatively, this function may have been lost in Arabidopsis. Our data reveal conservation ofRAVgene function in the regulation of flowering time in monocotyledonous and dicotyledonous plants, but also unveil roles in the development of rice gynoecium. RELATED TO ABI3 AND VP1 (RAV) gene function is conserved in the regulation of flowering time in monocots and dicots, although via different mechanisms, and reveal roles in rice gynoecium development.