Genes of the RAV family control heading date and carpel development in rice

In plants, correct formation of reproductive organs is critical for successful seed-set and perpetuation of the species. Plants have evolved different molecular mechanisms to co-ordinate 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 TEM-PRANILLO1 (TEM1) and TEMPRANILLO2 (TEM2) have been shown to affect reproduc-tive development in Arabidopsis (Arabidopsis thaliana). They negatively regulate floral transition through direct repression of FLOWERING LOCUS T and GIBBERELLIN 3-OXIDASE1/2, encoding major components of the florigen. Here we identify RAV genes 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 con-served function as a repressor of photoperiodic flowering upstream of the floral activators OsMADS14 and Hd3a, through a mechanism reminiscent of that one underlying floral transition in temperate cereals. Furthermore, OsRAV11 and OsRAV12 may have ac-quired a novel 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 of RAV gene function in the regulation of flowering time in monocotyledonous and dicotyledonous plants, but also unveil roles in the development of rice gynoecium.