Functional Identification of Genes Encoding CCT Domain in Rice

CCT-domain containing genes in plants are frequently involved into the flowering pathway. Two key flowering genes CO in long day plant Arabidopsis and Hd1 in short day plant rice shared the common CCT domain. There are 45 members of the CCT family in rice including 31 in indica and 40 in japonica (26 are both in indica and japonica). They are distributed on all 12 chromosomes, and preferably located on chromosomes 2 and 6. Several studies showed that heading date QTLs such as Ghd7 and Ghd8 are coincidently detected in the region harbored genes in CCT family. In order to systematically identify function of the genes of CCT family, we isolated 20 genes of the CCT family from japonica rice Nipponbare or indica rice Minghui 63. They were introduced to japonica variety Zhonghua 11 or Hejiang 19 by Agrobacterium-mediated transformation, respectively. 6 of the 20 genes, their over-expression plants delayed heading up to 10 to 30 days under long day conditions (LD). Segregation test in their T1 generations confirmed that these genes control the heading date change. Meanwhile, 8 of them, the RNAi plants are on the process of T0 generation. Besides heading date change, transgenic plants of CCT1 also have effects on other traits. That is, over-expression plant shows a dwarf plant height, larger leaf angle and decreased tillers and panicles relative to wild-type zhonghua11. The expression level of Ehd1 increased in the CCT1 transgenic plants, whereas Hd3a and RFT1 decreased, which resulted a delayed heading under LD conditions. We are struggling for isolating the other members of CCT family and continuously identify their function.