The photoperiod is an important environmental stress that determines flowering time. The CONSTANS (CO) and Heading date 1 (Hd1) genes are known to be central integrators of the photoperiod pathway in Arabidopsis and rice, respectively. Although they are both members of the CONSTANS-LIKE (COL) family and have two B-boxes and a CCT domain, rice also possesses novel COL genes that are not found in Arabidopsis. Here, we demonstrate that a novel COL gene, OsCO3, containing a single B-box and a CCT domain, modulates photoperiodic flowering in rice. The circadian expression pattern of OsCO3 mRNA oscillated in a different phase from Hd1 and was similar to that of OsCO3 pre-mRNA, suggesting that the diurnal expression pattern of OsCO3 transcripts may be regulated at the transcriptional level. Overexpression of OsCO3 specifically caused late flowering under short day (SD) conditions relative to wild-type rice plants. The expression of Hd3a and FTL decreased in these transgenic plants, whereas the expression of Hd1, Early heading date 1 (Ehd1), OsMADS51, and OsMADS50 did not significantly change. Our results suggest that OsCO3 primarily controls flowering time under SD conditions by negatively regulating Hd3a and FTL expression, independent of the SD-promotion pathway.
Bibliographical noteFunding Information:
Acknowledgments We are grateful to B.S. Shin and J.H. Lee for the OsCO3 cDNA clones. This study was supported by a grant from the Plant Signaling Network Research Center, Korea Science and Engineering Foundation, Republic of Korea. S-K. Kim, Y.H. Jang and H-Y. Park were supported by a BK21 research fellowship from the Korean Ministry of Education and Human Resources Development. J.H. Lee was supported by the Korean Research Foundation Grant (KRF-2007-359-C00023) funded by Korea Government (MOEHRD).
- Floral repressor
- Single B-box
ASJC Scopus subject areas
- Plant Science