OsCOL10, a CONSTANS-Like Gene, Functions as a Flowering Time Repressor Downstream of Ghd7 in Rice.

Flowering time, or heading date, is a critical agronomic trait that determines the cropping season and regional adaptability, and ultimately grain yield in rice. A number of genes involved in photoperiodic flowering have been cloned and their roles in modulating expression of the flowering genes have been characterized to a certain extent. However, much less is known about the pathway in transmitting the day length response signal(s) to induce transition to reproductive growth. Here, we report a constitutive flowering repressorOsCOL10, which encodes a member of the CONSTANS-like (COL) family. Transgenic rice plants overexpressingOsCOL10(driven by a strong promoter or by fusing it to the activation domain of VP64) showed delayed flowering time under both short and long days.OsCOL10is affected by the circadian clock and is preferentially expressed in leaf mesophyll cells; it is localized to the nucleus and has transcriptional activation activity. Further studies show thatOsCOL10represses the expression of theFT-like genesRFT1andHd3athroughEhd1.Transcripts ofOsCOL10are more abundant in plants carrying a functionalGhd7allele or overexpressingGhd7than inGhd7-deficient plants, thus placingOsCOL10downstream ofGhd7.Taking these findings together, we conclude thatOsCOL10functions as a flowering time repressor that linksGhd7andEhd1in rice.

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