Ghd7 is important for increasing rice productivity and adaptability. It is a major regulator of Ehd1 and could delay flowering by repressing Ehd1 under LD (Takahashi et al., 2009; Xue et al., 2008). As Ghd7 encodes a CCT (CONSTANS, CO-like, and TOC1) domain protein, which shows very low homology to Arabidopsis genome, the Ghd7-Ehd1 may be a unique pathway in rice (Koo et al., 2013; Xue et al., 2008). Further study shows that Ghd7 and Ehd1 can respectively set a daylength threshold for Hd3a expression,
which is usually observed in SD plants but not in LD plants (Itoh et al., 2010; Takimoto and Ikeda, 1961), and this capacity of discernment in critical day length in rice greatly enriches the daylength-dependent regulated mechanism of florigen gene expression.