Abstract
We have shown that FD acts with FT in the floral transition during Arabidopsis development. FD gene encodes a bZIP protein and may act as a transcription factor. We examined the expression of meristem identity genes (AP1, CAL, and FUL), which are candidates for the FD targets. AP1, CAL, and FUL mRNA levels were greatly reduced in fd-1; lfy-26 inflorescences and were increased in 35S::FD seedlings, suggesting the role of FD in up-regulation of these genes. Expression of AP1(1.7 kb)::GUS in 35S::FD seedlings was restricted to the vascular tissues of cotyledons and leaves, suggesting the involvement of additional factor which is likely FT. In 35S::FD; ft-3 seedlings, the expression of AP1 was reduced to wild-type level. FD protein can interact with FT protein in yeast cells. Taken together, these results suggest that FD requires FT for up-regulation of its target, AP1 during the transition to flowering.
