Abstract
Chrysanthemum is a typical short-day (SD) plant and responds to shorting of day length in the transition from vegetative to reproductive phase. FLOWERING LOCUS T (FT)/ Heading date 3a (Hd3a) play a pivotal role in the induction of the phase transition and proposed to encode florigen. We isolated three FT-like genes of Chrysanthemum seticuspe f. boreale, a diploid wild chrysanthemum, CsFTL1, CsFTL2 and CsFTL3. Under SD conditions, the expressions of CsFTL1 and CsFTL2 were down-regulated, in contrast, the expression of CsFTL3 was up-regulated. Overexpression of CsFTL3 in chrysanthemum could induce flowering under non-inductive conditions. The expression levels of CsFTL3 in the two Chrysanthemum seticuspe accessions that differ in their critical day-length for flowering tightly coincided with their flowering response, the expression levels of CsFTL3 in the leaves were significantly higher under floral inductive photoperiods than non-inductive conditions in both accessions. Taken together, these results indicate that the gene product of CsFTL3 plays a similar role in the floral transition as a florigen in other plant species.
