Abstract
In the absolute short-day (SD) plant Pharbitis nil, flowering can be induced by a single dark period just after cotyledons are fully opened. It has been postulated that during the inductive dark period, floral stimulus is produced in the cotyledons, and then transported to the shoot apex (SA). Recent studies in Arabidopsis indicated that FT has critical roles for flowering. We had isolated Pharbitis two FT homologs, LEAF-TYPE (PnFTL) and APICAL-TYPE (PnFTA), whose expression was observed in leaf and SA, respectively, only under SD conditions. Moreover, they were repressed by night-break treatment. Ectopic expression of PnFTL caused flower bud formation directly on unorganized callus. RNAi plants that showed reduced PnFTL and PnFTA expression abolished the 1SD induction of flowering. Our results indicate that apical type FT in addition to leaf type FT may be involved in flowering in Pharbitis nil.
