CsFTL3, a chrysanthemumFLOWERING LOCUS T-likegene, is a key regulator of photoperiodic flowering in chrysanthemums

• Published in: Journal of experimental botany Vol. 63; no. 3; pp. 1461 - 1477
• Main Authors: Oda, Atsushi, Narumi, Takako, Li, Tuoping, Kando, Takumi, Higuchi, Yohei, Sumitomo, Katsuhiko, Fukai, Seiichi, Hisamatsu, Tamotsu
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01-01-2012
• Subjects: Amino acids; Florets; Flowering; Flowers; Gene expression regulation; Inflorescences; Leaves; Meristems; Photoperiod; Plants; RESEARCH PAPER
• ISSN: 0022-0957; 1460-2431

Chrysanthemum is a typical short-day (SD) plant that responds to shortening daylength during the transition from the vegetative to the reproductive phase.FLOWERING LOCUS T (FT)/Heading date 3a (Hd3a)plays a pivotal role in the induction of phase transition and is proposed to encode a florigen. ThreeFT-likegenes were isolated fromChrysanthemum seticuspe(Maxim.) Hand.-Mazz. f. boreale (Makino) H. Ohashi & Yonek, a wild diploid chrysanthemum:CsFTL1, CsFTL2, andCsFTL3. The organ-specific expression patterns of the three genes were similar: they were all expressed mainly in the leaves. However, their response to daylength differed in that under SD (floral-inductive) conditions, the expression ofCsFTL1andCsFTL2was down-regulated, whereas that ofCsFTL3was up-regulated.CsFTL3had the potential to induce early flowering since its overexpression in chrysanthemum could induce flowering under non-inductive conditions.CsFTL3-dependent graft-transmissible signals partially substituted for SD stimuli in chrysanthemum. TheCsFTL3expression levels in the twoC. seticuspeaccessions that differed in their critical daylengths for flowering closely coincided with the flowering response. TheCsFTL3expression levels in the leaves were higher under floral-inductive photoperiods than under non-inductive conditions in both the accessions, with the induction of floral integrator and/or floral meristem identity genes occurring in the shoot apexes. Taken together, these results indicate that the gene product ofCsFTL3is a key regulator of photoperiodic flowering in chrysanthemums.