gated induction system of a systemic floral inhibitor, antiflorigen, determines obligate short-day flowering in chrysanthemums

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 42; pp. 17137 - 17142
• Main Authors: Higuchi, Yohei, Narumi, Takako, Oda, Atsushi, Nakano, Yoshihiro, Sumitomo, Katsuhiko, Fukai, Seiichi, Hisamatsu, Tamotsu
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 15.10.2013; NATIONAL ACADEMY OF SCIENCES; National Acad Sciences
• Subjects: Amino Acid Sequence; Arabidopsis; Biological Sciences; Chrysanthemum; Chrysanthemum - genetics; Chrysanthemum - metabolism; florigen; Flower buds; Flowering; Flowers; Flowers & plants; Flowers - genetics; Flowers - metabolism; Gene expression; Gene expression regulation; Gene Expression Regulation, Plant - physiology; genes; Genetic Loci - physiology; Genetics; horticulture; industry; Leaves; leucine zipper; lighting; loci; Molecular Sequence Data; Persistent vegetative states; Photoperiod; photosensitivity; phytochrome; Plant Leaves - genetics; Plant Leaves - metabolism; Plant Proteins - biosynthesis; Plant Proteins - genetics; Plants; Proteins; Rice; Scotophase; Sequence Homology, Amino Acid; Trans-Activators - biosynthesis; Trans-Activators - genetics; transcription factors
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1307617110

Photoperiodic floral induction has had a significant impact on the agricultural and horticultural industries. Changes in day length are perceived in leaves, which synthesize systemic flowering inducers (florigens) and inhibitors (antiflorigens) that determine floral initiation at the shoot apex. Recently, FLOWERING LOCUS T (FT) was found to be a florigen; however, the identity of the corresponding antiflorigen remains to be elucidated. Here, we report the identification of an antiflorigen gene, Anti-florigenic FT/TFL1 family protein (AFT), from a wild chrysanthemum (Chrysanthemum seticuspe) whose expression is mainly induced in leaves under noninductive conditions. Gain- and loss-of-function analyses demonstrated that CsAFT acts systemically to inhibit flowering and plays a predominant role in the obligate photoperiodic response. A transient gene expression assay indicated that CsAFT inhibits flowering by directly antagonizing the flower-inductive activity of CsFTL3, a C. seticuspe ortholog of FT, through interaction with CsFDL1, a basic leucine zipper (bZIP) transcription factor FD homolog of Arabidopsis . Induction of CsAFT was triggered by the coincidence of phytochrome signals with the photosensitive phase set by the dusk signal; flowering occurred only when night length exceeded the photosensitive phase for CsAFT induction. Thus, the gated antiflorigen production system, a phytochrome-mediated response to light, determines obligate photoperiodic flowering response in chrysanthemums, which enables their year-round commercial production by artificial lighting.