title: Day light quality affects the night-break response in the short-day plant chrysanthemum, suggesting differential phytochrome-mediated regulation of flowering.
abstract: Chrysanthemum (Chrysanthemum morifolium) is a short-day plant, which flowers when the night length is longer than a critical minimum. Flowering is effectively inhibited when the required long-night phase is interrupted by a short period of exposure to red light (night break; NB). The reversal of this inhibition by subsequent exposure to far-red (FR) light indicates the involvement of phytochromes in the flowering response. Here, we elucidated the role of light quality in photoperiodic regulation of chrysanthemum flowering, by applying a range of different conditions. Flowering was consistently observed under short days with white light (W-SD), SD with monochromatic red light (R-SD), or SD with monochromatic blue light (B-SD). For W-SD, NB with monochromatic red light (NB-R) was most effective in inhibiting flowering, while NB with monochromatic blue light (NB-B) and NB with far-red light (NB-FR) caused little inhibition. In contrast, for B-SD, flowering was strongly inhibited by NB-B and NB-FR. However, when B-SD was supplemented with monochromatic red light (B+R-SD), no inhibition by NB-B and NB-FR was observed. Furthermore, the inhibitory effect of NB-B following B-SD was partially reversed by subsequent exposure to a FR light pulse. The conditions B-SD/NB-B (no flowering) and B+R-SD/NB-B (flowering) similarly affected the expression of circadian clock-related genes. However, only the former combination suppressed expression of the chrysanthemum orthologue of FLOWERING LOCUS T (CmFTL3). Our results suggest the involvement of at least 2 distinct phytochrome responses in the flowering response of chrysanthemum. Furthermore, it appears that the light quality supplied during the daily photoperiod affects the light quality required for effective NB.
authors: NARO Institute of Floricultural Science-NIFS, National Agriculture and Food Research Organization-NARO, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8519, Japan.
authors: Yohei
authors: Y
authors: Higuchi
authors: Katsuhiko
authors: K
authors: Sumitomo
authors: Atsushi
authors: A
authors: Oda
authors: Hiroshi
authors: H
authors: Shimizu
authors: Tamotsu
authors: T
authors: Hisamatsu
mesh_terms: D031202:Chrysanthemum / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*; D057906:Circadian Clocks; D018076:DNA, Complementary; D003624:Darkness; D035264:Flowers / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*; D018506:Gene Expression Regulation, Plant; D008027:Light; D017440:Photoperiod; D010834:Phytochrome / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D010834:Phytochrome