Photoperiod-insensitive floral transition in chrysanthemum induced by constitutive expression of chimeric repressor CsLHY-SRDX. (June 2017)

• Record Type: Journal Article
• Authors: Oda, Atsushi; Higuchi, Yohei; Hisamatsu, Tamotsu
• Is Part Of: Plant science. Volume 259(2017)
• Page Start: 86
• Page End: 93
• Publication Date: 2017-06
• Subjects: Chrysanthemum -- Circadian rhythm -- Flowering -- LATE ELONGATED HYPOCOTYL; Botany -- Periodicals; Botanique -- Périodiques; 580
• DOI: 10.1016/j.plantsci.2017.03.007
• Languages: English
• ISSNs: 0168-9452

Abstract

Highlights: CsLHY - SRDX does not cause a severe defect in the circadian clock. CsLHY-SRDX shows photoperiod-insensitive floral transition. Both CsFTL3 and CsAFT are downregulated in CsLHY-SRDX. CsLHY plays important roles in photoperiodic flowering in chrysanthemum. Abstract: A wide variety of physiological processes including flowering are controlled by the circadian clock in plants. In Arabidopsis, LATE ELONGATED HYPOCOTYL ( LHY ) and CIRCADIAN CLOCK ASSOCIATED 1 ( CCA1 ) constitute the central oscillator, and their gain of function and loss of function disrupt the circadian clock and affect flowering time through FLOWERING LOCUS T ( FT ), a gene encoding a florigen. Chrysanthemum is a typical short-day (SD) plant and responds to shortening of day length by the transition from the vegetative to reproductive phase. We identified FLOWERING LOCUS T-LIKE 3 (FTL3) and ANTI-FLORIGENIC FT/TFL1 FAMILY PROTEIN (AFT) as a florigen and antiflorigen, respectively, in a wild diploid chrysanthemum ( Chrysanthemum seticuspe f. boreale ). CsFTL3 and CsAFT are induced under SD or a noninductive photoperiod, respectively, and their balance determines the floral transition and anthesis. Meanwhile, the time-keeping mechanism that regulates the photoperiodic flowering in chrysanthemum is poorly understood. Here, we focused on a LHY / CCA1 -like gene called CsLHY in chrysanthemum. We fused CsLHY to a gene encoding short transcriptional repressor domain ( SRDX ) and constitutively expressed it in chrysanthemum. Although the transcription of clock-related genes was conditionally affected, circadian rhythm was not completely disrupted in CsLHY-SRDX transgenic plants. These plants formed almost the same number of leaves before floral transition under SD and long-day conditions. Thus, CsLHY-SRDX chrysanthemum showed photoperiod-insensitive floral transition, but further development of the capitulum was arrested, and anthesis was not observed. Simultaneously with the flowering phenotype, CsFTL3 and CsAFT were downregulated in CsLHY-SRDX transgenic plants. These results suggest that CsLHY-SRDX affects CsFTL3 and CsAFT expression and causes photoperiod-insensitive floral transition without a severe defect in the circadian clock.