Cool night‐time temperatures induce the expression ofCONSTANSandFLOWERING LOCUS Tto regulate flowering in Arabidopsis

Abstract

Summary Day length and ambient temperature are major stimuli controlling flowering time. To understand flowering mechanisms in more natural conditions, we explored the effect of daily light and temperature changes on Arabidopsis thaliana.Seedlings were exposed to different day/night temperature and day-length treatments to assess expression changes in flowering genes.Cooler temperature treatments increased CONSTANS (CO) transcript levels at night. Nighttime CO induction was diminished in flowering bhlh (fbh)-quadruple mutants. FLOWERING LOCUS T (FT) transcript levels were reduced at dusk, but increased at the end of cooler nights. The dusk suppression, which was alleviated in short vegetative phase (svp) mutants, occurred particularly in younger seedlings, while the increase during the night continued over 2 wk. Cooler temperature treatments altered the levels of FLOWERING LOCUS M-β (FLM-β) and FLM-δ splice variants. FT levels correlated strongly with flowering time across treatments.Day/night temperature changes modulate photoperiodic flowering by changing FT accumulation patterns. Cooler nighttime temperatures enhance FBH-dependent induction of CO and consequently increase CO protein. When plants are young, cooler temperatures suppress FT at dusk through SVP function, perhaps to suppress precocious flowering. Our results suggest day length and diurnal temperature changes combine to modulate FT and flowering time.

TOC1–PIF4 interaction mediates the circadian gating of thermoresponsive growth in Arabidopsis

“…Although night temperature can affect plant growth and metabolism, influencing phenotypes such as flowering and fruit development3435, adaptive responses to day temperature could be important for survival of heat stress, as the hottest temperature usually occurs around noon to early afternoon and heat is more detrimental to plants under light than in the dark due to photo-oxidative damage36. Thus, the TOC1-mediated timing of PIF4 activation by daytime warm temperature could potentially be important for thermo-adaptation and survival of heat stresses in nature.…”

The Effect of Fluctuations in Photoperiod and Ambient Temperature on the Timing of Flowering: Time to Move on Natural Environmental Conditions

“…This alteration is closely correlated with the robust enhancement of CO transcription by FBH proteins and a subsequent increase in CO protein abundance during the cooler night. Moreover, the SVP protein functions to repress FT expression at dusk under these conditions, without changing the protein amount (Kinmonth-Schultz et al, 2016) (Fig. 2).…”

“…Thus, importantly, the effect of temperature fluctuations on flowering appears to be substantially photoperiod-dependent (Fig. 2) (Burghardt et al, 2016; Kinmonth-Schultz et al, 2016). The gene expression profile of FT is markedly influenced by warmer day/cooler night cycles in long days but not in short days (Kinmonth-Schultz et al, 2016).…”

“…2) (Burghardt et al, 2016; Kinmonth-Schultz et al, 2016). The gene expression profile of FT is markedly influenced by warmer day/cooler night cycles in long days but not in short days (Kinmonth-Schultz et al, 2016). FT abundance is reduced at dusk but increases at night.…”

Ambient temperature‐directed flowering time regulation : the role of alternative splicing

“…However, in nature, plants are exposed to considerable temperature fluctuations and temperature differences between days and nights. The importance of taking these temperature oscillations into account is illustrated by a recent study that shows that cool night-time temperatures induces FT expression, likely through SVP and FLMδ (Kinmonth-Schultz et al, 2016). The authors demonstrated that under a temperature regime of 22°/12° C (day/night, long day light conditions), SVP levels remained higher after dusk and into the night.…”