H3K27me3 demethylases regulate flowering time response to low ambient temperature

Flowering time is an important crop trait, as premature or delayed flowering can significantly reduce yields. Plants flower in response to a defined set of endogenous and environmental cues. The effect of ambient temperature on flowering time is extensively studied, but the role of epigenetic modifiers on the floral thermosensory pathway remains largely unexplored. Here we describe that the histone demethylases EARLY FLOWERING 6 (ELF6) and JUMONJI 13 (JMJ13) fine-tune temperature-dependent flowering. We found that the elf6-3 jmj13-1 double mutant is hyposensitive to the effect of low ambient temperature on flowering time. Genetic analyses demonstrate that ELF6 and JMJ13 function requires the cold-responsive floral repressors FLOWERING LOCUS C (FLC) and FLOWERING LOCUS M (FLM). ELF6 and JMJ13 bind to the chromatin of FLC and FLM loci at both temperature regimes, with increased binding to FLM observed at low ambient temperatures. Interestingly, we also detected increased levels of H3 lysine 27 trimethylation (H3K27me3) in the elf6-3 jmj13-1 double mutant at low ambient temperature in FLC and FLM. Our work demonstrates that ELF6 and JMJ13 are required to modulate FLC and FLM gene expression in response to ambient temperature fluctuations, revealing H3K27me3 demethylases as novel players in the floral thermosensory pathway.