Cold-dependent ELF6 accumulation drives H3K27me3 demethylation to 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. While the effects of ambient temperature on flowering time are well-studied, the role of epigenetic modifiers in the floral thermosensory pathway remains largely unexplored. Here, we show that the histone demethylases EARLY FLOWERING 6 (ELF6) and JUMONJI 13 (JMJ13) act redundantly to fine-tune temperature-dependent flowering. We found that the elf6-3 jmj13-1 double mutant is hyposensitive to the flowering delay induced by low ambient temperature. Genetic analyses indicated that this response requires FLOWERING LOCUS M ( FLM ) and, to a lesser extent, its homolog FLOWERING LOCUS C ( FLC ). Consistent with these genetic requirements, transcript and chromatin immunoprecipitation (ChIP) analyses revealed that ELF6 and JMJ13 modulate FLM and FLC expression. ChIP assays showed that both proteins associate with FLM and FLC , but with distinct dynamics: JMJ13 exhibited low-level, constitutive occupancy, whereas ELF6 recruitment was temperature and development dependent. Remarkably, ELF6 binding was detected earlier in development under low ambient temperature, coincident with increased ELF6 protein accumulation in germinating seedlings. Together, our data support a model in which low ambient temperature promotes early ELF6 recruitment to limit repressive histone H3 lysine 27 trimethylation (H3K27me3) accumulation at thermoresponsive floral repressors, thereby enabling appropriate gene expression and flowering-time control. These findings identify H3K27me3 demethylases as key components of the floral thermosensory pathway and highlight epigenetic mechanisms linking ambient temperature to flowering.