An amino acid of the thermosensor EARLY FLOWERING 3 regulates temperature flexibility in <i>Arabidopsis</i>

Temperature is a vital environmental signal that influences plant growth and development. The evening complex (EC) component EARLY FLOWERING 3 (ELF3) functions as a proposed thermosensor that senses high temperatures via its prion-like domain (PrD) with a polyglutamine (polyQ) repeat. However, the mechanisms by which ELF3 perceives and deciphers temperature signals require further exploration. Here, we discovered that an amino acid in ELF3 outside of PrD is responsible for detecting temperature oscillations in Arabidopsis (Arabidopsis thaliana). The elf3-16 allele, in which Ser-364 of ELF3 is replaced by Pro, confers high sensitivity to elevated ambient temperature and remolds the expression patterns of ELF3-regulated genes similarly to those of the wild type at low ambient temperature but similarly to those of the elf3 null allele under warm ambient conditions. The mutation in elf3-16 alters the predicted protein conformation and reduces the protein accumulation of ELF3 under normal and warm ambient conditions rather than under cool conditions. We demonstrate that ELF4, another EC member, is essential for the accumulation of ELF3 in response to temperature elevation. The impaired stability of ELF3 in the elf3-16 mutant can be restored by overexpression of ELF4. Thus, our findings reveal a site independent of PrD in ELF3 that controls temperature flexibility in plants.