ABSTRACT: In Arabidopsis, ELF3, ELF4 and LUX proteins form the EC complex. The EC complex binds directly to the promoters of PIF4 and PIF5 in vivo, thereby inhibiting PIF4 and PIF5 expression at night. PIF4, as a key transcription factor for light and temperature, binds to thousands of target genes to regulate their expression. High temperature can activate PIF4 activity, making it regulate plant thermal morphogenesis by integrating light, circadian rhythm and hormone signals, EC complex is a protein complex that inhibits gene expression, and helps higher plants sense environmental temperature and thermal form. ELF3 is a thermal sensor that plays a role in controlling the circadian rhythm, photoperiodic flowering, hypocotyl length, and response to light in an EC-dependent and EC-independent manner. PIF4 plays a key positive role in heat response gene expression and hypocotyl growth in Arabidopsis thaliana, but ELF3 negatively regulates the protein activity of growth promoting factor PIF4. Interestingly, a 2020 paper published in Nature by Jung et al. found that ELF3, as a heat sensor, gradually forms multiple distinct spot-like structures in the nucleus as the temperature increases due to the presence of the characteristic PrD. Similarly, increasing the length of the polyQ will enlarge the spots. In addition, after returning to normal temperature from mild high temperature, the EC complex will quickly return to normal activity. This result is contrary to what Ronald et al. stated in a 2021 paper: Warm temperatures inhibit ELF3 blotching, and since ELF3 blotching is associated with increased transcriptional activity of ELF3, a decrease in blotching may lead to decreased EC function at warm temperatures. As a result, the question of how ELF3 is regulated in warmer temperatures remains an open question.
