PT - JOURNAL ARTICLE AU - Maximilian O. Press AU - Amy Lanctot AU - Christine Queitsch TI - ELF3 polyQ variation in <em>Arabidopsis thaliana</em> reveals a PIF4-independent role in thermoresponsive flowering AID - 10.1101/038257 DP - 2016 Jan 01 TA - bioRxiv PG - 038257 4099 - http://biorxiv.org/content/early/2016/03/22/038257.short 4100 - http://biorxiv.org/content/early/2016/03/22/038257.full AB - Plants have evolved elaborate mechanisms controlling developmental responses to environmental stimuli. A particularly important stimulus is temperature. Previous work has identified the interplay of PIF4 and ELF3 as a central circuit underlying thermal responses in Arabidopsis thaliana. However, thermal responses vary widely among strains, possibly offering mechanistic insights into the wiring of this circuit. ELF3 contains a polyglutamine (polyQ) tract that is crucial for ELF3 function and varies in length across strains. Here, we use transgenic analysis to test the hypothesis that natural polyQ variation in ELF3 is associated with the observed natural variation in thermomorphogenesis. We found little evidence that the polyQ tract plays a specific role in thermal responses beyond modulating general ELF3 function. Instead, we made the serendipitous discovery that ELF3 plays a crucial, PIF4-independent role in thermoresponsive flowering under conditions more likely to reflect field conditions. We present evidence that ELF3 acts through the photoperiodic pathway, pointing to a previously unknown symmetry between low and high ambient temperature responses. Moreover, in analyzing two strain backgrounds with vastly different thermal responses, we demonstrate that responses may be shifted rather than fundamentally rewired across strains. Our findings tie together disparate observations into a coherent framework in which multiple pathways converge in accelerating flowering in response to temperature, with some such pathways modulated by photoperiod.AUTHOR SUMMARY Understanding plant responses to elevated temperature is crucial in a warming world that threatens crop yields. Previous work suggested that the protein PIF4 is a master regulator of early flowering at elevated temperatures in short days typical of temperate cold seasons. However, short days are not usually paired with elevated temperatures in the field. We show that the protein ELF3 is essential for thermoresponsive early flowering in the more realistic scenario of long days. We further demonstrate that this role is independent of PIF4. Our study suggests that several pathways are important for thermoresponsive flowering, with some (like PIF4) operating only under certain day lengths.