Fig. 5.

Simplified model of ambient temperature signaling. ELF3 functions as a transcriptional repressor of PIF4 and integrates temperature and photoperiod information in the regulation of thermomorphogenesis. In addition, PIF4 regulation in response to temperature involves the regulatory components of the photomorphogenesis pathway DET1, COP1, and HY5 [10]. PIF4-mediated transcriptional regulation of target genes can be terminated by the RNA binding protein FCA, causing dissociation of PIF4 from target gene promoters [33]. Additional mechanisms previously shown to contribute to PIF4 regulation e.g., transcriptional regulation of target genes via the BAP/HLH/bHLH module of transcription factors [34]. might contribute also to the regulation of temperature responses. Other putatively involved modulators of PIF4 activity known from other biological contexts are depicted by gray dashed lines. These involve direct binding of DET1 to PIF4 [12], competition of PIF4 and other transcription factors for similar binding sites [35], PIF4 protein sequestration by HFR1 [36] and phyB-mediated phosphorylation and degradation of PIF4 [37]