Abstract: Global warming imposes a major threat to plant survival by disrupting growth homeostasis, yet plants adapt to elevated temperatures through thermomorphogenesis. Although auxin signaling is known to orchestrate these adaptive responses, how temperature perception is integrated with auxin remains poorly understood. Here, we identify the CrRLK1L-family receptor kinase FERONIA (FER) as a central regulator of thermomorphogenesis in Arabidopsis thaliana. Under warm-temperature conditions, FER undergoes proteolytic cleavage, releasing its cytosolic domain FERCD, which translocates into the nucleus via an importin-dependent pathway. Once in the nucleus, FER^CD phosphorylates the non-canonical AUX/IAA protein IAA29, thereby relieving its inhibition of ARF19 and promoting hypocotyl elongation. Transcriptomic analyses further reveal that FER and ARF19 co-regulate thermo-inducible genes involved in auxin signaling and cell wall remodeling. Together, these findings uncover the mechanism by which FER integrates thermal cues through proteolytic activation and phosphorylation-dependent modulation of auxin signaling, establishing a new paradigm for receptor kinase-mediated environmental adaptation in plants.

Key words: auxin, FERONIA, hypocotyl elongation, IAA29, nuclear translocation, thermomorphogenesis