Decoding Hormone Signaling Dynamics in Arabidopsis Under Combined Stress: How Different Abiotic Stress Responses Are Fine-Tuned by High Temperatures.

Climate models predict that episodes of extreme heat will intensify in both frequency and severity in the upcoming decades, significantly impacting plant growth, productivity, and survival. In addition, plants in natural environments are often exposed to many other stress factors simultaneously, triggering responses even more complex and difficult to predict. Understanding how plants integrate multiple abiotic stress signals is essential for improving resilience to increasingly complex environmental conditions. In this study, we investigated how heat stress (HS) modulates hormonal signaling networks when occurring in combination with other abiotic stressors. We focused on three specific combinations: salinity and heat (S + HS), water deficit and heat (WD + HS), and high light and heat (HL + HS). Through a comprehensive meta-analysis of publicly available RNA-seq datasets from Arabidopsis thaliana, we assessed the proportion of differentially expressed transcripts associated with major hormone signaling pathways, with particular attention to abscisic acid (ABA) and jasmonic acid (JA). Because transcription factors represent a central layer of stress integration, we also examined the expression pattern of different heat shock factors (HSFs) and analyzed how their activity is potentially associated with hormone responses under each stress combination. Our results reveal that HS substantially alters both ABA and JA responses in a stress-specific manner, amplifying or attenuating hormone dynamics depending on the co-occurring stress. This work highlights the importance of hormonal crosstalk and signal integration in shaping plant responses to stress combinations that include HS and provides a foundation for developing crop improvement strategies aimed at enhancing tolerance to climate change-associated stress combinations.