Transcription factor HSFA7b facilities thermomemory - induced alternative splicing in Arabidopsis shoot apex by directly modulating the expression of splicing regulator

Alternative splicing (AS) is a crucial adaptive strategy employed by plants to cope with continuously changing environments. In this study, we investigated the mechanistic basis of AS in response to thermomemory at the shoot apex of Arabidopsis thaliana. Our findings revealed that priming heat stress (HS) induces significant alterations in the plant's splicing system leading to a differential heat-induced AS response between previously primed plants and those exposed solely to triggering HS. We found that HEAT SHOCK FACTOR A7b (HSFA7b) undergoes AS only in non-primed plants after reoccurring HS and that the triggering-induced HSFA7b-II variant is targeted for degradation via nonsense-mediated decay. Importantly, we found that functional HSFA7b protein is required to reset the HS-induced AS events, as it directly regulates the expression of key splicing regulators, including ARGININE/SERINE-RICH SPLICING FACTOR 40 (RS40). Ultimately, this research enhances our understanding of the molecular mechanisms facilitating plant adaptation to recurring heat stress.