Transcriptomic analysis of reduced thermotolerance in Arabidopsis seedlings lacking the metacaspase AtMC1

More frequent short-term episodes of extreme high temperatures caused by global warming seriously threaten plant growth and development around the world. Although heat stress can occur throughout the plant life cycle, exposure during the seedling stage severely impacts subsequent plant growth and productivity. In this study, we found that the Arabidopsis metacaspase mutant atmc1 exhibited a heat-sensitive phenotype at the seedling stage, and restoration of AtMC1 expression in the atmc1 substantially rescued the heat-sensitive phenotype, indicating an important role of AtMC1 in thermotolerance. To investigate the underlying molecular responses associated with AtMC1 under heat stress, RNA sequencing was performed to compare the transcriptomic profiles of wild-type and atmc1 seedlings under normal and heat treatment conditions. Gene set enrichment analysis (GSEA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses identified key genes related to heat acclimation, protein folding, and endoplasmic reticulum-associated degradation (ERAD). Genes involved in reactive oxygen species (ROS) homeostasis also displayed differential expression patterns under heat stress. In addition, 45 transcription factors belonging to the ERF, HSF, WRKY, NAC, and MYB families were differentially expressed between wild-type and atmc1 in response to heat stress. Protein-protein interaction analysis revealed 27 key heat-responsive genes, most of which were heat-induced but exhibited attenuated upregulation in atmc1. Collectively, our findings provide transcriptomic insights into the heat stress responses associated with loss of AtMC1 in Arabidopsis seedlings and provide a foundation for future mechanistic studies of AtMC1-mediated thermotolerance.