Comparative transcriptomic and epigenetic analyses reveal conserved and divergent regulatory pathways in barley response to temperature stresses

DNA methylation and histone modification enable plants to rapidly adapt to adverse temperature stresses, including low temperature (LT) and high temperature (HT) stress. In this study, we conducted physiological, epigenetic, and transcriptomic analyses of barley seedlings grown under control (22 degrees C), mild low temperature (MLT, 14 degrees C) and HT (38 degrees C) conditions to elucidate the underlying molecular mechanisms. Compared to MLT, HT implies greater deleterious effects on barley seedlings' growth. The methylation-sensitive amplification polymorphism analysis showed that MLT induced more DNA methylation and HT more DNA demethylation compared to control. Besides, the higher levels of H3K9ac and H3K4me3 under HT compared to MLT stresses might lead to the loosening of chromatin and, subsequently, the activation of gene expression. Consistently, the transcriptome analysis revealed that there were more differentially expressed genes (DEGs) in plants subjected to HT stress than MLT stress compared to control. The common and unique pathways of these DEGs between MLT and HT were also analyzed. Transcription factors, such as ERF, bHLH, NAC, HSF, and MYB, were most involved in MLT and HT stress. The underlying gene regulation networks of epigenetic modulation-related genes were further explored by weight gene co-expression network analysis. Our study provides new insights into the understanding of epigenetic regulation responses to temperature stress in barley, which will lead to improved strategies for the development of cold- and heat-tolerant barley varieties for sustainable barley production in a climate-changing world.