Transcriptome alterations related to heat stress responses of wild and cultivated barley

Heat stress, exacerbated by global warming, threatens food security by disrupting plant growth and productivity across many regions. The present study compared the transcriptome changes of heat-tolerant wild (Hordeum vulgare ssp. spontaneum L.) genotype and heat-sensitive cultivated Hordeum ('Mona' cultivar) barley subjected to control (24 ± 2 °C) and heat stress (40 ± 2 °C, 3 h) conditions via RNA sequencing with the Illumina Hiseq2500 platform. The wild barley genotype exhibited less impact from heat stress on growth and physiology than the 'Mona' cultivar. Heat stress led to 2141 differentially expressed genes (DEGs) in the heat-tolerant wild genotype and 1456 in the 'Mona' cultivar. Gene ontology enrichment analysis of the DEGs revealed that biological processes such as defense response to heat stress, proline and polyamine biosynthesis, and oxidative stress scavenging were predominantly involved in the thermo-tolerance of wild barley. Moreover, heat shock proteins, osmoprotectants, and catalytic activity were identified as the most critical molecular functions in response to high temperatures in wild barley. The significant alterations in the expression levels of candidate genes in response to heat stress highlight these genes' pivotal role in the thermo-tolerance of wild barley compared to the heat-sensitive 'Mona' cultivar. Comparing the evolved mechanisms in response to high temperatures between wild and cultivated barley helps identify the effective heat tolerance mechanisms in the thermo-tolerant wild genotype.