Whole-genome analysis of the trimethylation of histone H3 lysine 4 and lysine 27 in two contrasting Tibetan hulless barley genotypes under salinity stress

One of the major abiotic stresses with great influence on plant growth and development and contributing to severe damage to the yield of Tibetan hulless barley is salinity. Elucidating the channels of retaliation to salinity is important in breeding salt-tolerant hulless barley varieties. Genome-wide examination of histone H3 lysine 4 and lysine 27 trimethylation (H3K4me3, H3K27me3) was conducted in salt-tolerant hulless barley Z0119 and salt-sensitive hulless barley Z0226. We found that the profile of genes with both histone H3 lysine 4 and lysine 27 methylation showed specific and contrasting changes in Z0119 at 24 h and 72 h as compared to Z0226. In Z0119, genes affiliated to oxidative processes were significantly elevated, while in Z0226, enrichment of the genes entailed in the affair of protein complex assembly was observed. Considering the similar trends in malondialdehyde concentration and catalase activity in Z0119, co-localization of H3K4me3 with H3K27me3 might have activated defense against the oxidative stress and improve its salinity tolerance. Furthermore, salt-related genes were selected in rice, and the homology of these genes in hulless barley were both found to carries modifications, such as HVUL5H46981.2 and HVUL1H09481.2. Identical pattern change was observed in the execution levels and histone refinement extent of the two genes described above. This indicated that H3K4me3 and H3K27me3 refinement coordinates to regulate gene execution and quickly respond to environmental stimuli. Taken together, these results help to unravel the duty of epigenetic refinement in plant reaction to salt-stress situations.