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Genome-wide analysis of drought stress induced histone 3 lysine 4 and histone 3 lysine 27 trimethylation modifications in winter wheat

Liao, Chi-Ping

Drought stress brings great impact on plant growth and development, that it is the most critical threat to world food security. Although drought responsive mechanisms plants have developed to tolerate drought stress are relatively well known, the studies of genome-wide histone modifications induced by drought or other abiotic stresses is still fragmentary. In this study, I used whole-genome ChIP-seq to study genome-wide active histone mark, histone H3 lysine 4 trimethylation (H3K4me3), and repressive histone mark, histone H3 lysine 27 trimethylation (H3K27me3) patterns in winter wheat under drought stress. I found that although similar patterns of chromosomal and genomic distributions in both WW and DT were seen, the number of genes modified by H3K4me3 mark was increased and by H3K27me3 mark was reduced under drought condition. In addition, a good portion of genes was newly modified after drought treatment, especially for H3K4me3 modification. About 43% of DT H3K4me3 marked genes were unique to drought condition, and over half of these drought-specific genes were significantly enriched with H3K4me3 in DT. Surprisingly, I identified 3,819 bivalent genes in DT, and the bivalency of over 70% of these bivalent genes was established upon water deficit. Interestingly, these newly formed bivalent genes in DT were established by depleting the repressive marks and obtaining the active marks, whereas the levels of bivalency did not change in the bivalent genes which were common in WW and DT. These results suggested that drought stress induced H3K4me3 modifications and reduced the modifications of H3K27me3, and further to enhance bivalency during drought treatment in winter wheat.