Sorghum bicolor is a C4 plant with the characteristics of high stress tolerance. In this study, we investigated the differential enrichment of 7 histone marks in leaf and root as well as in response to PEG treatment in the two organs, and revealed some epigenomic features that have never been reported before. For example, the long H3K27me3 regions clustered in four areas, which we defined as H3K27me3 islands, were identified in sorghum. The increase of some H3K27me3 enrichment was associated with gene up-regulation in leaf but not in root. H3K36me3 plays some role in inhibiting the deposition of both H3K27me3 and H2A.Z, which may serve as partial motivation for the removal of H3K27me3 and H2A.Z in leaf and root, but was not involved in the prevention of H3K27me3 spreading into a long region. Finally, we analyzed histone mark variation in the genes that were differentially expressed both between leaf and root and in response to PEG treatment (defined as common DEGs), and found that most of the changes of histone marks occurred in some common DEGs in leaf and root could not be observed in the same genes in response to PEG treatment.
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