H3K4me3 and H3K9ac Histone Modifications and Leaf Aging in Arabidopsis thaliana

H3K4me3 and H3K9ac histone marks and gene expression were respectively monitored by ChIP-seq and RNA-seq in aging Arabidopsis thaliana rosette leaves. Both of these activating marks coincided at all stages of leaf aging with twice the area covered by H3K4me3 marks compared to H3K9ac marks. The breadth of gene coverage positively correlated with gene expression during plant aging. H3K4me3 and H3K9ac marks were present before a large induction of mRNA for most genes up-regulated during senescence. However, for a subset of genes, the respective gain or loss of H3K4me3 marks were found to closely match the temporal changes in mRNA abundance. Although approximately 15% of genes show accompanying changes in H3K4me3 modification and gene expression, they may act as primary response genes since numerous regulatory genes are included in this subset.