Transcriptional activity is shaped by the chromatin landscapes in Arabidopsis

Abstract

SummaryHow histone variants and histone modifications shape nucleosome-mediated transcriptional repression, and how transcriptional activity shapes the enrichment of histone modifications and variants remain unclear. To clarify these relationships, we examined chromatin organization in the Arabidopsis thaliana genome, identifying a limited number of chromatin landscapes that distinguish transposon families and distinct groups of genes based on their transcriptional regulation. Unexpectedly, H2A variants are strong determinants of the landscape architecture. Combinations of H2A.W and four histone modifications define six domains that are occupied by specific transposon families and organized concentrically around the centromere. Moreover, H2A.Z defines transcriptional gene repression in specific domains. Expressed genes occupy four chromatin landscapes with specific RNA Polymerase II profiles. Although the composition of each chromatin landscape is invariant, they cover genes with a wide range of expression levels. Therefore, chromatin landscapes control the range of transcriptional activity, but transcriptional activity has little effect on chromatin composition. One Sentence SummaryHistone variants and histone modifications build a limited number of distinct chromatin landscapes that instruct the transcriptional regulation of genes and transposons in Arabidopsis.