BioProject

Histone modifications regulate gene expression in eukaryotes, but their roles in gene expression changes in interspecific hybrids or allotetraploids are poorly understood. More...

Histone modifications regulate gene expression in eukaryotes, but their roles in gene expression changes in interspecific hybrids or allotetraploids are poorly understood. Histone modifications can be mapped by immunostaining of metaphase chromosomes at the single cell level and/or by chromatin immunoprecipitation-sequencing (ChIP-seq) for individual genes. Here we examined H3K4me3 density and transcriptome maps in root-tip cells of allotetraploid cotton (Gossypium hirsutum L.). The overall H3K4me3 levels were relatively equal between A and D chromosomes, which were consistent with equal numbers of expressed genes between the two subgenomes. However, intensities per chromosomal area were nearly twice as high in the D homoeologs as in the A homoeologs. Consistent with the cytological observation, ChIP-seq analysis showed more D-homoeologs with biased H3K4me3 levels than A-homoeologs with biased modifications, which correlated with the greater number of genes with D-biased expression than that with A-biased expression in most homoeologous chromosome pairs. Two chromosomes displayed different expression levels compared with other chromosomes probably because of translocations, which may affect the local chromatin structure (hence expression levels) for the genes involved. This example of genome-wide histone modifications that determine expression bias of homoeologous genes in allopolyploids provides a molecular basis for the evolution and domestication of polyploid species including important crops. Overall design: RNA-seq analysis using sequence libraries prepared from the root tip, which was the same tissue used to prepare for metaphase chromosome immune-staining assays. Three independent mRNA-seq libraries were constructed and sequenced by Illumina paired-end reads. Less...