CNRS, Sorbonne Université, UPMC University Paris 06, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France.
Université de Nantes, CNRS, UFIP, UMR 6286, F-44000, Nantes, France.
Genome Biol. 2021 Jan 4;22(1):12. doi: 10.1186/s13059-020-02216-8.
Brown algae evolved complex multicellularity independently of the animal and land plant lineages and are the third most developmentally complex phylogenetic group on the planet. An understanding of developmental processes in this group is expected to provide important insights into the evolutionary events necessary for the emergence of complex multicellularity. Here, we focus on mechanisms of epigenetic regulation involving post-translational modifications of histone proteins.
A total of 47 histone post-translational modifications are identified, including a novel mark H2AZR38me1, but Ectocarpus lacks both H3K27me3 and the major polycomb complexes. ChIP-seq identifies modifications associated with transcription start sites and gene bodies of active genes and with transposons. H3K79me2 exhibits an unusual pattern, often marking large genomic regions spanning several genes. Transcription start sites of closely spaced, divergently transcribed gene pairs share a common nucleosome-depleted region and exhibit shared histone modification peaks. Overall, patterns of histone modifications are stable through the life cycle. Analysis of histone modifications at generation-biased genes identifies a correlation between the presence of specific chromatin marks and the level of gene expression.
The overview of histone post-translational modifications in the brown alga presented here will provide a foundation for future studies aimed at understanding the role of chromatin modifications in the regulation of brown algal genomes.
褐藻独立于动物和陆地植物谱系进化出了复杂的多细胞性，是地球上第三大发育最复杂的系统发育群。对该类群发育过程的理解有望为阐明复杂多细胞性出现所必需的进化事件提供重要线索。在这里，我们重点关注涉及组蛋白蛋白翻译后修饰的表观遗传调控机制。
共鉴定出 47 种组蛋白翻译后修饰，包括一种新的 H2AZR38me1 标记，但外生褐藻缺乏 H3K27me3 和主要多梳复合物。ChIP-seq 鉴定出与转录起始位点和活性基因及转座子基因体相关的修饰。H3K79me2 呈现出一种不寻常的模式，通常标记跨越几个基因的大基因组区域。紧密间隔、反向转录的基因对的转录起始位点共享一个共同的核小体缺失区域，并表现出共享的组蛋白修饰峰。总体而言，组蛋白修饰模式在整个生命周期中是稳定的。对偏向于有性生殖的基因的组蛋白修饰分析表明，特定染色质标记的存在与基因表达水平之间存在相关性。
本文对面褐藻中组蛋白翻译后修饰的概述将为未来旨在了解染色质修饰在调控褐藻基因组中的作用的研究提供基础。
