英国约翰英纳斯中心冯小琦等研究人员合作发现，组蛋白H2B.8通过染色质相分离压实开花植物的精子。这一研究成果于2022年11月2日在线发表在国际学术期刊《自然》上。

研究人员发现，在拟南芥中，一个组蛋白变体（H2B.8）介导了精子染色质和核浓缩。H2B.8的缺失导致精子核增大、染色质分散，而体细胞中的异位表达则产生较小的核、染色质浓缩。这一结果表明，H2B.8对染色质的浓缩是足够的。H2B.8将转录不活跃的富含AT的染色质聚集成相分离的浓缩物，这有利于核的压实而不减少转录。互换杂交显示，h2b.8的突变会减少雄性的传递，这表明H2B.8介导的精子压实对生育力很重要。

总的来说，这些研究结果揭示了一种通过未表达染色质的全局浓缩进行核压实的新机制。研究人员提出，H2B.8是开花植物的一种演化创新，它实现了与主动转录相适应的核压缩。

据介绍，精子染色质通常被精蛋白转化为紧凑和转录不活跃的状态。开花植物的精子细胞缺乏精蛋白，但它们有小的、转录活跃的细胞核，其染色质通过一种未知的机制浓缩。

附：英文原文

Title: Histone H2B.8 compacts flowering plant sperm through chromatin phase separation

Author: Buttress, Toby, He, Shengbo, Wang, Liang, Zhou, Shaoli, Saalbach, Gerhard, Vickers, Martin, Li, Guohong, Li, Pilong, Feng, Xiaoqi

Issue&Volume: 2022-11-02

Abstract: Sperm chromatin is typically transformed by protamines into a compact and transcriptionally inactive state1,2. Sperm cells of flowering plants lack protamines, yet they have small, transcriptionally active nuclei with chromatin condensed through an unknown mechanism3,4. Here we show that a histone variant, H2B.8, mediates sperm chromatin and nuclear condensation in Arabidopsis thaliana. Loss of H2B.8 causes enlarged sperm nuclei with dispersed chromatin, whereas ectopic expression in somatic cells produces smaller nuclei with aggregated chromatin. This result demonstrates that H2B.8 is sufficient for chromatin condensation. H2B.8 aggregates transcriptionally inactive AT-rich chromatin into phase-separated condensates, which facilitates nuclear compaction without reducing transcription. Reciprocal crosses show that mutation of h2b.8 reduces male transmission, which suggests that H2B.8-mediated sperm compaction is important for fertility. Altogether, our results reveal a new mechanism of nuclear compaction through global aggregation of unexpressed chromatin. We propose that H2B.8 is an evolutionary innovation of flowering plants that achieves nuclear condensation compatible with active transcription.

DOI: 10.1038/s41586-022-05386-6

Source: https://www.nature.com/articles/s41586-022-05386-6