Introduction

Nucleosomes harboring specific histone variants show distinct chromatin localization patterns and regulatory functions, thereby playing crucial roles in epigenetic regulation. Compared to the well-understood variants of H2A and H3, the study about H2B variants is emerging. Deciphering the roles and regulatory mechanisms of H2B variants in plants will provide more knowledges about epigenetic regulations in plant biology.

Objectives

Using the model plant Arabidopsis thaliana as the research subject, we systematically analyzed histone H2B variants, four short N-terminal histone H2B variants (snH2Bs) were identified. The genomic distribution characteristics of these snH2Bs, their impact on plant growth, and the potential regulatory mechanisms were studied.

Methods

By integrating whole-genome chromatin immunoprecipitation sequencing (ChIP-seq) and fluorescence microscopy localization analysis, the distribution of snH2Bs across the genome was identified. Single, double, and triple knock-out mutants were constructed using CRISPR-Cas9 to further explore the functions of snH2Bs in the growth process of Arabidopsis thaliana, the possible mechanisms were also discussed.

Results

These snH2B variants are preferentially expressed in reproductive tissues and are detected in the nuclei of pollen grains. Further genome-wide profiling indicates that the snH2Bs distribute at active chromatin regions and are positively correlated with gene expression. By creating knock-out single, double, and triple mutants for these snH2Bs, we demonstrate that H2B.5 influences vegetative to reproductive transition. We also show that H2B.5 is required for proper accumulation of H3 lysine 9 acetylation and H2B mono-ubiquitination.

Conclusion

Overall, our study not only provide insights into the functions and chromatin characteristics of plant snH2Bs, but also supplies examples that illustrate the interplay between histone variants and histone modification. These findings contribute to the understanding of the fundamental principles of epigenetic regulation in eukaryotes and also highlight potential targets for crop improvement.

中文翻译：

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拟南芥中短 N 端 H2B 变异的全基因组分析和功能研究

 介绍

携带特异性组蛋白变体的核小体显示出不同的染色质定位模式和调节功能，从而在表观遗传调控中起关键作用。与众所周知的 H2A 和 H3 变体相比，关于 H2B 变体的研究正在出现。破译植物中 H2B 变异的作用和调控机制将为植物生物学中的表观遗传调控提供更多知识。

 目标

以模式植物拟南芥为研究对象，系统分析组蛋白 H2B 变体，鉴定出 4 个短 N 末端组蛋白 H2B 变体 （snH2B）。研究了这些 snH2B 的基因组分布特征、它们对植物生长的影响以及潜在的调控机制。

 方法

通过整合全基因组染色质免疫沉淀测序 （ChIP-seq） 和荧光显微镜定位分析，确定了 snH2B 在基因组中的分布。使用 CRISPR-Cas9 构建单、双和三重敲除突变体，以进一步探索 snH2B 在拟南芥生长过程中的功能，并讨论了可能的机制。

 结果

这些 snH2B 变体优先在生殖组织中表达，并在花粉粒的细胞核中检测到。进一步的全基因组分析表明，snH2B 分布在活性染色质区域，并与基因表达呈正相关。通过为这些 snH2B 创建敲除单、双和三重突变体，我们证明了 H2B.5 影响营养到生殖的转变。我们还表明 H2B.5 是 H3 赖氨酸 9 乙酰化和 H2B 单泛素化正确积累所必需的。

 结论

总体而言，我们的研究不仅提供了对植物 snH2B 的功能和染色质特征的见解，还提供了说明组蛋白变体和组蛋白修饰之间相互作用的示例。这些发现有助于理解真核生物表观遗传调控的基本原理，也突出了作物改良的潜在目标。