Rice Chromatin Protein OsHMGB1 Is a Transcriptional Facilitator that Regulates Phosphate Homeostasis and Plant Growth [ChIP-seq]

Although phosphorus is one of the most important essential elements for plant growth and development, the epigenetic regulation of inorganic phosphate (Pi) signaling is poorly understood. In this study, we identified the high-mobility-group protein OsHMGB1 as a key regulator of phosphate homeostasis and plant growth in rice (Oryza sativa). OsHMGB1 expression is induced by Pi starvation and encodes a nucleus-localized protein. Relative to wild-type plants, Oshmgb1 mutant plants had lower Pi content in their leaves, whereas plants overexpressing OsHMGB1 had higher Pi content, indicating that OsHMGB1 positively regulates Pi accumulation. Transcriptome deep sequencing and chromatin immunoprecipitation followed by sequencing showed that OsHMGB1 regulated the expression of a series of phosphate starvation responsive (PSR) genes by binding to their promoters. Furthermore, Assay for Transposase-Accessible Chromatin followed by sequencing revealed that OsHMGB1 was involved in maintaining chromatin accessibility. Indeed, OsHMGB1 occupancy positively correlated with genome-wide chromatin accessibility and gene expression levels. Notably, we determined that OsHMGB1 interacted with RNA polymerase II to help regulate transcription, especially under low Pi conditions. Taken together, our results suggest that OsHMGB1 functions as a transcriptional facilitator, revealing a key epigenetic mechanism to regulate Pi homeostasis and fine-tune plant acclimation responses to Pi-limited environments. Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) for HMG-GFP transgenic plants Overall design: Yan,Wang

尽管磷是植物生长发育过程中至关重要的必需元素之一，但目前针对无机磷酸盐（inorganic phosphate, Pi）信号通路的表观遗传调控机制仍知之甚少。本研究中，我们鉴定出高迁移率族蛋白OsHMGB1作为水稻（Oryza sativa）中磷酸盐稳态与植物生长的关键调控因子。OsHMGB1的表达受磷饥饿诱导，且其编码的蛋白定位于细胞核。与野生型植株相比，Oshmgb1突变体植株的叶片中Pi含量更低，而过表达OsHMGB1的植株则具有更高的Pi含量，这表明OsHMGB1可正向调控Pi的积累。深度转录组测序与染色质免疫共沉淀DNA测序（ChIP-seq）结果显示，OsHMGB1可通过结合一系列磷饥饿响应（phosphate starvation responsive, PSR）基因的启动子来调控其表达。此外，转座酶可及性测序（assay for transposase-accessible chromatin followed by sequencing, ATAC-seq）分析揭示，OsHMGB1参与维持染色质可及性。确实，OsHMGB1的基因组结合占据度与全基因组范围内的染色质可及性及基因表达水平呈正相关。值得注意的是，我们发现OsHMGB1可与RNA聚合酶II（RNA polymerase II）相互作用，以协助调控转录过程，尤其在低磷条件下。综上，我们的研究结果表明，OsHMGB1作为一种转录促进因子发挥功能，揭示了调控磷酸盐稳态并微调植物对低磷环境的适应响应的关键表观遗传机制。针对HMG-GFP转基因植株的染色质免疫共沉淀DNA测序（ChIP-seq）实验 整体设计：Yan、Wang