小叶杨耐高温逆境胁迫特性形成的表观转录调控机制

DNA methylation plays important roles in responses to environmental stimuli. However, in perennial plants, the roles of DNA methylation in stress-specific adaptions to high temperature stresses remain unclear. To analysis the epigenetics mechanism of perennial woody plants respond to high temperature stress under global warming and frequent extreme high temperature weather. Here, we use 642 individuals of germplasm populations from P. simonii to systematically launch several research topics as follows: 1) Analysis of characteristics of P. simonii population in response to high temperature stress. Evaluation and selection of poplar clones resistance to high temperature; 2) Transcript regulation mechanism of high temperature responsive genes splicing and allelic imbalance expression; 3) Analysis of DNA methylation genetic transcription regulatory mechanism using high-efficiency CRISPR-dCas9 technology. Therefore, our study could reveal characteristics of P. simonii population in response to high temperature stress, evaluate excellent clones resistance to high temperature and dissect the transcription regulation function of DNA methylation on high temperature responsive genes. This work will provide innovative achievements, which have theoretical and practical values, on solving the significant theoretical and technical matters in poplar breeding for stress tolerance and research on molecular mechanism on the formation of adverse-resistant characteristics of perennial woody plants.

在全球变暖、极端高温天气频发的背景下，精确解析林木耐高温逆境胁迫特性形成的表观转录调控机制是决定耐高温分子育种研究能否有效开展的关键环节。本项目以小叶杨全国优异种质资源群体中642株个体为材料，系统开展（1）全国小叶杨种质资源高温逆境胁迫下生理生化响应的群体特性及耐高温优良无性系筛选；（2）高温胁迫响应基因可变剪切与等位基因不平衡表达的表观调控模式解析；（3）DNA甲基化在转录调控过程中的分子生物学功能研究。通过本项目的实施，将揭示小叶杨响应高温胁迫生理生化群体遗传变异规律，结合DNA甲基化对于高温胁迫响应基因可变剪切及等位基因表达的转录调控作用的解析，为进一步阐明林木抗逆特性形成的分子机理提供理论基础，为小叶杨耐高温优良无性系选育提供技术支持，具有重要的科学意义。

在全球变暖、极端高温天气频发的背景下，精确解析林木耐高温逆境胁迫特性形成的表观转录调控机制是决定耐高温分子育种研究能否有效开展的关键环节。本项目以小叶杨全国优异种质资源群体为材料，系统地开展了小叶杨群体高温胁迫响应生理指标遗传多样性剖析工作。在此基础上，筛选了6个小叶杨抗高温胁迫优良无性系，明确了小叶杨抗逆优良无性系高温胁迫下塑性胁变产生的临界点，联合利用Bisulfite-seq、RNA-seq、ISO-seq等高通量测序方法对DNA甲基化对等位基因表达以及可变剪切的转录调控关系进行了系统地解析，建立了小叶杨高温胁迫响应表观转录调控网络。利用CRISPR-dCas9技术，实现了杨树基因组定点甲基化修饰，解析了DNA甲基化修饰对不同转录本表达水平的调控作用。阐明了高温胁迫下PsiXBAT32第二外显子侧翼序列MITE及其互补配对序列的DNA甲基化含量显著下降，顺式调控PsiXBAT32第二外显子环化形成CircRNA-0003418。在高温胁迫下，CircRNA-0003418的上调表达导致PsiXBAT32.5转录本丰度上调，PsiXBAT32.3转录本丰度下降。PsiXBAT32.5转录本由于缺失E3连接酶结构域，丧失泛素化功能，负调控乙烯合成的作用消失，最终导致乙烯大量产生，降低了杨树高温胁迫下的生长量与存活率。本研究揭示了小叶杨响应高温胁迫生理生化群体遗传变异规律，结合DNA甲基化对于高温胁迫响应基因可变剪切及等位基因表达的转录调控作用的解析，为进一步阐明林木抗逆特性形成的分子机理提供理论基础，为小叶杨耐高温优良无性系选育的亲本选配提供了技术支撑，具有重要的科学意义。