背景回顾：Heterosis is extensively used to improve crop productivity, yet its allelic and chromatin regulation remains unclear. 

主要发现：Based on our resolved genomes of the maternal TGY and paternal HD, we analyzed the contribution of allele-specific expression (ASE) and chromatin accessibility of JGY and HGY, the artificial hybrids of oolong tea with the largest cultivated area in China.  

结果1-ASEG：The ASE genes (ASEGs) of tea hybrids with maternal-biased were mainly related to the energy and terpenoid metabolism pathways, whereas the ASEGs with paternal-biased tend to be enriched in glutathione metabolism, and these parental bias of hybrids may coordinate and lead to the acquisition of heterosis in more biological pathways. 

结果2-ACR：ATAC-seq results showed that hybrids have significantly higher accessible chromatin regions (ACRs) compared to their parents, which may confer broader and stronger transcriptional activity of genes in hybrids. The number of ACRs with significantly increased accessibility in hybrids was much greater than decreased, and the associated alleles were also affected by differential ACRs across different parents, suggesting enhanced positive chromatin regulation and potential genetic effects in hybrids. 

结果3-ASEG与ACR：Core ASEGs of terpene and purine alkaloid metabolism pathways with significant positive heterosis have greater chromatin accessibility in hybrids and were potentially regulated by several members of the MYB, DOF, and TRB families. The binding motif of CsMYB85 in the promoter ACR of the rate-limiting enzyme CsDXS was verified by DAP-seq. 

结论：These results suggest that higher numbers and more accessible ACRs in hybrids contribute to the regulation of ASEGs, thereby affecting the formation of heterotic metabolites.

IGV browser views showing the three representative accessibility-increasing ACRs in ASEGs on MVA and MEP pathways of tea hybrids.

杂种优势常被用来提升作物产量，然而等位基因及染色质调控对杂种优势的影响仍不清楚。基于前期破译的母本TGY和父本HD的基因组，作者分析了中国种植面积最广的人工杂种乌龙茶中JGY和HGY的等位基因特异性表达（ASE）和染色质可及性。乌龙茶等位基因特异性表达基因（ASEGs）中母本偏性的主要与能量和萜类代谢通路有关，而父本偏性相关的主要富集于谷胱甘肽代谢；杂种的这些亲本偏性可能相互协调，并在更多的生物学途径中获得杂种优势。ATAC-seq结果显示，与亲本相比，杂种具有明显更高的染色质可及区域（ACRs），这可能导致杂种具有比亲本更广和更强的转录活性。杂种中染色质可及性增强的ACR的数量要远比减弱的多，并且相关的等位基因受到不同亲本不同ACRs的影响，揭示了杂种中增强的正向染色质调控和潜在的遗传效应。杂种中具有显著正向杂种优势的萜烯和嘌呤生物碱代谢通路核心ASEGs具有更高的染色质可及性，并且这些染色质可及区域存在MYB、DOF和TRB等转录因子的潜在结合位点。作者进一步通过DAP-seq验证了限速酶编码基因CsDXS启动子上ACR存在CsMYB85的结合基序。本文的研究结果表明，杂种中更多和更可及的ACRs作用于ASEGs的转录调控，从而影响杂种优势代谢物的形成。

** 张兴坦 **