植物通过整个抗旱基因网络快速、协调的变化适应干旱胁迫，其中转录因子和表观遗传修饰发挥着关键调控作用。然而，在此过程中表观遗传修饰及其与转录因子相互协调机制还不清楚。本项目前期的研究发现PtrNACs基因表达与H3K9ac水平密切相关，并且转录因子PtrAREB1s可能调控PtrNACs。同时，鉴定出了干旱诱导的组蛋白乙酰化酶复合体基因PtrGCN5-1、PtrADA2b及一个新的可变剪切产物PtrADA2b-α。在此基础上，本项目将研究组蛋白乙酰化酶复合体与PtrAREB1s调控PtrNACs基因H3K9乙酰化激活其表达响应干旱胁迫的分子机制，以及这些基因在毛果杨应答干旱胁迫中的功能，并鉴定PtrNACs调控的靶基因及分析其调节的抗旱代谢途径。该项目的实施将揭示组蛋白修饰H3K9ac与转录因子AREB1协同调控毛果杨响应干旱胁迫的分子机制，为培育高抗林木树种进行遗传改良提供理论基础。

Drought severely affects plant growth and forest productivity. Plants respond and adapt to drought stress through coordinated changes at transcriptional level of drought responsive gene networks. This requires complex transcriptional regulation and a change in chromatin accessibility. However, the molecular connections among these factors and with drought response are not known. Here, we found that the transcriptional activity of PtrNACs was highly associated with H3K9ac alteration through integrative analysis of chromatin immunoprecipitation with sequencing (ChIP-seq) and RNA-seq data in Populus trichocarpa subjected to soil-water depletion. We analyzed promoters of PtrNACs, and identified transcription factor (TF) PtrAREB1s that may be involved in regulating transcription of PtrNACs. Moreover, we identified a drought inducible histone acetyltransferase (HAT) gene, PtrGCN5-1, encoding a protein which is the catalytic subunit of several multiprotein HAT complexes, and a drought inducible adaptor protein gene PtrADA2b which is integral parts of GCN5-containing complexes. We also identified a drought inducible alternative PtrADA2b splice variant, PtrADA2b-α, which may be involved in an alternative splicing regulatory mechanism linking histone acetylation and TFs in plant response to drought stress. In this proposed work, we will investigate crosstalk between PtrGCN5-1, PtrADA2b, PtrADA2b-α and PtrAREB1s in regulation of H3K9ac on PtrNACs to activate their transcription, and analyze the roles of PtrGCN5-1, PtrADA2b, PtrADA2b-α, PtrAREB1s and PtrNACs in P. trichocarpa response to drought stress. We will also identify the direct targets of PtrNACs and find out their metabolic pathway in response to drought stress. Learning crosstalk between TFs and H3K9ac in response to drought stress will allow us to reveal the mechanisms of the combined action of TFs and histone modifications in regulation of drought responsive genes and also have broad utility in improving drought tolerance of tree species and forest productivity.