干旱是森林生态系统中较为频繁发生的环境灾害。树木次生木质部形成木材，是运输水分的关键组织。干旱胁迫下树木会改变生长发育过程，形成减缓胁迫损害的特性细胞。我们前期研究发现PtrNAC006基因在毛果杨木质部的表达受干旱诱导，过表达该基因后植株耐旱性显著增强，且茎干具有较多孔径较小的导管细胞。大量研究表明这种细胞特性利于增强植株耐旱性。但PtrNAC006调控哪些基因来改变导管形态适应干旱尚不清楚。本项目拟利用激光显微切割精确收集PtrNAC006过表达植株分化木质部导管和纤维细胞，RNA-seq对比分析鉴定PtrNAC006调控的导管特异性基因。结合以PtrNAC006单克隆抗体为基础的ChIP-seq，在全基因组鉴定PtrNAC006调控的导管形成的直接靶基因调控网络，揭示PtrNAC006调控哪些基因导致导管优化耐旱的机制，为培育抗旱树种增加森林生产量提供理论借鉴。

Drought is a recurrent stress to forests ecosystem. Secondary xylem develops to wood, and is the water-conducting tissue of tree stems. Trees modify wood development to create anatomical features that can mitigate drought stress. In previous research, we found that the expression level of PtrNAC006 transcription factor gene in xylem tissue of Populus trichocarpa was highly induced by drought stress, and overexpressing PtrNAC006 gene in P. trichocarpa resulted in drought-tolerance phenotypes with more and smaller vessel cells. A large number of studies show that these anatomical features can improve the drought tolerance in plants. Unfortunately, genes regulated by PtrNAC006 to modify vessel features adapt to drought stress are poorly understood. In this proposed work, we will isolate drought adaptive vessel cells and fiber cells in differentiating xylem of PtrNAC006 overexpression plants by laser capture microdissection (LCM) followed by RNA-seq analysis. Comparing the results of two cell types RNA-seq data, we will identify vessel-specific formation genes regulated by PtrNAC006. Integrative analysis of these vessel-specific genes with monoclonal anti-PtrNAC006 antibody-based ChIP-seq, PtrNAC006’s direct target genes, at the whole genome basis, that are related to the formation of drought-tolerant vessel types will be identified. This will allow the construction of a transcriptional regulatory network (TRN) for vessel formation mediated by PtrNAC006 in response to drought stress. From this TRN we then can identify which genes are regulated by PtrNAC006 and their effects on the features of vessels underlying the drought resistance mechanisms. This proposed work will provide new knowledge of how to effectively produce drought tolerance tree species to improve forest productivity.