木质素是纸浆造纸和生物质能源有效利用的主要障碍。目前关于转录因子介导的调控木质素含量、结构的转录水平调控并不清楚。本研究将以木本模式植物毛果杨（Populus trichocarpa）为材料，建立调控木材形成中木质素含量及结构完整的多级分层转录遗传调控网络。我们将通过不同程度抑制木质素单体合成途径中所有酶基因的表达来降低木质素含量或改变木质素结构。在利用本团队已建立的网络构建演算法则基础上，通过系统分析转基因植株的转录组差异基因，建立一个多级分层转录遗传调控网络，描述与木材形成相关的转录因子及其调控特异木质素单体合成的功能基因。通过高效的木质部原生质体转录因子-DNA互作系统验证调控网络并定量描述特异转录因子与其调节的相关性状，如木质素量及结构。本研究将建立一个最全面的调控木质素合成机制方面的转录调控系统，并将为纸浆造纸及生物质能源生产用材树种的遗传改良提供理论指导。

Lignin is a barrier to efficient biomass utilization for the production of pulp and paper or biofuels. Our knowledge of the transcription factor (TF) mediated transcriptional regulation of monolignol biosynthesis for lignin content and structure is almost completely lacking.In this proposed project, we will use Populustrichocarpaas the model system to establish a complete hierarchical transcriptional genetic regulatory network that regulates monolignol biosynthesis for lignin quantity and structure (monolignol S/G ratio) during wood formation. We will perturb all monolignol pathway genes to generate transgenic P.trichocarpa lines with a wide range of lignin reductions and lignin S/G alternations.This large transgenic collection will be systematically characterized for transcriptome responses using our well-developed network construction algorithms to establish a hierarchical transcriptional genetic regulatory network. This networkwill describe all possible wood formation related TFs and their transregulatory relationships (upper hierarchical layers) that regulate specific monolignol biosynthesis genes (the regulatory target genes at bottom).We will then use our robust differentiating xylem protoplast-based TF-DNA interaction system to experimentally validate the regulatory network to quantitatively describe the specific transcription regulation for specific traits -- the lignin quantity and S/G ratio. The proposed project will provide the most comprehensive analysis of the transcriptional regulation of lignin biosynthesis ever undertaken in the world.The knowledge obtained will lead to precise strategies for manipulating the biosynthesis of lignin for improved wood traits for pulp and paper and biofuel production.