揭示木材形成分子机制是木材品质分子改良的前提。木质部细胞分化是典型的程序性细胞死亡（PCD），最终形成木材。PCD过程中DNA损伤可引起RETINOBLASTOMA RELATED（RBR）介导的细胞分化。XYLEM NAC DOMAIN1（XND1）是木质部发育重要负调控因子，在拟南芥中与RBR共同行使功能。申请人前期研究表明杨树核酸酶基因PagCAN1过表达引起DNA损伤促进木质部发育，提示DNA损伤启动PCD激活木质部分化相关基因表达。本项目拟利用酵母双杂、双分子荧光互补、免疫共沉淀分析DNA损伤响应因子PagRBR与木质部发育关键因子PagXND1的互作，明确PagXND1调控活性与DNA损伤（PCD）关系。进一步由染色质免疫共沉淀、双荧光素酶报告明确PagXND1对下游靶基因调控。通过揭示DNA损伤下PagXND1如何参与杨树木质部发育的调控，为木本植物木材材性研究提供理论基础。

Elucidation of the molecular mechanisms of wood formation provides better guidance on improvement of wood quality. Xylem differentiation (wood formation) is a typical process of developmental programmed cell death (PCD). RETINOBLASTOMA RELATED（RBR） is involved in cell differentiation in response to DNA damage during PCD. XYLEM NAC DOMAIN1 (XND1), a master transcription factor, negatively regulates xylem development and is recently found interacting with RBR in Arabidopsis. We have found that overexpression of the nuclease PagCAN1 can enhance DNA fragmentation followed by xylem differentiation in poplar, indicating that DNA fragmentation initiates PCD and activates genes involved in xylem development. Thus we propose to investigate the interactions between PagRBR and PagXND1 via yeast two-hybrid, bimolecular fluorescence complement and co-immunoprecipitation to illustrate the activity of XND1 in response to DNA damage, and further to verify the target genes of PagXND1 via chromatin immunoprecipitation and transactivation assay. This work will contribute to unraveling the regulation mechanism of PagXND1 involved in xylem differentiation response to DNA damage, providing a knowledge on research and improvement of wood quality.