木本植物的次生生长是木材形成的基础，次生生长的调控是高度复杂的动态过程，对其机制的解析仍需大量深入的工作。生长调节因子（Growth-Regulating Factor, GRF）调控植物茎、叶以及分生组织等的发育，在生长调节中发挥重要作用，但其在木本植物生长发育尤其是次生生长中的作用还不清楚。基于杨树次生维管再生系统，我们发现，PtGRF10在形成层形成期非常活跃，表明它可能在次生生长过程中发挥重要作用。本项目拟通过创制PtGRF10过表达与下调表达等转基因材料，明确其在次生生长过程中的生物学效应；通过RNA-seq和ChIP-seq分析等，揭示PtGRF10调控的下游靶基因；通过激素处理，探索PtGRF10通路与激素的关系，最终系统解析PtGRF10所介导的信号通路，阐明PtGRF10调控次生生长的分子机制。这些研究将为林木速生优质遗传改良提供理论基础与候选基因。

Secondary growth is one of the basic molecular processes for wood formation. The regulations on the secondary growth were dynamic, complex processes, which were still elusive in woody plants. Growth-Regulating Factors (GRFs) have been shown to be involved in various developmental events, such as leaf development, stem elongation, root growth, and meristem zone size control, demonstrating important roles in growth regulation. Based on expression analyses of GRF genes during the regenerating secondary vascular system in Populus, PtGRF10 is significantly upregulated in the cambium formation stage, indicating the function in secondary growth. In this study, we aim to characterize the molecular mechanism of PtGRF10 in regulating secondary growth. The proposed studies include: 1) generate PtGRF10mt (with mutations in the miR396 target site) and PtGRF10-SRDX transgenic plants to elucidate the biological functions of PtGRF10; 2) identify targeted genes via RNA-seq and ChIP-seq analyses; 3) elucidate the effects of various hormones on PtGRF10 pathway. The achievements of this research will extend our understanding on secondary growth regulation and provide molecular basis and candidate gene for genetic improvement breeding on fast growing and high quality.