半胱氨酸蛋白酶(cysteine protease，CP) 通过激活自身酶活性，以及其他蛋白酶、核酸酶的活性来启动并执行植物细胞自发进行的程序化死亡（PCD）过程。树木木材形成过程是木质部细胞自发进行程序化死亡（PCD）的过程。本项目以杨树为材料，在分析毛白杨木质部、韧皮部、根、叶、芽等部位转录组芯片数据的基础上，分析出可能在杨树木质部细胞程序化死亡（PCD）过程起重要过程的4个半胱氨酸蛋白酶基因。通过原位杂交、GFP荧光定位等技术进一步分析这些基因在杨树木质部发育各阶段中的表达、运输和分布规律；同时利用原核表达技术，研究该酶的生化特性与功能；最后通过转基因技术在杨树体内过量或缺失表达这些半胱氨酸蛋白酶基因，进一步分析这些基因的过量或缺失表达对杨树木质部发育的影响；从而全面阐述杨树半胱氨酸蛋白酶基因参与杨树木质部发育与木材形成过程的表达与调控机制，为林木木材形成与品质控制提供理论基础。

Cysteine proteases are intimately involved at control points by activates other member proteases, cause the destruction of various cellular targets, leading to cell death. Wood forming is the progress of xylem cell differentiation, programmed cell death and construction of secondary xylem.To understand the mechanism for cysteine protease in xylem differentiation and PCD progress in Populus, four the CEP1-like types of cysteine protease participated in xylem differentiation and PCD progress in Populus would be analyzed. The expression of four CEP1-like cysteine protease in the progress of xylem development would be analysis by in situ hybridization. The enzyme activity would be analysis after expression and purity in E.Coli. At last, the role of cysteine protease participated in xylem differentiation and PCD progress would also be analysis by loss or over-expression technology. It would be used to more undestand the molecular mechanisms of wood forming.