平头炭疽菌寄主范围极广，且常与不同炭疽种复合侵染，造成严重经济损失，生产上主要采用化学药剂进行防治。然而，平头炭疽菌对部分DMIs药剂表现为天然抗性，难以防控。项目申请人前期在平头炭疽菌中克隆到一个和甾醇合成相关的转录因子CtSR，发现其缺失，会导致CtCYP51s表达量显著降低，DMIs敏感性显著上升，推测CtSR通过调控CtCYP51s表达从而导致了DMIs天然抗性的产生。本项目拟通过酵母单杂交、EMSA等方法明确CtSR靶向的CYP51s上游顺式作用元件，比较DMIs敏感性不同的炭疽种中CYP51s表达量差异，明确CtCYP51s是否存在过表达。选择对DMIs敏感的近缘种，果生炭疽菌，转化平头炭疽菌的CtCYP51s，并通过定点突变及蛋白结合光谱实验，明确造成天然抗性的具体点突变。该项目将为设计研发以CYP51为特异性靶标的新型杀菌剂提供理论依据和研究基础。

Colletotrichum truncatum has a wide range of hosts, and often cause anthracnose in the same plant host with other species, costing serious economic losses. The control of the disease mainly depends on the use of fungicides. The previous studies showed that C. truncatum was inherently resistant to some DMIs. In our previous study, a transcriptional factor CtSR associated with sterol synthesis was cloned from C. truncatum. After the deletion of CtSR, the expression levels of CtCYP51s decreased significantly and the sensitivity to DMIs increased significantly compared to their wild parent. It was speculated that CtSR regulated the expression of CtCYP51s to cause the inherent resistance to DMIs in C. truncatum. The project aims to determine the cis-acting elements interacted with CtSR in the upstream of CtCYP51s by using yeast one-hybrid and EMSA methods. The expression of CYP51A and CYP51B in different Colletotrichum spp. to different DMIs will be analyzed to determine whether CtCYP51s were overexpressed in C. truncatum. The relationship between CtCYP51s and DMIs resistance will be defined by transforming CYP51s from the inherently resistant C. truncatum isolates to its close-related DMIs sensitive C. fructicola isolates. To further investigate the affinity differences between mutant proteins and DMIs, site-directed mutagenesis will be used together with protein binding spectroscopy. The project will eventually provide a theoretical basis for the development of new fungicides targeted on CYP51s.