大豆疫霉(Ps)为重要土传病原卵菌，仅侵染大豆。普遍认为异黄酮是Ps侵染寄主的专化性信号分子，我们发现氨基酸和糖对Ps也有信号作用，但却不能解释为什么Ps对同样含有这些物质的菜豆根分泌物完全不应答，也不侵染轮作禾本作物。虽然有信号分子间阻滞报道，但缺乏对多种信号分子联合作用综合研究，更不清楚Ps应答机制。本项目拟在明确根分泌物中信号分子种类及水平基础上，研究Ps对多种信号分子联合作用应答机制。1) 充分挖掘、鉴定寄主、非寄主根分泌物中信号分子，明确对Ps诱导/抑制作用；2) 测定信号分子混合后对Ps信号强度变化，明确联合作用方式、强度及与Ps特异性发育变化关联浓度；3) 从发育变化和转录翻译层面分析Ps应答机制。通过对Ps与寄主、非寄主根分泌物中信号分子间关系研究，阐明Ps应答不同信号分子组合的差异，揭示其对Ps建立寄主专化性的贡献，为设计高效卵菌药剂，实现Ps根际行为预测和调节提供依据。

Phytophthora sojae (Ps) is an important soil-borne oomycete pathogen, whose host only restricts to soybean. Isoflavones in root exudates have been reported as host-specific signaling molecules during Ps infection in its host. We found that amino acids and sugars in root exudates also have chemoattractivity to Ps zoospores. However, it is not clear why Ps zoospores do not response to the root exudate from common bean, in which isoflavones and amino acids as well as sugars exist, and why Ps do not infect rotating graminaceous crops. Although, the mask or reduction in chemoattraction between two signaling molecules was reported, no comprehensive research on associative chemoattraction among several signaling molecules has been reported. Furthermore, the mechanism of Ps response to mixed signaling molecules is not clear. In this project, the mechanism of Ps response to mixed signaling molecules will be studied on the basis of understanding of main signaling molecules in root exudates and their secretion levels. 1) Mining and identifying signaling molecules in host and non-host root exudates, measuring their chemoattraction or suppression on Ps; 2) Measuring the changes in intensity of mixed signaling molecules, defining mode and intensity of associative chemoattraction as well as ecological relevant concentrations of chemoattractants corresponding to the specific developmental changes of Ps; 3) Revealing the mechanism of Ps response to mixed signaling molecules through the developmental changes and molecular responses of Ps to mixed signaling molecules. The research of the relationship of Ps and signaling molecules in host and non-host root exudates will elucidate the mechanism of Ps response to mixed signaling molecules in root exudates, reveal the contribution of the difference in responses of Ps to different combination of signaling molecules for Ps to establish its host specificity, and provide a basis for designing highly effective fungicides and realizing the prediction and regulation of the rhizosphere behavior of Ps.