抗菌脂肽orfamide A是Pseudomonas protegens防治植物病害的重要生防因子。项目组前期发现，在该生防菌中，环二肽cEL与信号受体LuxP/LuxQ组成一种新型群体感应系统。该系统能调控orfamide A的合成，还能影响orfamide A合成中的调控元件sRNA(rsmY/Z)的转录。这表明，该菌株中存在一种环二肽cEL介导的sRNA调控orfamide A合成的信号途径，但机制尚不清楚。基于此，本项目将阐明该信号系统对下游元件（LuxU/LuxO）磷酸化的调控作用；鉴定受LuxO直接调控的sRNA；研究该sRNA与阻遏蛋白（RsmA/E）组成的Rsm系统的作用靶标，揭示Rsm系统在调控orfamide A合成中的生物学功能。预期研究结果将阐明新型信号分子cEL调控orfamide A合成的分子机制；为提高orfamide A的产量提供基因靶标。

Antimicrobial lipopeptide orfamide A play the key role in using Pseudomonas protegens control plant disease. Our previous studies had showed that cyclodipeptide cEL (cyclo-L-Glu-L-Leu) and LuxP/LuxQ can form a novel quorum sensing (QS) system in P. protegens. This system can regulate the synthesis of orfamide A, and also influence the transcription of sRNA(rsmY/Z). These sRNA are the key regulatory elements in synthesis of orfamide A. These means this strain could use the signal cEL to mediate sRNA to regulate the synthesis of orfamide A. But the regulatory mechanism is unknown. On the basis of previous work, in this project, we will clarify the regulatory role of this QS system on phosphorylation of downstream components (LuxU/LuxO). We will also identify which kind of sRNA is directly regulated by phosphorylated LuxO. The targets for Rsm system which is formed by sRNA and repressor protein ( RsmA/E) will be studied. And the function of this Rsm in regulating the synthesis of orfamide A will be clarified. This study will elucidate the molecular mechanism of a novel quorum sensing signal cEL regulating the synthesis of orfamide A, will provide target gene for enhancing the yield of orfamide A.