密度感应抑制技术为环境友好型植物病害防治策略，AHL内酯酶能够降解信号分子AHL，是实现该技术的重要途径之一。申请人所在实验室在海洋细菌耐油具柄菌中发现一种新型AHL内酯酶MomL，其降解中长链AHL效率高，C6-HSL降解效率kcat/Km达2.9×105s-1M-1，并随AHL链长的增加，降解效率逐步提高。momL位置特殊，位于铁硫簇suf基因簇内部。本课题将研究momL与suf的调控相关性，对suf及调控基因iscR进行转录调控分析，提高momL原菌表达水平，从而提高菌株防病害效力。研究MomL高活力及宽底物范围机制，确立关键氨基酸的作用。结合定向进化和成熟的高通量筛选技术，分析 MomL及高活力突变体蛋白在抑制七种植物病原菌致病性方面的效力，并应用于植物软腐病防治。海洋来源的AHL内酯酶处于高度未开发状态，本项目有助于该类酶的进一步开发研究，也为海洋资源应用于植物保护提供研究基础。

Quorum quenching technology is a environmental-friendly strategy for plant disease control. AHL lactonase, degrading signal molecular N-Acyl homoserine lactone (AHL), is one of the important factors for quorum quenching. Recently, a new kind of AHL lactonase MomL, which was exploited from marine microorganism Muricauda olearia Th120, was studied in our group. The catalytic efficiency (kcat/Km) of MomL for C6-HSL is up to 2.9×105s-1M-1. The AHL degrading efficiency will increasingly improve with the carbon chain extension of different kind of AHL. momL gene locates in between suf, which is a iron-sulfur cluster. This interesting phenomena suggests that momL possesses special transcriptional regulation mechanism. In this study, we will focus our study on the transcriptional relationship of momL and Fe-S cluster suf, analyzing the regulatory mechanism of suf and upstream regulatory gene iscR, which can lead us to up-regulate the expression level of MomL and increase the disease resistance of strain M. olearia Th120. We will also study the mechanism of highly catalytic efficiency and broadly substrate specificity of MomL, what is more, identify the function of key amino acids of MomL. Combined with directed evolution strategy and high throughput screening method for quorum quenching factors, the inhibition ability of MomL and positive mutants towards pathogenic bacteria will be studied. MomL will also be applied to therapy of soft rot disease. AHL lactonase from marine are largely unexploited. This project opens a way for future studies of this kind of enzymes and supplies fundamental research for its application in biological control area.