Dickeya zeae菌株EC1是自广东水稻基腐病组织分离的一株致病菌，可产生抑制水稻种子萌发的毒素。研究证明，该毒素为聚酮多胺类抗生素，其中zeamine（C49H105O4N6）占EC1产毒量的60%，zeamineⅡ（C40H88ON5）占40%。在前期研究中，我们通过Tn5转座子插入突变、TAIL-PCR扩增及测序，克隆分析了一个聚酮合成酶编码基因zmsA，基因敲除证明ZmsA参与zeamine的生物合成，另外还获得了近20个毒素产生明显减少的Tn5插入突变体。本课题拟用hiTAIL-PCR方法结合基因组测序结果，对突变体进行分子鉴定，用生物信息学方法对克隆的基因进行功能预测，用基因敲除、功能互补及中间产物分析手段进行功能验证，以揭示这些基因在zeamine生物合成及致病过程中的作用。研究结果可为合成生物学提供线索，通过对结构基因等的改造提高zeamine产量或产生新的衍生物。

Dickeya zeae is the causal agent of the rice foot rot disease. Compared with other closely related species, strain EC1 can produce toxins that inhibit the germination of rice seeds. Through collaborative research, active compounds were purified from D. zeae EC1 and were structurally characterized, and the results have unveiled two polyamino compounds, i.e., zeamine (C49H105O4N6) and zeamine II (C40H88ON5), accounting for 60% and 40% of the total toxins produced, respectively. Recently, zmsA that encodes a novel polyketide synthase has been cloned through Tn5 transposon mutagenesis and TAIL-PCR analysis. Deletion mutagenesis confirmed that ZmsA is essential for zeamine biosynthesis and bacterial virulence. In addition, we have also obtained about 20 Tn5 inserted mutants which were defective in toxin production. In this study, we aim to identify and characterize the mutated genes and understand their roles in biosynthesis of zeamines and in bacterial pathogenesis through gene knockout, complementation and metabolite analysis. The results would facilitate understanding the roles of various enzymes in zeamine synthesis pathway and in pathogenesis, and may also provide useful clues for synthetic biology in engineering of high potency and safe antibiotics with low side-effects.