Genetics of Coronatine Biosynthesis in Pseudomonas Syringae pv. Tomato

诱导黄化的植物毒素coronatine具有一种特殊的结构，由一个聚酮组成，它与一个乙基环丙基环相连。与丁香假单胞菌产生的其他植物毒素不同，冠状碱是由多种具有不同宿主特异性的病原体产生的。尽管冠状碱在产生病原菌的毒力中具有重要作用，但冠状碱生物合成的遗传学尚未得到系统的研究。利用转座子诱变技术，获得了丁香花冠状蛋白缺陷突变体。番茄。这些突变体的物理分析表明，一个101 kb的质粒（命名为pPT23A）参与了冠状碱的合成。随后将pPT23A转移到丁香假单胞菌pv中。丁香属PS61，不产生冠状碱。在获得pPT23A后，PS61获得了制造coronatine的能力。因此，收集了质粒pPT23A参与冠状碱产生的确凿证据。本提案中概述的实验将通过分子克隆，诱变和互补实验精确定义pPT23A参与冠状碱生物合成的区域。这些实验的结果将促进植物毒素遗传学领域的知识。

The chlorosis-inducing phytotoxin coronatine has an unusual structure and consists of a polyketide component joined to an ethylcyclopropyl ring. In contrast to other phytotoxins produced by Pseudomonas syringae, coronatine is produced by multiple pathovars with distinct host specificity. Despite the importance of coronatine in the virulence of producing pathovars the genetics of coronatine biosynthesis has not been systematically studied. Transposon mutagenesis was used to generate coronatine- defective mutants of P. syringae pv. tomato. The physical analysis of these mutants suggested the involvement of a 101 kb plasmid (designated pPT23A) in coronatine synthesis. pPT23A was subsequently transferred into P. syringae pv. syringae PS61, a nonproducer of coronatine. Upon acquisition of pPT23A, PS61 gained the ability to make coronatine. Therefore, conclusive evidence has been collected for the involvement of plasmid pPT23A in production of coronatine. The experiments outlined in this proposal will precisely define the regions of pPT23A involved in coronatine biosynthesis by moleuclar cloning, mutagenesis, and complementation experiments. The results of these proposed experiments will advance knowledge in the area of phytotoxin genetics.