Genetics of Coronatine Biosynthesis in Pseudomonas Syringae pv. Tomato

诱导黄化的植物毒素冠状毒素具有一种特殊的结构，由聚酮组分连接到乙基环丙基环上组成。与其他由丁香假单胞菌产生的植物毒素不同，冠状病毒是由多个具有不同寄主特异性的致病变种产生的。尽管冠状病毒在产生致病变种的毒力中很重要，但冠状病毒生物合成的遗传学还没有得到系统的研究。利用转座子诱变技术，获得了紫丁香疫霉冠状突变体。番茄。对这些突变体的物理分析表明，一个101kb的质粒(命名为pPT23A)参与了冠状病毒的合成。随后将pPT23A转入紫丁香P.syringae PV。紫丁香属PS61，一种非冠状产生菌。获得pPT23A后，PS61获得了制造冠状病毒的能力。因此，已有确凿证据证明pPT23A参与了冠状病毒的合成。本提案中概述的实验将通过分子克隆、突变和互补实验精确地定义参与冠状病毒生物合成的pPT23A区域。这些拟议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.