Characterization of Avirulence Genes from Pseudomonas syringae pv. tomato

本实验室克隆并鉴定了来自丁香假单胞菌群细菌病原体的几个无毒基因，这些基因负责大豆植物的防御监视。其中一个基因是丁香假单胞菌的avrD。番茄，使细菌宿主精心制作细胞外激发剂化合物。分离的激发子仅对含有互补抗病基因Rpg4的大豆品种产生超敏反应。AvrD还有其他几个有趣的特征，例如它与其他四个相关基因一起出现在本地细菌质粒上，当细菌在大豆叶片中生长时，与培养基相比，其诱导率为100倍。因此，携带avrD的细菌与植物宿主的相互作用涉及到在两种生物中启动精确发育程序的相互信号机制。本提案要求进一步研究avrD及其在启动植物抗病中的作用：1)确定avrD启动子的特征；2)阐明植物诱导avrD的性质；3)研究发生avrD的原生质粒；4)将avrD与其他丁香假单胞菌病原菌的同源基因进行比较。该研究将有助于我们对植物-微生物信号传导机制和植物抗病性的理解。

This laboratory has cloned and characterized several avirulence genes from bacterial pathogens in the Pseudomonas syringae group that are responsible for defensive surveillance by soybean plants. One of these genes, avrD from P. syringae pv. tomato, causes bacterial hosts to elaborate an extracellular elicitor compound. The isolated elicitor causes the hypersensitive response (HR) only on soybean cultivars containing thecomplementary disease resistance gene, Rpg4. AvrD also has several other interesting features such as its occurrence, along with four other linked genes, on an indigenous bacterial plasmid and its 100-fold induction when bacteria are grown in soybean leaves as compared to culture media. The interaction of bacteria carrying avrD with plant hosts therefore involves reciprocal signalling mechanisms that initiate precise developmentalprograms in both organisms. This proposal requests support to further study avrD and its role in initiating plant disease resistance by 1) characterizing the avrD elicitor; 2) elucidating the nature of plant induction of avrD; 3) studying the indigenous plasmid on which avrD occurs and 4) comparing avrD withhomologous genes that occur in other P. syringae pathovars. The proposed research should contribute significantly to our understanding of plant-microbe signalling mechanisms and disease resistance in plants.