Characterization of the Coronatine-Like Phytotoxins Produced by the Common Scab Pathogen Streptomyces scabies
Characterization of the Coronatine-Like Phytotoxins Produced by the Common Scab Pathogen Streptomyces scabies
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DOI：
10.1094/mpmi-09-14-0255-r
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发表时间：
2015-04-01
影响因子：
3.5
通讯作者：
Bignell, Dawn R. D.
中科院分区：
文献类型：
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作者：
Fyans, Joanna K.;Altowairish, Mead S.;Bignell, Dawn R. D.
疥疮链霉菌是马铃薯块茎和其他块根作物常见的疥疮病的重要病原体。这种病原体产生的主要毒力因子是一种称为thaxtomin a的植物毒性次级代谢物，它对疾病的发展至关重要。此外，疥疮链球菌的基因组中还含有一个与毒力相关的生物合成基因簇，称为冠状酸（CFA）样基因簇，该基因簇先前被预测会产生类似丁香假单胞菌冠状碱（COR）植物毒素的代谢物。COR由CFA连接到称为冠状酸的乙基环丙基氨基酸，冠状酸衍生自l -异亮氨酸。结合遗传和化学分析，我们发现疥疮链球菌cfa样基因簇负责产生cfa -l -异亮氨酸作为主要产物，以及其他次要的cfa样代谢物。研究表明，代谢产物的产生需要cfl基因，该基因位于CFA样基因簇中，并编码一种酶，参与将CFA与其氨基酸伴侣连接起来。从疥疮链球菌培养物中纯化的cfa - l -异亮氨酸显示出与COR相似的生物活性，尽管发现其毒性低于COR。这是第一个证明疥疮链球菌产生冠状酰基植物毒素的报告，疥疮是北美最普遍的疥疮病原体。
Streptomyces scabies is an important causative agent of common scab disease of potato tubers and other root crops. The primary virulence factor produced by this pathogen is a phytotoxic secondary metabolite called thaxtomin A, which is essential for disease development. In addition, the genome of S. scabies harbors a virulence-associated biosynthetic gene cluster called the coronafacic acid (CFA)-like gene cluster, which was previously predicted to produce metabolites that resemble the Pseudomonas syringae coronatine (COR) phytotoxin. COR consists of CFA linked to an ethylcyclopropyl amino acid called coronamic acid, which is derived from L-allo-isoleucine. Using a combination of genetic and chemical analyses, we show that the S. scabies CFA-like gene cluster is responsible for producing CFA-L-isoleucine as the major product as well as other minor COR-like metabolites. Production of the metabolites was shown to require the cfl gene, which is located within the CFA-like gene cluster and encodes an enzyme involved in ligating CFA to its amino acid partner. CFA-L-isoleucine purified from S. scabies cultures was shown to exhibit bioactivity similar to that of COR, though it was found to be less toxic than COR. This is the first report demonstrating the production of coronafacoyl phytotoxins by S. scabies, which is the most prevalent scab-causing pathogen in North America.