Virulence mechanisms of plant pathogenic Streptomyces species

马铃薯赤霉病是一种重要的植物病害，在加拿大许多马铃薯产区都有发生。这种病的特点是在马铃薯块茎表面形成浅的或凸起的软木塞状损伤。这些病害影响了马铃薯作物的适销性，给马铃薯种植者带来了巨大的经济损失。2002年，加拿大马铃薯赤霉病造成的总经济损失估计在1,500-1,700万美元之间，突显了这种疾病对加拿大马铃薯产业和整个经济的重要性。 一种常见的结痂病原体是一种寄居在土壤中的丝状细菌，称为链霉菌结痂。由这种微生物引起的疾病症状主要是由于产生一种名为红曲霉素A的植物毒素，这种毒素的功能是纤维素合成抑制物。此外，其他已知或推定的毒力决定因素已被确定，这些决定因素被认为有助于由链霉菌引起的疾病症状的严重程度。 这项研究的短期目标是鉴定一种新发现的次生代谢物生物合成簇的产物，该簇对链霉菌的毒力具有重要作用。这种代谢物将从链球菌培养物中提纯，以便确定其结构，并评估其对疾病症状发展的贡献。此外，这种代谢物的生物合成将通过构建疮疮链霉菌基因缺失进行检测。这项研究的结果将为深入了解溃疡链霉菌致病的分子机制提供重要的启示，这是本研究的长期目标。预计获得的信息将有助于更好地了解农业环境中赤霉病的发展，并可能提出更有效的方法来控制它和引起它的病原体。此外，这项研究将通过培训学生的技术使他们能够在学术机构或政府或行业实验室追求成功的研究生涯，从而使加拿大受益。

Potato common scab is an important plant disease that occurs in many potato growing regions in Canada. The disease is characterized by superficial or raised corky-like lesions that form on the surface of the potato tuber. These lesions affect the marketability of the potato crop leading to significant economic losses for potato growers. In 2002, the total economic loss to potato scab in Canada was estimated to be between $15-17 million dollars, highlighting the importance of this disease to the Canadian potato industry and the economy as a whole. A causative agent of common scab is a soil-dwelling, filamentous bacterium called Streptomyces scabies. The disease symptoms induced by this organism are mainly due to production of a phytotoxin called thaxtomin A, which functions as a cellulose synthesis inhibitor. In addition, other known or putative virulence determinants have been identified that are thought to contribute to the severity of disease symptoms caused by S. scabies. The short-term goal of this research is to characterize the product of a newly-discovered secondary metabolite biosynthetic cluster that is important for virulence in S. scabies. The metabolite will be purified from S. scabies cultures so that its structure can be determined and its contribution to disease symptom development can be assessed. In addition, the biosynthesis of this metabolite will be examined through construction of S. scabies gene deletions. The results of this study will provide important insight into the molecular mechanisms of pathogenicity in S. scabies, which is the long-term goal of this research. It is anticipated that the information gained will lead to a better understanding of scab disease development in agricultural settings and may suggest more effective ways of controlling it and the pathogens that cause it. In addition, this research will benefit Canada by training students in techniques that will allow them to pursue successful research careers at academic institutions or in government or industry labs.