Dimorphic growth and resting structure development in plant pathogenic verticillium species

黄萎病(Verticillium Dahliae)、黄萎病(V.albo-Atrum)和黄萎病(V.Longisporum)都是土传真菌，在加拿大和世界各地的各种一年生作物和多年生植物上都能引起维管萎萎病，包括番茄、马铃薯、油菜和其他十字花科作物。由于这些病原菌的土壤生境，它们在感染期间难以接触，以及它们在土壤中存活多年的能力，给病害控制带来了巨大的挑战。现有的黄萎病抗性品种很少，而化学熏蒸剂降低土壤中的黄萎病水平，对环境有害，并破坏有益的土壤微生物。鉴于病原体目前和潜在的经济影响，必须考虑新的疾病控制方法。有一种很有潜力控制疾病的方法是专门针对和干预对轮枝菌在植物中的生长和/或在土壤中的生存至关重要的分子过程。拟议的研究计划将侧重于以下方面的分子和遗传学研究：1)在垂死的植物组织中产生的长期休眠结构、微菌核或黑化的菌丝体的发展，并提供主要的接种源；以及2)在液体培养中发生的二态生长(产生类似酵母的孢子和菌丝体)，以及在感染期间在植物的维管系统中。以前的研究表明，大丽弧菌携带一种基因，编码一种疏水蛋白，这是产生微菌核所必需的。但在不产生微菌核的阿尔博-阿特鲁姆弧菌中已经发现了同样的基因；因此，该基因在黑曲霉中的作用尚不清楚。将使用报告基因、突变和生化分析对这些基因在黑曲霉和大丽弧菌中的表达及其各自的蛋白质进行比较。此外，DNA微阵列分析将用于识别在静止结构发育和/或二态生长过程中高表达的其他基因。这些基因将成为进一步鉴定的候选基因。

Verticillium dahliae, V. albo-atrum, and V. longisporum are soilborne fungi that cause vascular wilt disease in a variety of annual crops and perennials that are grown commercially in Canada and worldwide, including tomato, potato, oilseed rape, and other brassica crops.  The soil habitat of these pathogens, their inaccessibility during infection, and their ability to survive for many years in the soil, pose formidable challenges to disease control.  Few verticillium wilt-resistant cultivars are available, and chemical fumigants, which reduce levels of V. dahliae in the soil, are environmentally harmful, and destroy beneficial soil microorganisms.  Given the present and potential economic impact of the pathogen, new approaches to disease control must be considered.    One approach with much potential for disease control is to specifically target, and interfere with, the molecular processes which are critical for the growth of Verticillum in the plant, and/or its survival in the soil.  The proposed research program will focus on molecular and genetic studies of: 1) the development of the long-lived resting structures, microsclerotia or melanized mycelia, which are produced in dying plant tissues, and provide the primary source of disease inoculum, and 2) dimorphic growth (production of both yeast-like spores and mycelia), which occurs in liquid culture, and in the plant vascular system during infection.  Previous studies have shown that V. dahliae carries a gene that encodes a hydrophobin protein which is required for microsclerotia production.  The same gene has been identified in V. albo-atrum, which does not produce microsclerotia; the role of this gene in V. albo-atrum is therefore unknown.  A comparison of expression in V. albo-atrum and V. dahliae of these genes, and their respective proteins, will be carried out using reporter genes, mutational, and biochemical analysis.  In addition, DNA microarray analyses will be used to identify additional genes that are highly expressed during resting structure development and/or dimorphic growth.  Such genes will be candidates for further characterization.