Dimorphic growth and resting structure development in plant pathogenic verticillium species

大丽轮枝菌（Verticillium dahliae）、白孢轮枝菌（V. albo-atrum）和长孢轮枝菌（V. longisporum）是土传真菌，它们在加拿大和世界各地商业种植的多种一年生作物和多年生作物（包括番茄、马铃薯、油菜和其他芸苔作物）中引起维管枯萎病。 这些病原体的土壤生境、感染期间难以接近以及它们在土壤中存活多年的能力，对疾病控制构成了巨大挑战。 很少有抗黄萎病的品种，化学熏蒸剂，减少土壤中的大丽轮枝菌的水平，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。 一种具有很大潜力的疾病控制方法是特异性地靶向并干扰对于轮枝菌在植物中的生长和/或其在土壤中的存活至关重要的分子过程。 拟议的研究计划将集中在分子和遗传学研究：1）长寿的休眠结构，微菌核或黑化菌丝体的发展，这是在垂死的植物组织中产生的，并提供疾病接种物的主要来源，和2）二型生长（产生酵母样孢子和菌丝体），这发生在液体培养中，并在植物维管系统感染期间。 先前的研究表明，大丽轮枝菌携带一个编码疏水蛋白的基因，该蛋白是产生微菌核所必需的。 同样的基因在V. albo-atrum中被鉴定，它不产生微菌核;因此该基因在V. albo-atrum中的作用是未知的。 将使用报告基因、突变和生物化学分析来比较这些基因及其各自蛋白质在V. albo-atrum和V. dahliae中的表达。 此外，DNA微阵列分析将用于识别在静息结构发育和/或二态生长期间高度表达的其他基因。 这些基因将是进一步表征的候选基因。

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.