Urease metabolism in the wheat pathogen Zymoseptoria tritici

病原真菌能够感知和调节其环境的PH值。这确保了当地的pH对它们的生长和分泌的毒力因子的活性是最佳的。病原体对pH值的操纵也会对宿主提高全面免疫反应的能力产生不利影响。真菌在含氮化合物的分解代谢过程中产生氨，它的产生会导致当地环境的碱化。氨被一系列不同的植物和动物真菌病原体用来调节pH值，如番茄病原体Colletotrichum Gloeosporioids和人类病原体白色念珠菌。尿素酶是一种重要的pH调节器，它将尿素转化为氨和二氧化碳，是人类真菌病原体新生隐球菌和拟球虫致病所必需的。我们感兴趣的是确定尿素酶在多大程度上是一种一般的真菌毒力因子，因为它作为抗真菌靶标的潜力。尿素酶是目前已知的唯一一种含镍真核生物酶，其成熟过程涉及多种辅助蛋白。这种复杂性为尿素酶失活提供了许多靶点。我们已经确定了新生隐孢子菌中尿素酶成熟的特征，在这个项目中，我们将在小麦病原菌ZymosepVictoria tritici中进行类似的研究。我们的初步研究证明，小麦纹枯病菌是一种尿素酶阳性微生物。我们将测试假设，即尿素酶活性调节这种真菌的外部pH，这一过程是需要这种重要的病原菌的毒力。学生将使用一系列分子技术来研究尿素代谢和缺乏尿素酶及其成熟所需的辅助蛋白的小麦纹枯病菌突变体的毒力。还将对Z.tritici尿素和镍转运体进行结构研究。该项目属于BBSRC农业和食品安全的战略优先事项。在世界范围内，小麦是人类食物中植物蛋白的主要来源，因此保护这一食物来源的供应至关重要。令人担忧的是感染小麦并降低农业产量的真菌病原体。小麦纹枯病菌引起世界各地发生的小麦斑点病，在发展中国家可能是一个严重的问题。在严重的流行病中，小麦产量可能减少高达50%。小麦黑斑病是欧洲最严重的小麦病害，在英国每年造成5000万GB的经济损失。虽然有多种杀菌剂被用来控制小麦纹枯病菌，但许多种群已经对杀菌剂产生了抗药性，因此需要新的杀菌剂靶标。了解尿素酶在小麦纹枯病菌感染循环中的作用将有助于开发新的策略来控制这种重要的病原体。

Pathogenic fungi are able to sense and modulate the pH of their environment. This ensures that the local pH is optimal for their growth and the activity of secreted virulence factors. Manipulation of pH by pathogens can also have a detrimental impact on the ability of the host to raise a full immune response. Fungi produce ammonia during the catabolism of nitrogenous compounds and its generation results in alkalinisation of the local environment. Ammonia is used to modulate pH by a diverse range of plant and animal fungal pathogens such as the tomato pathogen Colletotrichum gloeosporioides and the human pathogen Candida albicans. The urease enzyme is an important pH regulator as it converts urea into ammonia and carbon dioxide and is required for the virulence of the human fungal pathogens Cryptococcus neoformans and Coccidioides posadasii. We are interested in determining to what extent urease is a general fungal virulence factor due to its potential as an antifungal target. Urease is the only known nickel containing eukaryotic enzyme and urease maturation involves multiple accessory proteins. This complexity provides many targets for urease inactivation. We have characterised aspects of urease maturation in C. neoformans and during this project will undertake similar studies in the wheat pathogen Zymoseptoria tritici. Our preliminary studies have established that Z. tritici is a urease positive organism. We will test the hypothesis that the urease activity of Z. tritici modulates the external pH of this fungus and that this process is required for the virulence of this important pathogen. The student will use a range of molecular techniques to study urea metabolism and the virulence of Z. tritici mutants lacking urease and the accessory proteins required for its maturation. Structural studies of the Z. tritici urea and nickel transporters will also be undertaken. This project falls within the BBSRC strategic priority of agriculture and food safety. Worldwide, wheat is the major source of vegetable protein in human food so it is essential that the supply of this food source is protected. Of concern are fungal pathogens that infect wheat and reduce agricultural yields. Z. tritici causes septoria tritici blotch disease that occurs throughout the world and can be a significant problem in developing countries. In severe epidemics wheat yields can be reduced by up to 50%. Septoria tritici blotch disease is the most serious wheat disease in Europe and in the UK results in an annual financial loss of £50 million. Although several fungicides are used to control Z. tritici many populations have evolved fungicide resistance so that new fungicidal targets are needed. Understanding the role of the urease enzyme during the infection cycle of Z. tritici will help in the development of new strategies to control this important pathogen