Novel approaches to investigating Ustilago maydis pathogenesis: meiosis, phytohormones and non-coding RNAs

在加拿大，锈菌和黑粉菌每年可造成数亿美元的损失，因为它们破坏了用于食品、林业和生物能源的作物。传统的研究并没有提供一种可持续的方法来控制它们。这项建议中的新方法提供了新的控制措施的可能性，这些措施可以给我们在控制这些真菌方面所需的优势。黑粉菌和锈菌都必须在植物中生长才能繁殖，当它们在植物中生长时，它们从植物中获取食物，同时保持植物的生命。这种真菌的“进食”被称为“生物营养”。要研究这些真菌，需要在实验室里培养它们的能力，而大多数锈菌只能生长在植物上，所以很难与之共事。相比之下，一些黑穗病真菌，特别是引起玉米黑穗病的那种，可以在实验室种植，相对容易研究。这项建议利用玉米黑粉菌来了解它是如何致病的，其想法是将这一知识转移到更难研究黑粉病和锈病的地方。这项提案的方法是独特的，因为它专注于调查：为什么黑穗病需要在植物中生长，黑穗病产生哪些化学物质对疾病的发展有很大影响，以及由于我们知道这些生物已经与植物生活了很长时间，它们的生活方式的核心是否有可能影响它们致病的能力。这些生物需要植物做的一件事就是做爱。这意味着当黑粉菌感染玉米时，它必须经历一个有性循环才能致病，这个循环的结果是产生黑色的煤烟真菌孢子来传播疾病。性周期和疾病周期同时发生的事实表明，真菌必须在控制其致病能力的同时控制其有性繁殖。因此，我们推断，如果我们能够理解它是如何控制性的，那么我们就会更好地理解它是如何控制疾病的。我们的早期研究很有希望，因为我们在其他生物体中发现了一种控制性别的基因，并发现它控制着玉米黑粉病的致病能力。我们正在研究这个基因在疾病发展过程中的功能。我们的研究还发现，玉米黑穗病真菌会产生自己版本的植物激素，它会释放这些激素来改变玉米植株的结构和生理。玉米黑穗病包括导致玉米细胞分裂并形成肿瘤的真菌，真菌在其中生长，然后将植物制造的营养重新定向到该肿瘤。基本上，这种真菌欺骗植物为它提供食物和生存的地方。我们正在努力了解黑穗病如何以及何时产生植物激素，以及真菌植物激素如何改变植物。最后，当我们研究这种生物的基因组序列时，我们发现了一些完全不同的东西。如果你认为基因组是细胞的图书馆，基因就是书，那么基因组的工作方式就是你复制书把它拿走。我们发现，很多时候，这本书的两个不同的副本被制作出来，并且这两个副本可以粘在一起(这两个副本代表正义和反义RNA)。事实证明，产生第二个基因拷贝是用来控制第一个拷贝的阅读，我们已经了解到，这种控制可能是生物体如何确定它是否会导致疾病。我们的调查将检验这一想法。拟议的研究结果将增加我们对真菌如何感染植物的理解。这将使我们能够设计出抗击黑穗病和锈菌的新方法，为我们减少疾病的斗争提供新的工具，并为我们提供更稳定的食物供应。

Rust and smut fungi can result in losses of $100s of millions in Canada each year because they devastate crops used for food, forestry and bioenergy. Traditional research has not provided a sustainable way to control them. The new approaches in this proposal provide the potential for novel control measures that could give us the edge we need in controlling these fungi. Both smut and rust fungi must grow in a plant to reproduce, and when they grow in the plant they take their food from the plant while keeping it alive. This type of `eating' by the fungus is called biotrophy. To study these fungi requires the ability to grow them in the lab and most of the rust fungi can only grow on the plant so they are difficult to work with. In contrast, some of the smut fungi, and particularly the one causing common smut of corn, can be grown in the lab and are relatively easy to study. This proposal uses the corn smut fungus to learn about how it causes disease with the idea of transferring this knowledge to the harder to study smuts and rusts. The approach of this proposal is unique as it focuses on investigating: why the smut needs to grow in the plant, what chemicals smuts produce that have a large impact on disease development and, since we know these organisms have lived with plants for a very long time, whether there is something about the very core of their life style that might influence their ability to cause disease. One thing that these organisms require plants for is sex. That means when the smut fungus infects corn it must go through a sexual cycle to cause disease and the outcome of this cycle is the production of black sooty fungal spores that spread the disease. The fact that the sexual cycle and the disease cycle occur at the same time suggests that the fungus must control its sexual reproduction at the same time that it controls its ability to cause disease. So we reasoned, that if we could understand how it controls sex then we would better understand how it controls disease. Our early investigations are promising because we identified a gene that controls sex in other organisms and found that it controls the ability to cause disease in corn smut. We are investigating the function of this gene during disease development. Our wok also revealed that the corn smut fungus makes its own version of plant hormones which it releases to change the structure and physiology of the corn plant. Corn smut disease includes the fungus causing the corn cells to divide and form a tumor in which the fungus grows, and then redirecting plant made nutrients to this tumor. Basically, the fungus tricks the plant into providing it with food and a place to live. We are working on understanding how and when the smut makes plant hormones, and also on how the fungal plant hormones change the plant. Finally we discovered something quite different when we were investigating the sequence of this organism's genome. If you consider the genome the library of the cell and the genes are the books, the way the genome works is you copy the book to take it away. We discovered that many times two different copies of the book are made and that the two copies can stick together (these two copies represent the sense and antisense RNAs). It turns out that producing the second copy of the gene is used to control the reading of the first copy and we have learned that this control might be how the organisms determine if it will cause disease. Our investigations will test this idea. The results of the proposed research will increase our understanding of how fungi infect plants. This will allow us to devise novel ways to fight the smut and rust fungi, providing new tools in our battle to reduce disease, and giving us a more stable food supply.