Pioneering post-genomics approaches for studying algal host-pathogen interactions, using the ectocarpus/eurychasma model.

就像人类一样，藻类也受到真菌、细菌或病毒引起的疾病的困扰。这对生态具有重要意义，因为整个种群可能会周期性地被大量灭绝，或者以各种其他方式受到影响。此外，海藻和我们一样，也有类似于我们免疫系统的防御系统，这些防御系统是在感染后产生反应的。在涉及的化合物中，有些可能从生物技术的角度显示出一些有用的特性。然而，很少有研究集中在藻类疾病上，关于这一主题的数据也很少。在过去的几年里，在大规模蛋白质和化学鉴定领域取得了重大的技术进步。此外，一种名为Ectocarpus的褐藻的完整DNA序列将很快被破译。这将是第一种完整遗传信息将被解密的海藻。由于这些进展，这些工具现在可以用以前无与伦比的有效方式解决藻类疾病问题。该项目旨在将这些技术结合起来，准确地确定当棕藻Etocarpus被一种名为Euryachma的类似真菌的致病微生物感染时会发生什么。首先，将对不同的Etocarpus菌株进行感染实验，以确定一种对该真菌敏感(即会严重患病)的菌株，以及另一种将具有抗药性的菌株。然后，通过比较这两种藻类之间的差异，就有可能确定哪些蛋白质和确切地说哪些化学物质对藻类抵抗真菌是重要的。这项拟议的研究将为未来比较藻类、动物和陆地植物如何防御感染奠定基础。从现有的研究中已经可以推断，藻类与它们有一些非常古老的防御机制，但也有一些特殊性。其中最广为人知的是卤代化合物的产生，这是挥发物的主要自然来源，有可能降解臭氧层。在病原体攻击下，外果皮中积累的碘和溴的去向将使用X射线吸收光谱进行监测，这是一种最近被适应于在海洋生物中研究这一问题的物理技术。此外，还将深入了解Euryachma攻击海藻的实际感染机制。由于这是主要致病的卵菌生物群中最原始的成员，这将更好地揭示他的同类中的其他成员，特别是一些具有重要经济意义的近亲感染农作物的感染策略，最明显的是葡萄和土豆上的霉菌。最后，由于真海藻不能在不感染海藻的情况下存活，它一定是与海藻一起进化得非常紧密的。通过对世界不同地区的真菌进行采样，并试图感染来自不同地理来源的大量藻类，我们将试图了解病原体和藻类可能是如何共同进化的。这种对藻类及其寄生虫生物多样性的了解也将有助于今后研究自然生境中的流行病，并评估它们在生态系统动态中的作用。

Just like humans, algae are plagued by diseases caused by fungi, bacteria or viruses. This is of ecological importance since entire populations can be periodically decimated, or impacted in a variety of other ways. Also seaweeds, like ourselves, have defenses resembling aspects of our immune system that are produced response to infection. Among the chemical compounds involved, some may display some useful properties from a biotechnological perspective. However, few studies have focused on algal diseases, and data on this topic are scarce. During the last few years, major technical improvements have been made in the field of large scale protein and chemical identification. Furthermore, the complete DNA sequence of a brown alga named Ectocarpus will soon be deciphered. This will be the very first seaweed of which the entire genetic information will be decrypted. Because of those advances, the tools are now available to address the question of algal diseases in a previously unequalled, efficient manner. This project aims to combine these techniques to determine precisely what happens when the brown alga Ectocarpus gets infected by a fungus-like disease-causing organism called Eurychasma. Firstly, infection experiments will be performed on different Ectocarpus strains in order to identify one that would be sensitive to the fungus (i.e. that would get seriously diseased), and another one that would be resistant. Then, by comparing the differences between those two algal strains, it will be possible to determine which proteins and exactly which chemical substances are important for the alga to be resistant against the fungus. The proposed research will contribute to a basis for future comparisons on how algae, animals and terrestrial plants defend themselves against infection. From the existing studies, it can already be inferred that algae share some very old defence mechanisms with them, but that they also have some particularities. Among those, the most widely known is the production of halogenated compounds which are the major natural source of volatiles with the potential to degrade the ozone layer. The fate of iodine and bromine accumulated in Ectocarpus under pathogen attack will be monitored using X-ray absorption spectroscopy, a physical technique that was recently adapted for studying such question in marine organisms. Also, there will be insight about the actual infection mechanism of Eurychasma attacking seaweeds. Since this is the most primitive member of this mostly pathogenic group of organisms, of the oomycetes, this will shed more light on the infection strategies shared by other members of his kind and particularly by some of its close relatives of great economic importance which infect crop plants, most notably the mildew on grape and potato. Finally, since Eurychasma cannot survive without infecting seaweeds, it must have evolved very closely together with these. By sampling the fungus in different parts of the world and trying to infect a large number of algae from different geographical origins, we will try to understand how the pathogen and the algae might possibly have co-evolved. This knowledge of the biological diversity of both the alga and its parasite will also be useful for future studies on epidemics in natural habitats and to assess their role in ecosystem dynamics.