Host-parasite interaction in the endobiotic basal fungal lineage Nephridiophagidae and its insect host

大多数真菌门都含有不同程度特异性的昆虫病原谱系。一个高度专业化但很少被研究的群体是单细胞吞肾菌，这是一种感染昆虫马氏管的内生真菌。在这里，我们想要调查它们对宿主健康的影响。我们的假设是，受肾噬菌感染的宿主的适合性降低。将测试不同的健康成分，包括生殖成功、身体健康和生理健康相关因素，如免疫能力、马氏管功能和对化学杀虫剂的敏感性。德国小蟑螂是我们实验的理想测试生物体。对鸡蛋盒进行无菌清洗，能够产生无寄生虫的种群，这些种群可以通过喂养寄生的马氏小管而特别感染吞噬肾虫。此外，短的发育时间和快速的繁殖确保了足够数量的动物的生产。这也为有关人口发展和生殖成功的实验提供了便利。在第二部分中，我们想要揭开内生生物的生命周期，并建立系统发育关系。从口服吞噬丝虫孢子发育而来的早期生活期是完全未知的。我们假设孵化出的孢子体是能动的，并活跃地通过肠壁和血淋巴感染最终的栖息地，即马氏管。使用不同的物理和化学刺激进行体外实验，以诱导从孢子中孵化出孢子质。通过光学显微镜(例如，延时视频显微镜、细胞骨架的荧光免疫染色)观察运动的各个方面。早期原位发育将在口腔感染或将孢子注射到血淋巴后进行研究(例如，荧光染色的整装肠道准备，用于检测少量肾噬菌的聚合酶链式反应)。进一步的重点是深化吞肾菌科的分子系统学研究，以便找到早期分叉真菌群的确切位置。最近的研究结果支持，吞噬肾菌可能代表了一个新的基础真菌门，该门与合孢菌门S.l。为了更好地重建系统发育树，有必要分析更多的噬肾类物种，并使用更多的遗传标记。

Most fungal phyla contain entomopathogenic lineages with different degrees of specificity. A highly specialized but hardly studied group are the unicellular nephridiophagids, endobiotic fungi that infect the Malpighian tubules of insects. Here we want to investigate their effect on the fitness of their hosts. Our hypothesis is that the fitness of Nephridiophaga-infected hosts is reduced. Different fitness components will be tested, including reproductive success, physical fitness, and physiological fitness correlates such as immunocompetence, functionality of the Malpighian tubules, and susceptibility to chemical insecticides. The German cockroach Blattella germanica is an ideal test organism for our experiments. Sterile washing of the egg-cases enables production of parasite-free populations which can be specifically infected with Nephridiophaga by feeding parasitized Malpighian tubules. Further, the short development time and quick reproduction ensures the production of sufficient numbers of animals. This also facilitates experiments concerning population development and reproductive success. In a second part we want to unravel the life cycle of the endobionts and also establish the phylogenetic relationships. The early life stages which develop from orally ingested spores of Nephridiophaga are completely unknown. We hypothesize that the hatched sporoplasms are motile and actively pass through the gut wall and haemolymph to infect the final habitat, i.e. the Malpighian tubules. In-vitro experiments using different physical and chemical stimuli will be performed to induce hatching of the sporoplasm from the spore. Aspects of motility are observed by light microscopy (e.g. time lapse video microscopy, fluorescence immune staining of cytoskeleton). The early in-situ development will be studied after oral infection or after injection of spores into the haemolymph (e.g. whole mount gut preparations with fluorescent stains, PCR for detection of low numbers of Nephridiophaga). A further point of emphasis is to deepen the molecular phylogenetic studies of nephridiophagids in order to find the exact position within the early diverging fungal groups. Recent results support that nephridiophagids may represent a new basal fungal phylum close to the Chytridiomycota s.l. For a well-supported reconstruction of the phylogenetic tree it is necessary to analyze more nephridiophagid species and use more genetic markers.