Department of Molecular, Cellular, & Biomedical Sciences, University of New Hampshire.
Department of Bioagricultural Sciences and Pest Management, Colorado State University.
Genome Biol Evol. 2017 Dec 1;9(12):3312-3327. doi: 10.1093/gbe/evx242.
Geosmithia morbida is an emerging fungal pathogen which serves as a model for examining the evolutionary processes behind pathogenicity because it is one of two known pathogens within a genus of mostly saprophytic, beetle-associated, fungi. This pathogen causes thousand cankers disease in black walnut trees and is vectored into the host via the walnut twig beetle. Geosmithia morbida was first detected in western United States and currently threatens the timber industry concentrated in eastern United States. We sequenced the genomes of G. morbida in a previous study and two nonpathogenic Geosmithia species in this work and compared these species to other fungal pathogens and nonpathogens to identify genes under positive selection in G. morbida that may be associated with pathogenicity. Geosmithia morbida possesses one of the smallest genomes among the fungal species observed in this study, and one of the smallest fungal pathogen genomes to date. The enzymatic profile in this pathogen is very similar to its nonpathogenic relatives. Our findings indicate that genome reduction or retention of a smaller genome may be an important adaptative force during the evolution of a specialized lifestyle in fungal species that occupy a specificniche, such as beetle vectored tree pathogens. We also present potential genes under selection in G. morbida that could be important for adaptation to a pathogenic lifestyle.
软腐 Geosmithia 是一种新兴的真菌病原体，是研究致病背后进化过程的模型，因为它是两个已知病原体中的一个，这两个病原体都属于以腐生、与甲虫有关的真菌属。这种病原体导致黑胡桃树上的千疮百孔病，并通过胡桃枝小蠹传播到宿主。软腐 Geosmithia 最初在美国西部被发现，目前威胁着集中在美国东部的木材工业。我们在之前的研究中对 G. morbida 的基因组进行了测序，在这项工作中对两种非致病性 Geosmithia 物种进行了测序，并将这些物种与其他真菌病原体和非病原体进行了比较，以确定 G. morbida 中与致病性相关的正选择基因。软腐 Geosmithia 在本研究观察到的真菌物种中拥有最小的基因组之一，也是迄今为止最小的真菌病原体基因组之一。该病原体的酶谱与非致病性亲缘物种非常相似。我们的研究结果表明，在专门化生活方式的进化过程中，基因组的减少或保留较小的基因组可能是一种重要的适应力量，这种专门化生活方式存在于占据特定生态位的真菌物种中，例如以甲虫为媒介的树病原体。我们还提出了软腐 Geosmithia 中受选择的潜在基因，这些基因可能对适应致病生活方式很重要。
