EF: Ecological Genetics of Host-Specific Species Formation

宿主特异性物种形成的生态遗传学威廉·t·斯塔默和斯科特·e·厄德曼锡拉丘兹大学这项研究的中心目标是将生态学和微生物遗传学的知识整合到一个单一的系统中，以了解新物种形成的机制。该项目将重点研究真菌物种形成机制，并以索诺兰沙漠中生活在不同类型柱状仙人掌中的两种密切相关的酵母物种为目标。这两种酵母属于毕赤酵母（Pichia amethionina）复合体，只生活在仙人掌腐烂的茎中，与其他仙人掌特有的酵母和果蝇有着密切的生态联系。两种类型的仙人掌（窄心仙人掌和厚心仙人掌）在茎化学上彼此不同。早期的研究表明，一种以三萜苷形式存在的丰富的天然产物只存在于仙人掌中，它抑制了一种酵母的生长，从而阻止了它在仙人掌中生长。遗传学研究表明，这种抑制作用是由于两种仙人掌栖息酵母物种之间至少有一个基因差异。该项目利用普通面包酵母的全基因组敲除文库来鉴定和研究可能与Pichia amethionina复合体中负责物种多样化的仙人掌酵母基因相同的候选基因。一般来说，在全基因组中鉴定候选基因，提供了酵母在受到寄主化学物质挑战时潜在生理功能的信息，从而概述了酵母在自然环境中所经历的潜在细胞效应。研究分为四个阶段：1)对所有能提供对三萜苷抗性的基因进行分类。这项工作将利用现代酵母遗传工具和酿酒酵母基因组学知识来完成。2)确定目录中的哪些基因可以赋予仙人掌酵母抗性。这项工作将利用插入诱变和表达载体作为工具。3)确定哪些基因在自然界中确实具有抗药性。这项工作将使用实地调查和标准的实验室遗传杂交来找到实际负责的基因。4)发现将可能的解决方案限制在自然界中找到的实际解决方案的生态原因（限制和约束）。在实验室中使用仙人掌组织、果蝇和相关酵母进行生态实验，将用于寻找导致实际解决方案和多样化的生态学和遗传学之间的联系。这个项目将对我们理解新物种形成的基本过程具有重要意义。详细的分子机制与生态约束将提供一个独特的观点，微生物如何适应新的和外来的化学物质在其自然环境中，为什么一些遗传解决方案被更频繁地或优先使用相对于其他。

Ecological Genetics of Host-Specific Species FormationWilliam T. Starmer and Scott E. ErdmanSyracuse UniversityThe central goal of the research is to integrate knowledge of the ecology and genetics of microorganisms in a single system to understand the mechanisms responsible for formation of new species. The project will focus on fungal speciation mechanisms and target two closely related yeast species that live in different types of columnar cacti in the Sonoran Desert. The two yeasts, within the Pichia amethionina complex, only live in rotting stems of cacti and have close ecological associations with other cactus-specific yeasts and drosophila. The two cactus types (Stenocereus and Pachycereus) differ from one another in their stem chemistry. Earlier investigations have demonstrated that an abundant natural product in the form of a triterpene glycoside is found only in Stenocereus species and inhibits growth of one of the yeast species, thus preventing it from growing in that cactus. Genetic studies have shown the inhibition to be due to at least one gene difference between the two cactus dwelling yeast species. A genome-wide knockout library of the common baker's yeast Saccharomyces cerevisae is being employed by this project to identify and study candidate genes that may be identical to the cactus-yeast genes responsible for the species diversification in the Pichia amethionina complex. In general, identification of candidate genes, in the whole genome, provides information on potential physiological function when challenged with the host chemicals and thus an overview of potential cellular effects experienced by the yeast in the natural environment.There are four phases of the research: 1) Catalog all genes that can provide resistance to the triterpene glycosides. This work will be done using modern yeast genetic tools and knowledge of the genomics of S. cerevisae. 2) Determine which genes in the catalog can confer resistance in the cactus-yeast. This work will utilize insertional mutagenesis and expression vectors as tools. 3) Determine which genes that can confer resistance actually do confer resistance in nature. This work will use field surveys and standard laboratory genetic crosses to find the actual genes responsible. 4) Discover the ecological reasons (limits and constraints) that restrict the possible solutions to the actual solutions found in nature. Ecological experimentation in the laboratory using cactus tissue, drosophila, and associated yeasts will be used to find the connection between the ecology and genetics responsible for the actual solution and diversification.The project will be significant to our understanding of fundamental processes involved in the formation of new species. Detailed molecular mechanisms in relation to ecological constraints will provide a unique view of how microorganisms adapt to novel and exotic chemicals in their natural environment and why some genetic solutions are employed more frequently or with preference relative to others.