Systematics and Evolution of Cenococcum Geophilum Fr.: An Old Asexual Lineage?

9318119泰勒 DNA分析的分子方法，包括核苷酸测序和限制性内切酶图谱，正在彻底改变真菌进化和分类学的研究。 最有问题的真菌群，即不进行减数分裂且不形成孢子的无性形式，尤其令人烦恼，因为传统上，孢子承载结构的形态特征一直被用作分类鉴定和分类的特征。 分子数据为这一难题提供了解决方案。 博士后助理Karen LoBuglio博士在加州大学伯克利分校的John Taylor博士的指导下，正在使用现代分子程序对这个问题进行新的攻击，强调着名的菌根真菌Cenococcum geophilum，它在世界各地都有发现，但从未有过孢子。 来自蛋白质和核核糖体DNA的数据将有助于确定该真菌在子囊菌谱系中最接近的活体系统发育亲属;在分子钟假设下，这些数据还将提示该分类群的起源时间。2分子数据还将表明该真菌的地方和区域种群内的遗传变异程度，从而测试隐藏的细胞重组过程是否可能在被认为是无性的、死胡同的生命模式中产生变异。 新的DNA为基础的数据，从一个广泛的，但无性的菌根真菌将有助于回答两个重要的问题：适当的分类和系统发育的位置Cenococcum geophilum和真菌的无性类群能够产生遗传变异的可能性，也许通过隐蔽的细胞重组过程。

9318119 Taylor Molecular methods of DNA analysis, including nucleotide sequencing and restriction enzyme mapping, are revolutionizing the study of fungal evolution and taxonomy. The most problematic groups of fungi, the asexual forms that do not undergo meiosis and do not form spores, are especially troublesome because it is morphological features of the spore-bearing structures that have traditionally served as characters for taxonomic identification and classification. Molecular data provide a solution to the dilemma. Postdoctoral associate Dr. Karen LoBuglio under the guidance of Dr. John Taylor at University of California-Berkeley is using modern molecular procedures in a novel attack on this problem, emphasizing the well-known mycorrhizal fungus Cenococcum geophilum, which has been found throughout the world but never with spores. Data from proteins and from nuclear ribosomal DNA will help determine the closest living phylogenetic relatives of this fungus in the ascomycete lineage; under molecular clock assumptions, these data will also suggest the time of origin of the taxon. Molecular data will also indicate the extent of genetic variation within local and regional populations of the fungus, and thereby test whether cryptic cellular processes of recombination might generate variation in what has been considered an asexual, dead-end mode of life. New DNA-based data from a widespread but asexual mycorrhizal fungus will help answer two important questions: the proper classification and phylogenetic position of Cenococcum geophilum and the possibility that asexual taxa of fungi are able to generate genetic variability, perhaps through cryptic cellular processes of recombination.