Caetano-Anollés G, Trigiano R N, Windham M T
Department of Biology, University of Oslo, Blindern, Norway.
Curr Genet. 2001 Jul;39(5-6):346-54. doi: 10.1007/s002940100223.
The anthracnose epidemic caused by exotic filamentous fungi of the genus Discula threatens the future of the prized flowering (Cornus florida L.) and Pacific (C. nuttalli Aud.) dogwoods in North America. A cross-section of fungi that cause anthracnose in broadleaf temperate trees was characterized using DNA amplification fingerprinting, sequence and secondary structure analysis of the internal transcribed spacers (ITS) of nuclear ribosomal DNA (rDNA), and compatibility of hyphal anastomosis. ITS-inferred phylogenies rejected the null hypothesis of only one fungal lineage, by defining four monophyletic and well differentiated groups, corresponding to Discula sp., D. quercina, D. umbrinella and D. destructiva, with the last two species sharing a common and recent ancestor. In turn, they showed that the dogwood pathogen, D. destructiva, did not evolve directly from an indigenous population related to Discula sp. In this study, rDNA spacers that are generally considered important for protein synthesis but are selectively neutral, appeared functionally constrained and subject to selective sequence diversification. Results confirmed the high variability of D. umbrinella and the remarkable homogeneity and exotic nature of D. destructiva at the genetic level, clarified the taxonomy and phylogeny of Discula, and provided clues as to the origin and diversification of dogwood anthracnose-causing fungi.
由盘多毛孢属外来丝状真菌引起的炭疽病流行，威胁着北美珍贵的开花山茱萸（弗吉尼亚山茱萸）和太平洋山茱萸（纳氏山茱萸）的未来。利用DNA扩增指纹图谱、核糖体DNA（rDNA）内转录间隔区（ITS）的序列和二级结构分析以及菌丝融合的兼容性，对导致阔叶温带树木炭疽病的真菌进行了横断面特征分析。ITS推断的系统发育通过定义四个单系且分化良好的类群，对应于盘多毛孢属菌、栎盘多毛孢、阴暗盘多毛孢和毁灭盘多毛孢，否定了只有一个真菌谱系的零假设，后两个物种有一个共同且最近的祖先。反过来，它们表明山茱萸病原体毁灭盘多毛孢并非直接从与盘多毛孢属菌相关的本地种群进化而来。在本研究中，通常被认为对蛋白质合成很重要但具有选择中性的rDNA间隔区，似乎在功能上受到限制且经历了选择性序列多样化。结果证实了阴暗盘多毛孢的高变异性以及毁灭盘多毛孢在遗传水平上显著的同质性和外来性质，阐明了盘多毛孢属的分类和系统发育，并为山茱萸炭疽病致病真菌的起源和多样化提供了线索。
