A comprehensive phylogeny of Neurospora reveals a link between reproductive mode and molecular evolution in fungi
A comprehensive phylogeny of Neurospora reveals a link between reproductive mode and molecular evolution in fungi
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DOI：
10.1016/j.ympev.2011.03.023
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发表时间：
2011-06-01
影响因子：
4.1
通讯作者：
Johannesson, Hanna
中科院分区：
文献类型：
--
作者：
Nygren, Kristiina;Strandberg, Rebecka;Johannesson, Hanna
丝状子囊菌属包括具有广泛繁殖方式的分类群。该属的有性繁殖可分为三种主要方式：异型(自交不亲和)、同型(自交亲和)和假同型(部分自交)。除了有性途径外，大多数异株类群都以形态上不同的营养传播繁殖体(大分生孢子)繁殖，而在大多数同源类群中没有检测到这一特征。在这项研究中，我们使用了43个分类群中的7个核基因座的序列信息(301个可能的座位-分类群组合中的295个)来创建脉孢子菌的系统发育。结果表明，在这组真菌中，繁殖模式的转换发生了多次。虽然同源的祖先意味着生殖模式中的开关较少，但我们认为脉孢子菌的祖先可能是异源的，在该属的进化史上，同源至少进化了六次。此外，脉孢子菌的两个假同源分类群(四分孢菌和四分孢菌)代表了两个独立的来源。系统发育分支间替换率的似然比检验表明，繁殖方式是推动脉孢子虫基因组进化的重要因素。首先，在描述同源类群的分支中发现了更多的非同义/同义替换，这表明在这些类群中净化选择的效率降低。此外，与同源的非分生孢子谱系相比，在产生分生孢子的异株系中发现了更高的核苷酸替换率。后一种发现可能是由于分生孢子的存在，即较高的有丝分裂诱导突变的比率，和/或同源分类群进化出较低的突变率以避免基因组退化。(C)2011 Elsevier Inc.保留所有权利。
The filamentous ascomycete genus Neurospora encompasses taxa with a wide range of reproductive modes. Sexual reproduction in this genus can be divided into three major modes; heterothallism (self-incompatibility), homothallism (self-compatibility) and pseudohomothallism (partial self-compatibility). In addition to the sexual pathway, most of the heterothallic taxa propagate with morphologically distinct, vegetative dissemination propagules (macroconidia), while this feature is undetected in the majority of the homothallic taxa. In this study, we used sequence information of seven nuclear gene loci from 43 taxa (295 of the possible 301 locus-by-taxon combinations) to create a phylogeny of Neurospora. The results suggest that transitions in reproductive mode have occurred at multiple times within this group of fungi. Although a homothallic ancestor would imply fewer switches in reproductive mode, we argue that the ancestor of Neurospora was likely heterothallic and that homothallism has evolved independently at least six times in the evolutionary history of the genus. Furthermore, the two pseudohomothallic taxa of Neurospora (N. tetrasperma and N. tetraspora) represent two independent origins of pseudohomothallism. Likelihood ratio tests of substitution rates among branches in the phylogeny indicate that reproductive mode is an important factor driving genome evolution in Neurospora. First, an increased level of non-synonymous/synonymous substitutions in branches delineating homothallic taxa was found, suggesting a reduced efficiency of purifying selection in these taxa. Furthermore, elevated nucleotide substitution rates were found in heterothallic, conidia-producing, lineages as compared to the homothallic non-conidiating lineages. The latter finding is likely due to the presence of conidia, i.e., a higher rate of mitotic divisions inducing mutations, and/or that the homothallic taxa have evolved a lower mutation rate to avoid genomic degeneration. (C) 2011 Elsevier Inc. All rights reserved.