线粒体DNA序列多位点分析揭示全球松茸复合种种内有限基因变异和种间稳定区别

Mitochondrial Multilocus DNA Sequence Analyses Reveal Limited Genetic Variability Within and Consistent Differences Between Species of the Global Matsutake Species Complex

松茸是外生菌根真菌,分布在北半球,在温带生态系统的物质循环和改善植物健康中发挥着重要作用。这类食用菌也具有很高的经济价值,尤其在日本。根据形态特征和基于细胞核核糖体RNA基因簇转录间隔区(ITS)序列的DNA条形码,已经把松茸按不同地理区域来源归为几个物种:Tricholoma matsutake(欧亚大陆),T.anatolicum(地中海区域),T.magnivelare(北美东部),T.murrillianum(北美西部)和T.mesoamericanum(墨西哥)。这些物种共同构成全球松茸复合种。本研究通过多位点序列分析进一步调查松茸系统地理学,更深入的理解这种生物的全球分布和进化历史。来自北美、北欧和东亚的42个松茸样品的ITS序列和4个线粒体位点被检测。总体上线粒体DNA多位点系统分析呈现出和ITS系统发育分析一致的模式和拓扑结构,即各个地理区域的样品分别聚在一起。然而,在我们的4个被检测物种的样品间,几乎没有或没有发现所选线粒体位点的基因变异。我们的研究结果表明松茸物种复合体中的线粒体基因组的进化速度较慢,或各个物种的广泛分布源于近期的扩散。深入理解松茸复合种的遗传多样性和演化关系,对制定保护政策有重要意义。

Matsutake are ectomycorrhizal fungi that grow around the northern hemisphere where they play a crucial role in nutrient cycling and improving plant health within temperate ecosystems.These edible mushrooms also have high economic value,especially in Japan.Morphological characters and DNA barcoding,based on sequences of the nuclear internal transcribed spacer(ITS)regions of the ribosomal RNA gene cluster,have provided a basis for assigning matsutake from different geographical regions to several species:Tricholoma matsutake(Eurasia),T.anatolicum(Mediterranean),T.magnivelare(eastern Canada/USA),T.murrillianum(western Canada/USA)and T.mesoamericanum(Mexico).Together,these species constitute the global matsutake species complex.This study further examined the phylogeography of matsutake mushrooms through a multilocus sequence analysis to gain a more complete understanding of the global distribution and evolutionary history of these organisms.Sequences of the ITS and four mitochondrial loci were examined for 42 matsutake samples collected from North America,northern Europe and eastern Asia.Overall,the multilocus mitochondrial DNA phylogeny exhibits a pattern and topology consistent with that of the ITS phylogeny,with samples from each geographical region clustering together.However,little or no genetic variability was observed at the mitochondrial loci among samples from each of our four examined species.Our results suggest that either the mitochondrial genomes in the matsutake species complex have a slow rate of evolution or the broad distribution of each species is due to a recent range expansion.Having a strong understanding of the genetic diversity and evolutionary relationships among mushrooms within the matsutake species complex has important implications for informing conservation policies.