Phylogeny and Phenotypic Characterization of Pathogenic Cryptococcus Species and Closely Related Saprobic Taxa in the Tremellales
Phylogeny and Phenotypic Characterization of Pathogenic Cryptococcus Species and Closely Related Saprobic Taxa in the Tremellales
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DOI：
10.1128/ec.00373-08
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发表时间：
2009-03-01
期刊：
影响因子：
--
通讯作者：
Heitman, Joseph
中科院分区：
文献类型：
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作者：
Findley, Keisha;Rodriguez-Carres, Marianela;Heitman, Joseph
新型隐球菌和格特隐球菌是引起人类和动物呼吸系统和神经系统疾病的密切相关的姊妹种。在这两个公认的物种中，系统发育分析揭示了至少六个被定义为分子类型（VNI/II/B、VNIV、VGI、VGII、VGIII和VGIV）的隐蔽物种，它们构成致病性隐球菌物种复合体。这些致病物种聚集在银耳目内的Filobasidiella分支中。以前的研究表明，Filobasidiella分支还包括几个从昆虫粪便中分离出的腐菌，但信息评估的相关性的saprobes和病原体在这个集群是有限的。在这里，包含一个子集的物种在银耳目谱系，集群密切与致病性隐球菌属物种复杂的系统发育，解决了采用多位点测序方法进行系统发育分析。从15个相关的担子菌物种的6个高度保守的基因组位点进行测序，并从串联的基因序列的比对与不同的树建设标准进行了评估。此外，这15个物种进行了毒力和表型测定，以评估其致病潜力。这些研究表明，淀粉隐球酵母和土屋菌是两个非致病性的姊妹种，是与病原体C.新型隐球菌和gattii和Filobasidielladepaerata一起形成严格意义上的隐球菌群。另外五种腐殖酵母形成了Kwoniella分支，这似乎是一个更远的相关广义组的一部分。这项研究为未来的比较基因组学方法奠定了基础，该方法将深入了解交配型位点的结构，功能和进化，有性生殖模式的转变，以及人类致病物种从相关或祖先的saprobic物种中的出现。
The basidiomycetous yeasts Cryptococcus neoformans and Cryptococcus gattii are closely related sibling species that cause respiratory and neurological disease in humans and animals. Within these two recognized species, phylogenetic analysis reveals at least six cryptic species defined as molecular types (VNI/II/B, VNIV, VGI, VGII, VGIII, and VGIV) that comprise the pathogenic Cryptococcus species complex. These pathogenic species are clustered in the Filobasidiella clade within the order Tremellales. Previous studies have shown that the Filobasidiella clade also includes several saprobic fungi isolated from insect frass, but information evaluating the relatedness of the saprobes and pathogens within this cluster is limited. Here, the phylogeny encompassing a subset of species in the Tremellales lineage that clusters closely with the pathogenic Cryptococcus species complex was resolved by employing a multilocus sequencing approach for phylogenetic analysis. Six highly conserved genomic loci from 15 related basidiomycete species were sequenced, and the alignments from the concatenated gene sequences were evaluated with different tree-building criteria. Furthermore, these 15 species were subjected to virulence and phenotype assays to evaluate their pathogenic potential. These studies revealed that Cryptococcus amylolentus and Tsuchiyaea wingfieldii, two nonpathogenic sibling species, are the taxa most closely related to the pathogens C. neoformans and C. gattii and together with Filobasidiella depauperata form a Cryptococcus sensu stricto group. Five other saprobic yeast species form the Kwoniella clade, which appears to be a part of a more distantly related sensu lato group. This study establishes a foundation for future comparative genomic approaches that will provide insight into the structure, function, and evolution of the mating type locus, the transitions in modes of sexual reproduction, and the emergence of human pathogenic species from related or ancestral saprobic species.