Taxonomic revision of the genus Zygorhizidium: Zygorhizidiales and Zygophlyctidales ord. nov. (Chytridiomycetes, Chytridiomycota)
Taxonomic revision of the genus Zygorhizidium: Zygorhizidiales and Zygophlyctidales ord. nov. (Chytridiomycetes, Chytridiomycota)
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DOI：
10.3114/fuse.2020.05.02
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
K. Seto;K. Seto;K. Seto;S. D. Wyngaert;Yousuke Degawa;Maiko Kagami;Maiko Kagami
中科院分区：
文献类型：
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作者：
K. Seto;K. Seto;K. Seto;S. D. Wyngaert;Yousuke Degawa;Maiko Kagami;Maiko Kagami
在过去的十年里，基于游动孢子超微结构和分子系统学的分类系统发生了巨大的变化。与广泛研究的营养腐生类相比，到目前为止，大多数寄生类只能通过光学显微镜进行形态描述，因此它们在填补当前分类中存在的一些空白方面具有巨大的潜力。Zygorhizdium属的特征是有盖游动孢子囊和休眠孢子，这是有性繁殖的结果，其中雄体和雌体通过接合管融合。所描述的所有种都是藻类的寄生虫，它们的分类位置尚待确定。在这里，我们研究了7种Zygorhizdium spp.的形态、游动孢子超微结构、寄主专一性和分子系统发育。根据菌体形态和寄主专一性，鉴定出1株寄生在合藻绿藻上的菌落为威雷Z.willei，另1株为寄生在海藻上的硅藻Z.Asterion ellae，寄生在Aulacoseira上的Z.melosirae，寄生在Ulnaria(原针杆藻门)上的Z.Plattonicum。根据系统发育分析，Zygorhizdium被划分为两个不同的阶级级新谱系，一个谱系由该属的模式种Z.willei单独组成，另一个谱系包括三种硅藻寄生虫。游动孢子的超微结构观察表明，这两个谱系可以相互区分，在合胞菌目中都具有独特的特征。在这些结果的基础上，我们将三种硅藻寄生虫Zygphlyctis归入不同的Zygphlyctis属，并提出两个新目：Zygorhizidices和Zygphlyctidales。
During the last decade, the classification system of chytrids has dramatically changed based on zoospore ultrastructure and molecular phylogeny. In contrast to well-studied saprotrophic chytrids, most parasitic chytrids have thus far been only morphologically described by light microscopy, hence they hold great potential for filling some of the existing gaps in the current classification of chytrids. The genus Zygorhizidium is characterized by an operculate zoosporangium and a resting spore formed as a result of sexual reproduction in which a male thallus and female thallus fuse via a conjugation tube. All described species of Zygorhizidium are parasites of algae and their taxonomic positions remain to be resolved. Here, we examined morphology, zoospore ultrastructure, host specificity, and molecular phylogeny of seven cultures of Zygorhizidium spp. Based on thallus morphology and host specificity, one culture was identified as Z. willei parasitic on zygnematophycean green algae, whereas the others were identified as parasites of diatoms, Z. asterionellae on Asterionella, Z. melosirae on Aulacoseira, and Z. planktonicum on Ulnaria (formerly Synedra). According to phylogenetic analysis, Zygorhizidium was separated into two distinct order-level novel lineages; one lineage was composed singly of Z. willei, which is the type species of the genus, and the other included the three species of diatom parasites. Zoospore ultrastructural observation revealed that the two lineages can be distinguished from each other and both possess unique characters among the known orders within the Chytridiomycetes. Based on these results, we accommodate the three diatom parasites, Z. asterionellae, Z. melosirae, and Z. planktonicum in the distinct genus Zygophlyctis, and propose two new orders: Zygorhizidiales and Zygophlyctidales.