Karpov Sergey A, Tcvetkova Victoria S, Mamkaeva Maria A, Torruella Guifré, Timpano Hélène, Moreira David, Mamanazarova Karomat S, López-García Purificación
Zoological Institute, Russian Academy of Sciences, St. Petersburg, 199034, Russia.
St. Petersburg State University, St. Petersburg, 199034, Russia.
J Eukaryot Microbiol. 2017 Mar;64(2):204-212. doi: 10.1111/jeu.12352. Epub 2016 Aug 23.
Aphelids are a poorly known group of parasitoids of algae that have raised considerable interest due to their pivotal phylogenetic position. Together with Cryptomycota and the highly derived Microsporidia, they have been recently re-classified as the Opisthosporidia, which constitute the sister group to the fungi within the Holomycota. Despite their huge diversity, as revealed by molecular environmental studies, and their phylogenetic interest, only three genera have been described (Aphelidium, Amoeboaphelidium, and Pseudaphelidium), from which 18S rRNA gene sequences exist only for Amoeboaphelidium and Aphelidium species. Here, we describe the life cycle and ultrastructure of a new representative of Aphelida, Paraphelidium tribonemae gen. et sp. nov., and provide the first 18S rRNA gene sequence obtained for this genus. Molecular phylogenetic analysis indicates that Paraphelidium is distantly related to both Aphelidium and Amoebaphelidium, highlighting the wide genetic diversity of aphelids. Paraphelidium tribonemae has amoeboflagellate zoospores containing a lipid-microbody complex, dictyosomes, and mitochondria with rhomboid cristae, which are also present in trophonts and plasmodia. The amoeboid trophont uses pseudopodia to feed from the host cytoplasm. Although genetically distinct, the genus Paraphelidium is morphologically indistinguishable from other aphelid genera and has zoospores able to produce lamellipodia with subfilopodia like those of Amoeboaphelidium.
隐真菌是一类鲜为人知的藻类寄生生物，因其关键的系统发育位置而引发了广泛关注。它们与壶菌门以及高度特化的微孢子虫一起，最近被重新归类为后鞭毛菌门，该门是真菌界内真菌的姐妹群。尽管分子环境研究揭示了它们具有巨大的多样性以及系统发育学意义，但目前仅描述了三个属（隐真菌属、变形隐真菌属和假隐真菌属），其中只有变形隐真菌属和隐真菌属物种有18S rRNA基因序列。在此，我们描述了隐真菌目的一个新代表——三角褐指藻隐真菌属（Paraphelidium tribonemae）的生命周期和超微结构，并提供了该属的首个18S rRNA基因序列。分子系统发育分析表明，三角褐指藻隐真菌属与隐真菌属和变形隐真菌属的亲缘关系都较远，凸显了隐真菌的广泛遗传多样性。三角褐指藻隐真菌属具有含脂质微体复合物、高尔基体和具菱形嵴线粒体的变形鞭毛游动孢子，在滋养体和原质团中也存在这些结构。变形虫状的滋养体利用伪足从宿主细胞质中获取营养。尽管在基因上有差异，但三角褐指藻隐真菌属在形态上与其他隐真菌属无法区分，并且具有能够产生带有亚丝状伪足的片状伪足的游动孢子，类似于变形隐真菌属的游动孢子。
