Fungalpedia – Note 82 Sanchytriomycota
Sanchytriomycota Galindo, López-García, Torruella, Karpov & Moreira
Citation when using this entry: Wijayawardene et al., in prep – Fungalpedia, taxa of the basal fungi and fungus-like organisms. Mycosphere.
Sanchytrids are obligate parasitoids of freshwater algae and superficially resemble Chytridiomycetes. They have a rounded to elongated anatropous sporangium and unusual amoeboid zoospores with filopodia and posterior pseudocilium (reduced immotile flagellum). Currently, the phylum Sanchytriomycota comprises a single class (Sanchytriomycetes), one order (Sanchytriales) and one family (Sanchytriaceae). Two monotypic genera have been placed in Sanchytriomycota viz., Sanchytrium Karpov et al 2017 (type: Sanchytrium tribonematis fide Karpov et al. 2017) and Amoeboradix Karpov et al. (2017) (type species: Amoeboradix gromovii fide Karpov et al. 2018). However, Amoeboradix and Amoeboradix gromovii were invalid (Art. F.5.1, Shenzhen) but validated in Index Fungorum (2020).
Both Amoeboradix and Sanchytrium are closely related and formed a long branch among higher fungi on the 18S phylogenetic tree, sister to Glomeromycota (Karpov et al. 2018). However, in multigene phylogenetic analyses, these two genera formed a separate lineage sister to Blastocladiomycota (Galindo et al. 2021). Ultrastructural studies of their zoospores and sporangia revealed extreme peculiarities in both species. They have a highly reduced flagellar apparatus with a very long kinetosome (up to 1.5 µm) composed of 9 singlets (Sanchytrium) and singlets/doublets (Amoeboradix) of microtubules and the axoneme of just four microtubules supporting a thin immobile pseudocilium. The centrioles in sporangia are also composed of nine singlets (Karpov et al. 2017, 2018, 2019). Based on phylogenetic position and morphological peculiarities Amoeboradix and Sanchytrium were placed in the new phylum Sanchytriomycota (Galindo et al. 2021).
Type species: Sanchytrium tribonematis Karpov & Aleoshin
Figure 1 – Light microscopy observations of sanchytrid cells. a–e Life cycle stages of Sanchytrium tribonematis. f–j Life cycle stages of Amoeboradix gromovi. a–d, f–i Amoeboid crawling zoospores with filopodia (f) and posterior pseudocilium (pc). g–i Zoospores with retracted pseudocilium. e, j Sporangium (sp) with one (e) or two (j) papillae (p) on the host (h) surface. Scale bars: a-d, f-I = 5 µm; e, j = 10 µm.
Galindo LJ, López-García P, Torruella G, Karpov S, Moreira D. 2021 – Phylogenomics of a new fungal phylum reveals multiple waves of reductive evolution across Holomycota. Nature Communications 12, 4973.
Karpov SA, López-García P, Mamkaeva MA, Klimov VI et al. 2018 – The chytrid-like parasites of algae Amoeboradix gromovi gen. et sp. nov. and Sanchytrium tribonematis belong to a new fungal lineage. Protist 169, 122–140.
Karpov SA, Mamanazarova KS, Popova OV, Aleoshin VV et al. 2017 – Monoblepharidomycetes diversity includes new parasitic and saprotrophic species with highly intronized rDNA. Fungal Biology 121, 729–741.
Karpov SA, Vishnyakov AE, Moreira D, López‐García P. 2019 – The ultrastructure of Sanchytrium tribonematis (Sanchytriaceae, Fungi incertae sedis) confirms its close relationship to Amoeboradix. Journal of Eukaryotic Microbiology 66, 892–898.
Wijayawardene NN, Centre for Yunnan Plateau Biological Resources Protection and Utilization, College of Biological Resource and Food Engineering, Qujing Normal University, Qujing 655011, China, Karpov SA, Zoological Institute, Russian Academy of Sciences, St. Petersburg 199034, Russian Federation, Wimalasena SDMK, Faculty of Graduate Studies, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri Lanka
(Edited by Kevin D. Hyde)