Study of new strain of Sanchytrium tribonematis expands our knowledge on Sanchytriomycota (Fungi)

Abstract Recently, phylogenomic analyses of two parasitic fungi with amoeboid zoospores and long kinetosomes, the sanchytrids Amoeboradix gromovi and Sanchytrium tribonematis, showed that they formed a clade Sanchytriomycota sister to Blastocladiomycota. Sanchytrid species diversity is still very low and most of isolates from different places belong to S. tribonematis. Here, we present a new strain X-137 of fresh-water S. tribonematis having peculiar morphology and unusual stage in the life cycle. Its zoospores have kinetosome composed by 9 microtubular singlets along its whole length (1.2 µm) with pseudocilium containing axoneme of 4 microtubules, and enable to form extremely long posterior filopodium (up to 10 body lengths). Kinetosome develops from the mother centriole of centrosomal apparatus of sporangium, while daughter centriole becomes a non-flagellar kinetosome. Big zoospores with several pseudocilia and many (up to eleven) kinetosomes per cell have been found in S. tribonematis culture. They are probably a result of several zoospores or gametes fusion. These findings expand our still poor knowledge on the cell structure and biology of Sanchytriomycota.