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

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 the isolates from different places belong to S. tribonematis . Here, we present a new strain X-137 CCPP ZIN RAS of fresh-water S. tribonematis having a peculiar morphology and an unusual stage in the life cycle. Its zoospores have a kinetosome composed of 9 microtubular singlets along its whole length (1.2 μm) with the pseudocilium containing an axoneme of 4 microtubules and enable to form an extremely long posterior filopodium (up to 10 body lengths). The kinetosome develops from a centriole of the centrosomal apparatus in sporangium, while another 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 zoospore or gamete fusions . These findings expand our still poor knowledge on the cell structure and biology of Sanchytriomycota .