Phylogenomics of a new fungal phylum reveals multiple waves of reductive evolution across Holomycota

Guest post by Luis Javier Galindo (@Luisjagago)

Hi, I am here to spread the news about the new phylum of fungi: Sanchytriomycota! You can read about it in our new publication in Nature Communications.

We introduce Sanchytriomycota, a new fungal phylum with some unique characteristics:

Flagellated zoospores that do not swim

Reduced flagellar machinery

Thanks to previous ultrastructural studies we knew that the sanchytrid flagellum was structurally reduced, so we decided to confirm if this reduction was reflected in their genome, and boy it was!

Reduced metabolism

Beside their small genomes, analyses based on the presence/absence of primary metabolism genes did not group sanchytrids with canonical fungi, but with non-fungal parasites that show evidence of reductive genome evolution.

A light sensing mechanism

We found the fusion protein BeGC1 in sanchytrids (involved in phototactic responses in Blastocladiella emersonii). Thus, an exaptation of the flagellar function towards a phototactic response could explaining its maintenance.

A new phylum

All these unique characteristics plus their phylogenetic position justify the creation of a new fungal phylum: Sanchytriomycota. By the way, chytrids or Blastocladiomycota first? See our take on it here:

Additionally, we addressed the evolution of hyphae in Holomycota and found that most of the hyphal morphogenesis gene repertoire of multicellular fungi had already evolved in early holomycotan lineages.

I would like to thank all co-authors for this massive work of 3+ years in the DEEM Team (@DEEMteam_Orsay). It took long, we struggled, but we made it!