Twenty-five new microsporidian genomes: Insights into ploidy, reproduction, and the group's pangenome

Microsporidia are single-celled, intracellular parasites of growing interest. Despite their importance, their biology remains largely unknown, due to challenges in sampling, culturing, and manipulation. In a recent study, researchers generated 25 new microsporidian genomes from serendipitously infected organisms sequenced for biodiversity projects like the Darwin Tree of Life. The genomes include 14 biologically complete and 11 partial sequences.

Utilizing RNA-seq data from three previously published genomes, the team identified Prokka as an effective method for annotating Microsporidia genomes. By comparing gene content across different clades of microsporidia, researchers found a high level of diversity in the microsporidian pangenome, indicating that current genomic data does not fully represent the group's proteome.

Interestingly, GC content and genome span did not consistently correlate with the number of orthogroups across lineages, suggesting different evolutionary pressures at play. The study also revealed few one-to-one orthogroups, as well as few orthogroups that are both lineage-specific and conserved within a lineage. This diversity highlights the complexity of microsporidian evolution.

Additionally, Hi-C data confirmed that tetraploid Amblyosporida microsporidia function as two equivalent diploid units within the cell, whereas a tetraploid Enterocytozoonida genome suggests that all four genome copies reside in a single nucleus, supporting a previous hypothesis.