AUTHOR=Xiong Xiao , Geden Christopher J. , Bergstralh Dan T. , White Roxie L. , Werren John H. , Wang Xu 

TITLE=New insights into the genome and transmission of the microsporidian pathogen Nosema muscidifuracis

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1152586

DOI=10.3389/fmicb.2023.1152586

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p><italic>Nosema</italic> is a diverse genus of unicellular microsporidian parasites of insects and other arthropods. <italic>Nosema muscidifuracis</italic> infects parasitoid wasp species of <italic>Muscidifurax zaraptor</italic> and <italic>M. raptor</italic> (Hymenoptera: Pteromalidae), causing ~50% reduction in longevity and ~90% reduction in fecundity.</p></sec><sec><title>Methods and Results</title><p>Here, we report the first assembly of the <italic>N. muscidifuracis</italic> genome (14,397,169 bp in 28 contigs) of high continuity (contig N50 544.3 Kb) and completeness (BUSCO score 97.0%). A total of 2,782 protein-coding genes were annotated, with 66.2% of the genes having two copies and 24.0% of genes having three copies. These duplicated genes are highly similar, with a sequence identity of 99.3%. The complex pattern suggests extensive gene duplications and rearrangements across the genome. We annotated 57 rDNA loci, which are highly GC-rich (37%) in a GC-poor genome (25% genome average). <italic>Nosema</italic>-specific qPCR primer sets were designed based on 18S rDNA annotation as a diagnostic tool to determine its titer in host samples. We discovered high <italic>Nosema</italic> titers in <italic>Nosema</italic>-cured <italic>M. raptor</italic> and <italic>M. zaraptor</italic> using heat treatment in 2017 and 2019, suggesting that the remedy did not completely eliminate the <italic>Nosema</italic> infection. Cytogenetic analyses revealed heavy infections of <italic>N. muscidifuracis</italic> within the ovaries of <italic>M. raptor</italic> and <italic>M. zaraptor</italic>, consistent with the titer determined by qPCR and suggesting a heritable component of infection and per ovum vertical transmission.</p></sec><sec><title>Discussion</title><p>The parasitoids-<italic>Nosema</italic> system is laboratory tractable and, therefore, can serve as a model to inform future genome manipulations of <italic>Nosema</italic>-host system for investigations of Nosemosis.</p></sec>