Sphaerospora molnari (Myxozoa) SMBS transcriptome data

Parasites employ proteases to evade host immune systems, feed and
replicate and are often the target of anti-parasite strategies to disrupt
these interactions. Myxozoans are obligate cnidarian parasites,
alternating between invertebrate and fish hosts. They are highly divergent
from other metazoans with regard to their gene sequences, and available
genomic and transcriptomic datasets are limited. Some myxozoans are
important aquaculture pathogens such as Sphaerospora molnari replicating
in the blood of farmed carp before reaching the gills for sporogenesis and
transmission. Proliferative stages cause a massive systemic lymphocyte
response and the disruption of the gill epithelia by spore-forming stages
leads to respiratory problems and mortalities. In the absence of
a S. molnari genome, we utilized a de
novo approach to assemble the first transcriptome of
proliferative myxozoan stages to identify S. molnari proteases that are
upregulated during the first stages of infection when the parasite
multiplies massively, rather than in late spore-forming plasmodia.
Furthermore, a subset of orthologs was used to characterize 3D structures
and putative druggable targets. An assembled and host filtered
transcriptome containing 9436 proteins, mapping to 29 560 contigs was
mined for protease virulence factors and revealed that cysteine proteases
were most common (38%), at a higher percentage than other myxozoans or
cnidarians (25-30%). Two cathepsin Ls that were found upregulated in
spore-forming stages with a presenilin like aspartic protease and a
dipeptidyl peptidase. We also identified downregulated proteases in the
spore-forming development when compared with proliferative stages
including an astacin metallopeptidase and lipases (qPCR). In total, 235
transcripts were identified as putative proteases using a MEROPS
database. In silico analysis of highly transcribed
cathepsins revealed potential drug targets within this data set that
should be prioritised for development. In silico surveys for proteins are
essential in drug discovery and understanding host-parasite interactions
in non-model systems. The present study of S. molnari’s protease arsenal
reveals previously unknown proteases potentially used for host
exploitation and immune evasion. The pioneering dataset serves as a model
for myxozoan virulence research, which is of particular importance as
myxozoan diseases have recently been shown to emerge and expand
geographically, due to climate change.