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Free keywords:
Parasites, Schistocephalus solidus; Cestodes;
Ecological genomics; Genomics/proteomics;
Molecular mimicry; Host-parasite interactions; Wnt; RT-PCR
Abstract:
Background
Endoparasites with complex life cycles are faced with several biological challenges, as they
need to occupy various ecological niches throughout their development. Host phenotypes that
increase the parasite’s transmission rate to the
next host have been extensively described, but
few mechanistic explanations have been proposed
to describe their proximate causes. In this
study we explore the possibility that host phenotypic changes are triggered by the production
of mimicry proteins from the parasite by using an ecological model system consisting of the
infection of the threespine stickleback (
Gasterosteus aculeatus
) by the cestode
Schistocephalus solidus
.
Method
Using RNA-seq data, we assembled 9,093 prot
ein-coding genes from which ORFs were
predicted to generate a reference proteome.
Based on a previously published method, we built
two complementary analysis pipelines to i) establish a general classification of protein
similarity among various species (pipeline A) and ii) identify candidate mimicry proteins
showing specific host-parasite
similarities (pipeline B), a key feature underlying the
possibility of molecular mimicry.
Results
Ninety-four tapeworm proteins showed high
local sequence homology with stickleback
proteins. Four of these candidates correspond to secreted or membrane proteins that could be
produced by the parasite and eventually be rele
ased in or be in contact with the host to
modulate physiological pathways involved in various phenotypes (e.g. behaviors). One of
these candidates belongs to the Wnt family, a large group of signaling molecules involved in
cell-to-cell interactions and various developmental pathways. The three other candidates are
involved in ion transport and post-translational protein modifications. We further confirmed
that these four candidates are expressed in thre
e different developmental stages of the cestode
by RT-PCR, including the stages found in the host.
Conclusion
In this study, we identified mimicry candida
te peptides from a behavior-altering cestode
showing specific sequence similarity with host proteins. Despite their potential role in
modulating host pathways that could lead to
parasite-induced phenotypic changes and despite
our confirmation that they are expressed in the developmental stage corresponding to the
altered host behavior, further investigations will
be needed to confirm their mechanistic role
in the molecular cross-talk taking place between
S. solidus
and the threespine stickleback.
