Exploration of Immune repertoire in the chromosome-level genome of the ctenophore Mnemiopsis Leidyi. Mnemiopsis leidyi chromosome-level genome assembly

In this study, we generated for first time a chromosome level genome for the ctenophore Mnemiopsis leidyi in order to explore its immune repertoire. We found that M. leidyi has a large range of the pfam domains that characterise common immune genes, in large expansions and with novel combinations of domain architectures. We extensively studied four families of common domains, the TIR2 domain which is component of Toll-like Receptors (TLR), the NACHT domain which is component of the NOD-like Receptors (NLR), the C-type Lectin and the Scavernger Receptor (SR) domains. We also studied the expression of those domains after experimental analysis of exposure of the host to a pathogen bacterium Vibrio coralliticus. We identified a very large expansion of those domains. The phylogeny of TIR2 domain indicated that M. leidyi has a large variety of TIR2 containing sequences but none of those is homologue to TLR or Myd88 sequences. Furthermore, it seems that M. leidyi has a bona fide NLR domain according to the domain architecture, and several types or SRCR and CTL sequences. The expression of several genes after exposure of the host with the pathogen V. coralliticus showed that these genes have a role in host-microbe interaction and immunity of the host.