Early expansion and expression of the lipopolysaccharide (LPS)-induced TNF-α factor (LITAF) gene family in the LPS-exposed monogonont rotifer Brachionus koreanus

To date, a single lipopolysaccharide-induced TNF-α factor (LITAF) homologue, mediating the expression of inflammatory cytokines including TNF-α in terms of host defense was identified in vertebrates and most invertebrates such as insects, mollusks, and crustaceans. However, LITAF gene family members have recently been characterized in only two mollusks, Crassostrea gigas and Mytilus galloprovincialis. Although a large gene family expansion of LITAF homologues was observed in the nematode Caenorhabditis elegans, the amino acid sequences encoded by the C. elegans LITAF homologue have low similarities to other LITAF gene family members. In this study, three LITAF genes were identified in the monogonont rotifer Brachionus koreanus. In silico analyses of B. koreanus LITAF genes of conserved domains and phylogenetic relationships supported gene annotations that indicated that LITAF is involved in innate immunity in primitive rotifers. To examine transcriptional sensitivity of B. koreanus LITAF genes, the rotifers were exposed to different concentrations of lipopolysaccharide (LPS). Transcriptional levels of LITAF1 and LITAF2 gene were significantly upregulated dose- and time-dependently in response to LPS exposure for 24 h. LPS exposure induced glutathione (GSH) depletion and antioxidant enzyme activity levels for 24 h in B. koreanus. These results suggested that the B. koreanus LITAF gene family has potential sensitivities directly and/or indirectly to immune stimulator-triggered oxidative stress.