First insight into metal binding proteins from the de novo transcriptome of acanthocephalan parasite Dentitruncus truttae.

Acanthocephala are parasites increasingly used as bioindicators of environmental quality due to their ability to effectively accumulate metals. However, the mechanisms of metal homeostasis in them remain unclear as there has been only one genomic study on Acanthocephala species (Pomphorhynchus laevis). In the present study, the transcriptome of the freshwater acanthocephalan Dentitruncus truttae was assembled de novo and analyzed for orthologs and metal-binding proteins (MBPs), which were compared between two acanthocephalans and taxa related to them phylogenetically or by lifestyle. MBPs were characterized using the PFAM database and the MeBiPred software. Orthology analysis revealed that 75% of orthogroups were species-specific, with D. truttae sharing most orthologues (21% of non-species-specific) with P. laevis. The proteome of D. truttae consisted of 14.5% MBPs, predominantly zinc-binding proteins such as zinc finger proteins. Phylogenetic analysis of metalloproteases (zinc-binding), iron-sulphur protein group (iron-binding) and nickel-binding ureases/hydrogenases showed that the analyzed sequences are fairly conserved across all taxonomic groups, with a particularly high conservation in Acanthocephala and Rotifera. Protein sequences that could not be described using the PFAM database were grouped into three clusters characterized by a high preference for binding zinc and copper. This study provides the first transcriptomic insights into D. truttae and its MBPs, contributing to future research of the molecular mechanisms underlying metal accumulation in acanthocephalans. These findings may highlight their potential as bioindicators, reveal mechanisms of tolerance to toxic metals, and improve our understanding of their ecological adaptations and roles in aquatic ecosystems.