A novel minicollagen gene links cnidarians and myxozoans

Jason W Holland, Beth Okamura, Hanna Hartikainen, Chris J Secombes

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)


Myxozoans are enigmatic endoparasitic organisms sharing morphological features with bilateria, protists and cnidarians. This, coupled with their highly divergent gene sequences, has greatly obscured their phylogenetic affinities. Here we report the sequencing and characterization of a minicollagen homologue (designated Tb-Ncol-1) in the myxozoan Tetracapsuloides bryosalmonae. Minicollagens are phylum-specific genes encoding cnidarian nematocyst proteins. Sequence analysis revealed a cysteine-rich domain (CRD) architecture and genomic organization similar to group 1 minicollagens. Homology modelling predicted similar three-dimensional structures to Hydra CRDs despite deviations from the canonical pattern of group 1 minicollagens. The discovery of this minicollagen gene strongly supports myxozoans as cnidarians that have radiated as endoparasites of freshwater, marine and terrestrial hosts. It also reveals novel protein sequence variation of relevance to understanding the evolution of nematocyst complexity, and indicates a molecular/morphological link between myxozoan polar capsules and cnidarian nematocysts. Our study is the first to illustrate the power of using genes related to a taxon-specific novelty for phylogenetic inference within the Metazoa, and it exemplifies how the evolutionary relationships of other metazoans characterized by extreme sequence divergence could be similarly resolved.
Original languageEnglish
Pages (from-to)546-553
Number of pages8
JournalProceedings of the Royal Society of London. B, Biological Sciences
Issue number1705
Early online date1 Sep 2010
Publication statusPublished - 11 Jan 2011


  • phylum-restricted gene
  • polar capsules
  • nematocysts
  • Tetracapsuloides bryosalmonae


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