Trans-Species Polymorphism in Mitochondrial Genome of Camarodont Sea Urchins

Abstract

Mitochondrial (mt) genomes of the sea urchins Strongylocentrotus intermedius and Mesocentrotus nudus demonstrate the identical patterns of intraspecific length variability of the ND6 gene, consisting of 489 bp (S variant) and 498 bp (L variant), respectively. For both species, the ND6 length difference is due to the 488A>G substitution, which changes the stop codon TAG in S variant for a tryptophan codon TGG in L variant and elongates the corresponding ND6 protein by three additional amino acids, Trp-Leu-Trp. The phylogenetic analysis based on mt genomes of sea urchins and related echinoderm groups from GenBank has shown the S and L ND6 variants as shared among the camarodont sea urchins; the rest of the echinoderms demonstrate the S variant only. The data suggest that the ND6 488A>G substitution can be the first example of the trans-species polymorphism in sea urchins, persisting at least since the time of the Odontophora diversification at the Eocene/Oligocene boundary (approximately 34 million years ago), which was characterized by an abrupt climate change and significant global ocean cooling. Alternative hypotheses, including the convergent RNA editing and/or codon reassignment, are not supported by direct comparisons of the ND6 gene sequences with the corresponding transcripts using the basic local alignment search tool (BLAST) of full sea urchin transcriptomes.

Complete Mitochondrial Genomes and Phylogenetic Analysis of Genus Henricia (Asteroidea: Spinulosida: Echinasteridae)

“…The class Asteroidea de Blainville, 1830 (sea stars), belonging to the phylum Echinodermata Klein, 1778, represents the second most diverse class in this phylum, encompassing 1800 species categorized into 38 families [ 5 ]. These intriguing creatures inhabit oceans worldwide, with tropical Atlantic and Indo-Pacific regions showcasing the highest diversity across various depths [ 6 ]. Asteroids have garnered significant attention due to their unique chemical structures, particularly their steroid metabolites, which offer rich opportunities for exploration.…”