Expanding the Search for Sperm Transmission Elements in the Mitochondrial Genomes of Bivalve Mollusks
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Mitochondrial DNA inheritanceSperm transmission elementsBivalvesDUI
Stewart, D.T... [et al.]. Expanding the Search for Sperm Transmission Elements in the Mitochondrial Genomes of Bivalve Mollusks. Genes 2021, 12, 1211. [https://doi.org/10.3390/genes12081211]
SponsorshipNatural Sciences and Engineering Research Council of Canada (NSERC) 217175 435656; European Commission 713750; Region Provence-Alpes-Cote d'Azur; French National Research Agency (ANR) ANR- 11-IDEX-0001-02 NSERC CGS-D award; Killam Predoctoral Scholarship; NS Graduate Scholarship; Harrison McCain Visiting Professorship Award at Acadia University from the Harrison McCain Foundation
Doubly uniparental inheritance (DUI) of mitochondrial DNA (mtDNA) in bivalve mollusks is one of the most notable departures from the paradigm of strict maternal inheritance of mtDNA among metazoans. Recently, work on the Mediterranean mussel Mytilus galloprovincialis suggested that a nucleotide motif in the control region of this species, known as the sperm transmission element (STE), helps protect male-transmitted mitochondria from destruction during spermatogenesis. Subsequent studies found similar, yet divergent, STE motifs in other marine mussels. Here, we extend the in silico search for mtDNA signatures resembling known STEs. This search is carried out for the large unassigned regions of 157 complete mitochondrial genomes from within the Mytiloida, Veneroida, Unionoida, and Ostreoida bivalve orders. Based on a sliding window approach, we present evidence that there are additional putative STE signatures in the large unassigned regions of several marine clams and freshwater mussels with DUI. We discuss the implications of this finding for interpreting the origin of doubly uniparental inheritance in ancestral bivalve mollusks, as well as potential future in vitro and in silico studies that could further refine our understanding of the early evolution of this unusual system of mtDNA inheritance.