Demystifying the functions of the mitochondrial ORFan proteins in bivalves with doubly uniparental inheritance.

Strict maternal inheritance of mitochondria is known to be the rule in animals, but over 100 species across six orders of bivalves possess doubly uniparental inheritance (DUI) of mitochondria. Under DUI, two distinctive sex-specific mitogenomes coexist. In marine and freshwater mussels, each mitogenome has an additional protein-coding gene, called female- and male-specific open reading frame or and , respectively.

Validation of the male-specific ORF of the paternally-transmitted mtDNA in Mytilus edulis as a protein-coding gene.

There appears to be an additional set of sex-specific mtDNA-encoded proteins in bivalve species with doubly uniparental mitochondrial inheritance that may be involved in the transmission of the female and male mitogenomes. In the marine mussel Mytilus edulis, the translation of the female-specific open reading frame (F-ORF) was demonstrated but the translation of the male-specific ORF (M-ORF) remains to be shown. Here we validate the male-specific ORF of the paternal mitogenome in M.