Presence of male mitochondria in somatic tissues and their functional importance at the whole animal level in the marine bivalve Arctica islandica

• Published in: Communications Biology
• Main Authors: Dégletagne, C., Abele, D., Glöckner, G., Alric, B., Gruber, H., Held, C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2021
• Subjects: Arctica islandica; Ocean quahog
• Online Access: http://hdl.handle.net/21.11116/0000-0009-4817-D; http://hdl.handle.net/21.11116/0000-0009-4819-B

Metazoans normally possess a single lineage of mitochondria inherited from the mother (♀-type mitochondria) while paternal mitochondria are absent or eliminated in fertilized eggs. In doubly uniparental inheritance (DUI), which is specific to the bivalve clade including the ocean quahog, Arctica islandica, ♂-type mitochondria are retained in male gonads and, in a few species, small proportions of ♂-type mitochondria co-exist with ♀-type in somatic tissues. To the best of our knowledge, we report, for the first time in metazoan, the natural occurrence of male and female individuals with exclusively ♂-type mitochondria in somatic tissues of the bivalve A. islandica. Mitochondrial genomes differ by ~5.5% at DNA sequence level. Exclusive presence of ♂-type mitochondria affects mitochondrial complexes partially encoded by mitochondrial genes and leads to a sharp drop in respiratory capacity. Through a combination of whole mitochondrial genome sequencing and molecular assays (gene presence and expression), we demonstrate that 1) 11% of individuals of an Icelandic population appear homoplasmic for ♂-type mitochondria in somatic tissues, 2) ♂-type mitochondrial genes are transcribed and 3) individuals with ♂-type mitochondria in somatic cells lose 30% of their wild-type respiratory capacity. This mitochondrial pattern in A. islandica is a special case of DUI, highlighted in individuals from both sexes with functional consequences at cellular and conceivably whole animal level.