Investigating the role of mitochondrial membrane potential in paternal inheritance of mitochondria

The process of oxidative phosphorylation (OXPHOS) in mitochondria depends on an electrochemical gradient known as the mitochondrial membrane potential (Delta psi m). Reflecting high functionality, elevated Delta psi m usually depicts healthy mitochondria and contributes to organelle selection. This study investigates whether mitochondrial properties linked with bioenergetics, such as Delta psi m, play a role in paternal inheritance of mitochondria. More specifically, the study looks at how sperm Delta psi m responds to egg chemoattractants in bivalves characterized by distinct mitochondrial inheritance patterns: strict maternal inheritance (SMI) and doubly uniparental inheritance (DUI), the latter displaying sex-specific transmission of paternal mitochondrial DNA. Sperm Delta psi m was examined in four bivalve species: the blue mussel (Mytilus edulis) and the Manila clam (Ruditapes philippinarum) (DUI), plus the hard clam (Mercenaria mercenaria) and the soft-shell clam (Mya arenaria) (SMI). In the absence of egg chemoattractants, sperm Delta psi m did not vary between the two groups. However, there was a trend of increase in Delta psi m following egg detection only in sperm bearing paternally derived mitochondria (DUI). This suggests, along with bioenergetic changes, that Delta psi m modulation might be a specific property of at least some DUI species, possibly implicated in their unique ability to transmit their mitochondria in a sex-specific fashion.