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 (Δψm). Reflecting high functionality, elevated Δψm usually depicts healthy mitochondria and contributes to organelle selection. This study investigates whether mitochondrial properties linked with bioenergetics, such as Δψm, play a role in paternal inheritance of mitochondria. More specifically, the study looks at how sperm Δψm 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 Δψm 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 Δψm did not vary between the two groups. However, there was a trend of increase in Δψm following egg detection only in sperm bearing paternally derived mitochondria (DUI). This suggests, along with bioenergetic changes, that Δψm 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.