Relative quantification of the M and F mitochondrial DNA types in the blue mussel Mytilus edulis by real-time PCR

Abstract

Doubly uniparental inheritance (DUI) is an exceptional mode of mitochondrial DNA (mtDNA) transmission that has been reported in some bivalve species. In species with DUI there are two types of mtDNA, one being transmitted from the female parent to both daughters and sons through the egg (F type), and the other being transmitted from the male parent to sons only through the sperm (M type). Females are normally homoplasmic, having the F type in somatic tissues and eggs, whereas in males both the F and M types are found in the somatic tissues, but the M type is the exclusive type in spermatozoa. However, since the early description of DUI, the M type has been detected in the somatic tissue of females. In a recent study, the M type was detected in all Mytilus galloprovincialis females analysed. We describe here a real-time PCR assay for relative quantification of F and M types in the adductor muscle of M. edulis males and females. Dissociation curve analysis showed a single peak for the F and M primer pairs. The quantitative real-time PCR (qPCR) assay had a mean inter- and intraassay coefficient of variation of ,5%. We observed that in the majority of M. edulis females (75%) the M type is absent in the adductor muscle and when present it is in low amounts. The M/F ratio in the adductor muscle of M. edulis females ranged from 0.00002 and 0.00005, whereas in M. edulis males the M/F ratio ranged from 0.005 to 1.667. The qPCR assay developed in the present study may be used for the relative quantification of the M and F types in M. edulis from the East Atlantic region, but may also be used in M. galloprovincialis from the same region.