Expression of M6 and M7 lysin in Mytilus edulis is not restricted to sperm, but occurs also in oocytes and somatic tissue of males and females

Abstract

Sperm proteins of marine sessile invertebrates have been extensively studied to understand the molecular basis of reproductive isolation. Apart from molecules such as bindin of sea urchins or lysin of abalone species, the acrosomal protein M7 lysin of Mytilus edulis has been analyzed. M7 lysin was found to be under positive selection, but mechanisms driving the evolution of this protein are not fully understood. To explore functional aspects, this study investigated the protein expression pattern of M7 and M6 lysin in gametes and somatic tissue of male and female M. edulis. The study employs a previously published monoclonal antibody (G26-AG8) to investigate M6 and M7 lysin protein expression, and explores expression of both genes. It is shown that these proteins and their encoding genes are expressed in gametes and somatic tissue of both sexes. This is in contrast to sea urchin bindin and abalone lysin, in which gene expression is strictly limited to males. Although future studies need to clarify the functional importance of both acrosomal proteins in male and female somatic tissue, new insights into the evolution of sperm proteins in marine sessile invertebrates are possible. This is because proteins with male-specific expression (bindin, lysin) might evolve differently than proteins with expression in both sexes (M6/M7 lysin), and the putative function of both proteins in females opens the possibility that the evolution of M6/M7 lysin is under sexual antagonistic selection, for example, mutations beneficial to the acrosomal function that are less beneficial the function in somatic tissue of females.

Combining hydrodynamic modelling with genetics: can passive larval drift shape the genetic structure of Baltic Mytilus populations?

“…; Heß et al . ). Depending on the geographic area hybridization in Mytilus can have contrasting outcomes (stable hybrid zones vs. hybrid swarms; Riginos & Cunningham ).…”

“…In slight contrast, interspecific hybridization may result in novel phenotypes that allow colonization of habitats that are unsuitable for either parent species (Seehausen 2004a;Gross & Rieseberg 2005). In this context, blue mussels of the Mytilus edulis species complex (M. edulis, Mytilus trossulus, Mytilus galloprovincialis) became wellstudied model organisms as they occur as keystone species in coastal ecosystems worldwide and hybridize whenever they come into secondary contact (Koehn 1991;Riginos et al 2006;Springer & Crespi 2007;Bartel et al 2012;Heß et al 2012). Depending on the geographic area hybridization in Mytilus can have contrasting outcomes (stable hybrid zones vs. hybrid swarms; Riginos & Cunningham 2005).…”