ProjectStructural & functional characterisation of novel mitochondrial gene products in freshwater mussels (Bivalvia: Unionoida)
Unlike all other animals, who pass mitochondrial DNA (mtDNA) strictly from mother to offspring, many species of bivalves have a unique inheritance method called "doubly uniparental inheritance." These species are characterized by the presence of two distinct mtDNA lineages: M mtDNA passed on by males and found in spermatozoides (Dalziel & Stewart, 2002), and F mtDNA passed on by females, found in all tissues of females, and somatic tissues of males (Garrido-Ramos, Stewart et al 1998). Recently, Breton et al. (2011) discovered that mtDNA in mussles contains two extra genes – one in the F mtDNA, the other in the M mtDNA. These genes synthesize proteins whose function is not yet known, but is not related to energy production like the other 13 mitochondrial genes. Interestingly, some mussels are also hermaphrodites: they act as both sexes, but have lost M mtDNA and have F mtDNA in which the extra gene is strongly silenced, and possibly non-functioning. This suggests that mussels are potentially the only members of the animal kingdom to have a sex-determining system that directly involves mitochondria. My master's project will be the first to characterize the molecular evolution, structure, and function of these new genes and their products. The first step is amplifying and sequencing these genes from eight species with separate sexes and five hermaphroditic species. The sequences will be translated into amino acids, and a suite of bioinformatic programs will be used to predict the structure and function of the proteins. P-distances of nucleotide and amino acid sequences will be used to compare rates of evolution and synonymous versus non-synonymous mutations. Finally, a search for premature stop codons and 3' RACE will be used to asses whether the new gene is functional in hermaphrodites.