Interactions between cytoplasmic and nuclear genomes confer sex-specific effects on lifespan inDrosophila melanogaster

Abstract

Acknowledgements:We are grateful to members of the Dowling and Sgró labs for their support in the lab work associated with this project, and four anonymous reviewers for comments on a previous version of the manuscript. ABSTRACT 1 A large body of studies has demonstrated that genetic variation that resides outside of the cell 2 nucleus can affect the organismal phenotype. The cytoplasm is home to the mitochondrial 3 genome and, at least in arthropods, often hosts intracellular endosymbiotic bacteria such as 4 Wolbachia. While numerous studies have implicated epistatic interactions between 5 cytoplasmic and nuclear genetic variation as key to mediating patterns of phenotypic 6 expression, two outstanding questions remain. Firstly, the relative contribution of 7 mitochondrial genetic variation to other cytoplasmic sources of variation in shaping the 8 phenotypic outcomes of cyto-nuclear interactions remains unknown. Secondly, it remains 9unclear whether the outcomes of cyto-nuclear interactions will manifest differently across the 10 two sexes, as might be predicted given that cytoplasmic genomes are screened by natural 11 selection only through females as a consequence of their maternal inheritance. Here, we address 12 these questions, creating a fully-crossed set of replicated cyto-nuclear populations derived from 13 three geographically distinct populations of Drosophila melanogaster, and measuring the 14 lifespan of males and females from each population. We report cyto-nuclear interactions for 15 lifespan, with the outcomes of these interactions differing across the sexes, and reconcile these 16 findings with information on the full mitochondrial sequences and Wolbachia infection status

Genetic sex determination and sex-specific lifespan in tetrapods – evidence of a toxic Y effect

“…This is not the case in males of species with ZW sex-determination systems because in these species females are the heterogametic sex, and hence copies of both sex chromosomes are inherited maternally along with the cytoplasm. Indeed, recent evidence shows that cyto-nuclear interactions have sex-specific lifespan effects in D. melanogaster [27], which opens yet another exciting line of research for future studies. Although it is tempting to interpret our negative finding of a toxic W effect in line with the predictions above, this finding must be taken with caution for two methodological reasons: our sample size for birds was approximately half than that for mammals, and autosome size (on which many of our relative measures are based) is more difficult to estimate in birds than in mammals due to bird karyotypes often including a large number of micro-chromosomes that increased measurement error in our estimations of bird chromosome sizes.…”