RESUMO
The ancient acquisition of the mitochondrion into the ancestor of modern-day eukaryotes is thought to have been pivotal in facilitating the evolution of complex life. Mitochondria retain their own diminutive genome, with mitochondrial genes encoding core subunits involved in oxidative phosphorylation. Traditionally, it was assumed that there was little scope for genetic variation to accumulate and be maintained within the mitochondrial genome. However, in the past decade, mitochondrial genetic variation has been routinely tied to the expression of life-history traits such as fertility, development and longevity. To examine whether these broad-scale effects on life-history trait expression might ultimately find their root in mitochondrially mediated effects on core bioenergetic function, we measured the effects of genetic variation across twelve different mitochondrial haplotypes on respiratory capacity and mitochondrial quantity in the fruit fly, Drosophila melanogaster. We used strains of flies that differed only in their mitochondrial haplotype, and tested each sex separately at two different adult ages. Mitochondrial haplotypes affected both respiratory capacity and mitochondrial quantity. However, these effects were highly context-dependent, with the genetic effects contingent on both the sex and the age of the flies. These sex- and age-specific genetic effects are likely to resonate across the entire organismal life-history, providing insights into how mitochondrial genetic variation may contribute to sex-specific trajectories of life-history evolution.
Assuntos
Envelhecimento/genética , Evolução Biológica , Drosophila/genética , Genes Mitocondriais/genética , Variação Genética , Fosforilação Oxidativa , Animais , Feminino , Masculino , Mitocôndrias/genética , Fatores SexuaisRESUMO
The influence of mitochondrial DNA (mtDNA) mutations on human disease has been extensively studied, but the impact of mutations within the adaptive range is debated. We studied males from lines of Drosophila melanogaster that have a highly standardized nuclear genome but different mtDNA, at two ages. We measured mitochondrial respiration on permeabilized muscle fibers, hydrogen peroxide production of isolated mitochondria and mtDNA copy number of whole individuals. The results show that a small set of naturally occurring mtDNA mutations can have a significant influence on mitochondrial bioenergetics that may change as the organism ages.
Assuntos
DNA Mitocondrial/genética , Drosophila melanogaster/fisiologia , Metabolismo Energético , Mitocôndrias/genética , Mitocôndrias/fisiologia , Mutação , Animais , Respiração Celular , Peróxido de Hidrogênio/metabolismo , Masculino , Fibras Musculares Esqueléticas/metabolismoRESUMO
The aim of this study was to investigate the effects of polycyclic aromatic hydrocarbons (PAHs) on the physiological status of the bivalve Mya arenaria. Specimens were exposed to four different sources of PAHs: aluminium smelter soot, sediment from an industrial discharge pound, charcoal fine particles and dietary PAHs assessed by feeding clams with phytoplankton freshly impregnated with dissolved PAHs. The exposure period lasted 30 days and bivalves were let to recover for an additional 20 days. At days 8, 15, 30 and 50, immune parameters (phagocytic activity and efficiency) were monitored in haemocytes. Oxidative stress measures such as catalase and lipid peroxidation were quantified in digestive gland as well as concentrations of bioaccumulated PAHs. In a second experiment, clams were exposed to [(14)C]-pyrene via the phytoplankton, and the tissue distribution of radiolabelled compound was studied. Glycogen levels in gonad and digestive gland were also measured and gametogenesis stages were investigated. Results showed a high bioaccumulation in clams exposed to dietary PAHs and contaminated sediments. Tissue distribution of [(14)C]-pyrene revealed that the radiolabelled compound persisted mainly in the gonad during 14 days. A decrease of phagocytosis was observed in contaminated male clams. The lipid peroxidation (malondialdehyde) was found to increase in the digestive gland tissues of clams exposed to dietary PAHs, smelter soot and discharge, but no differences were observed in the catalase activity. A delay in gametogenesis occurred in all exposed males and in females contaminated with coke dust and dietary PAHs. Males were more sensitive than females to PAH exposure. A dysfunction in steroid synthesis is suspected to occur due to the exposure to all sources of PAHs.
