RESUMO
The laboratory has yielded many long-lived mutants of several model-organisms in the past few years. Many of the resulting claims for extended longevity have been nuanced or shown to be restricted to specific conditions, including environments and genetic backgrounds. Here, we test whether the long-lived mutant fruit fly methuselah (mth(1)) displays its apparent superiority in longevity and stress resistance in different environments, at different ages and in correlated traits. The results demonstrate that stress resistance at different times in life is not consistently higher in the mutant relative to its progenitor strain (w(1118)). Furthermore, the mth(1) genotype only leads to an increase in longevity in an environment where reproduction is not stimulated. Also, virgin and mated life span were compared and showed that mating negatively affects life span, especially in the mth(1) individuals. This reduced the life span enhancing effect of the mutation to zero. This apparent environment and mating dependent trade-off between longevity and reproduction supports the disposable soma theory of ageing. We conclude that these data can only provide limited information on natural variation. The data show the need to uncover the full complexity of variation in such traits in natural environments.
Assuntos
Drosophila melanogaster/fisiologia , Longevidade/fisiologia , Experimentação Animal , Animais , Drosophila melanogaster/efeitos dos fármacos , Drosophila melanogaster/genética , Resistência a Medicamentos/fisiologia , Meio Ambiente , Feminino , Fertilidade/fisiologia , Privação de Alimentos/fisiologia , Genótipo , Herbicidas/farmacologia , Masculino , Modelos Animais , Mutação , Paraquat/farmacologia , Reprodução/fisiologia , Fatores Sexuais , TemperaturaRESUMO
In Caenorhabditis elegans, DAF-12 appears to be a decisive checkpoint for many life history traits including longevity. The daf-12 gene encodes a Nuclear Hormone Receptor (NHR) and is member of a superfamily that is abundantly represented throughout the animal kingdom, including humans. It is, however, unclear which of the human receptor representatives are most similar to DAF-12, and what their role is in determining human longevity and disease at old age. Using a sequence similarity search, we identified human NHRs similar to C. elegans DAF-12 and found that, based on sequence similarity, Liver X Receptor A and B are most similar to C. elegans DAF-12, followed by the Pregnane X Receptor, Vitamin D Receptor, Constitutive Andosteron Receptor and the Farnesoid X Receptor. Their biological functions include, amongst others, detoxification and immunomodulation. Both are processes that are involved in protecting the body from harmful environmental influences. Furthermore, the DAF-12 signalling systems seem to be functionally conserved and all six human NHRs have cholesterol derived compounds as their ligands. We conclude that the DAF-12 signalling system seems to be evolutionary conserved and that NHRs in man are critical for body homeostasis and survival. Genomic variations in these NHRs or their target genes are prime candidates for the regulation of human lifespan and disease at old age.
Assuntos
Envelhecimento/fisiologia , Receptores Citoplasmáticos e Nucleares/fisiologia , Receptores de Esteroides/fisiologia , Envelhecimento/genética , Animais , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/fisiologia , Colesterol/metabolismo , Receptor Constitutivo de Androstano , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Evolução Molecular , Regulação da Expressão Gênica , Humanos , Receptores X do Fígado , Longevidade/genética , Receptores Nucleares Órfãos , Receptor de Pregnano X , Receptores de Calcitriol/genética , Receptores de Calcitriol/fisiologia , Receptores Citoplasmáticos e Nucleares/classificação , Receptores Citoplasmáticos e Nucleares/genética , Receptores de Esteroides/genética , Alinhamento de Sequência , Homologia de Sequência , Transdução de Sinais/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologiaRESUMO
There is evidence that longevity and starvation resistance are determined by a common genetic mechanism. Starvation resistance in Drosophila strongly correlates with both fat content and longevity, and is affected by density during rearing. In this study, we examine how three species, Drosophila melanogaster, Drosophila ananassae and Drosophila willistoni, respond to three larval density treatments. Starvation resistance after adult eclosion, and after 2 days of feeding, and longevity were examined in each sex. D. willistoni reacted differently to larval density than the other two species. This species showed an effect of density on longevity whilst D. ananassae and D. melanogaster showed no such effects. The results also indicate that starvation resistance is not solely determined by fat content. Resistance to starvation at two time points after eclosion differed among species. This may reflect differences in resource acquisition and allocation, and we discuss our findings in relation to how selection may operate in the different species.