Sex Differences in the Effect of Dietary Restriction on Life Span and Mortality Rates in Female and Male Drosophila Melanogaster
Department of Biology, University College London, Darwin Building, Gower Street, London WC1E 6BT, United Kingdom.The Journals of Gerontology Series A Biological Sciences and Medical Sciences (Impact Factor: 5.42). 02/2004; 59(1):3-9. DOI: 10.1093/gerona/59.1.B3
Dietary restriction (DR) has been shown to increase life span in taxonomically diverse animal species. In this study we tested for sex differences in the response of life span to graded severity of DR in Drosophila melanogaster. In both sexes, life span peaked at an intermediate food concentration and declined on either side. However, the magnitude of the response and the food concentration that minimized adult mortality differed significantly between the sexes. Female life span peaked at a food concentration 60% of the standard laboratory diet compared to a concentration of 40% for males. Moreover, female flies subject to DR lived up to 60% longer than did starved or fully fed females, whereas males subjected to DR lived only up to 30% longer. Analysis of age-specific mortality rates showed that DR extended life span by decreasing baseline mortality rates in both sexes, and to a greater extent in females. The differences in the response to DR in female and male Drosophila may be due to previously documented sex differences in sensitivity of life span to insulin/insulin-like growth factor-1 signalling or in nutrient/energy demand and allocation/utilization.
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- "Reproductive activity generally decreases survival in both sexes (e.g. courtship behaviour in males, egg production and the related high nutritional intake and metabolism in females: Soliman & Van Herrewege, 1988; Cordts & Partridge, 1996; Magwere et al., 2004). However, reproduction is rarely taken into account in previous studies of hsp functions. "
ABSTRACT: Ageing and the resulting increased likelihood mortality are the inescapable fate of organisms because selection pressures on genes that exert their function late in life is weak, promoting the evolution of genes that enhance early-life reproductive performance at the same time as sacrificing late survival. Heat shock proteins (HSP) are known to buffer various environmental stresses and are also involved in protein homeostasis and longevity. The characteristics of genes for HSPs (hsp) imply that they affect various life-history traits, which in turn affect longevity; however, little is known about the effects of hsp genes on life-history traits and their interaction with longevity. In the present study, the effects of hsp genes on multiple fitness traits, such as locomotor activity, total fecundity, early fecundity and survival time, are investigated in Drosophila melanogaster Meigen using RNA interference (RNAi). In egg-laying females, RNAi knockdown of six hsp genes (hsp22, hsp23, hsp67Ba, hsp67Bb, hsp67Bc and hsp27-like) does not shorten survival but rather increases it. Knockdown of five of those genes on an individual basis reduces early-life reproduction, suggesting that several hsp genes mediate the trade-off between early reproduction and late survival. The data indicate a positive effect of hsp genes on early reproduction and also negative effects on survival time, supporting the antagonistic pleiotropic effects predicted by the optimality theory of ageing.
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- "Although individuals of both sexes should respond to nutrient limitation in ways that maximize their lifetime fitness (Collins 1980), males and females have distinct nutritional requirements based on their divergent reproductive roles. To date, only a few studies have examined sex-specific responses to early food limitation (but see Karlsson et al. 1997; Clarebrough et al. 2000; Hunt et al. 2004; Gwynne 2004; Boggs and Freeman 2005; Magwere et al. 2004; Maklakov et al. 2008; Stillwell and Davidowitz 2010). Such sex-specific responses may be especially marked in organisms whose mating systems include nuptial gifts. "
ABSTRACT: Animals with complex life cycles respond to early food limitation by altering the way resources are allocated in the adult stage. Response to food limitation should differ between males and females, especially in organisms whose mating systems include nutritional nuptial gifts. In these organisms, males are predicted to keep their allocation to reproduction (sperm and nuptial gift production) constant, while females are predicted to sacrifice allocation to reproduction (egg production) since they can compensate by acquiring nuptial gifts when mating. In this study, we investigated how dietary nitrogen limitation during the larval stage affects sex-specific resource allocation in Pieris rapae butterflies. Also, we tested whether nutrient-limited females increased nuptial gift acqui-sition as a way to compensate for low allocation to reproduction. We found that as predicted females, but not males, sacrifice allocation to reproduction when larval dietary nitrogen is limited. However, females were unable to compensate for this low reproductive allocation by increasing their mating rate to acquire additional gifts. Females reared on low nitrogen diets also reduced wing coloration, a potential signal of female fecundity status. We suggest that female mating frequency is constrained by male mate choice based on females' wing coloration. This study provides new insights into how larval dietary nitro-gen, a key nutritional resource for all herbivores, alters male and female allocation to reproduction as well as to ornamentation.
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- "The life span of male Drosophila was measured at 25oC. Females were excluded from the life span analysis due to observed sex differences regarding the effect of dietary restriction on lifespan . Adult flies were collected 24-hours post eclosion and maintained in standard culture vials (25 mm x 95 mm) with a maximum of 10 flies per vial. "
ABSTRACT: Axonal transport, a form of long-distance, bi-directional intracellular transport that occurs between the cell body and synaptic terminal, is critical in maintaining the function and viability of neurons. We have identified a requirement for the stathmin (stai) gene in the maintenance of axonal microtubules and regulation of axonal transport in Drosophila. The stai gene encodes a cytosolic phosphoprotein that regulates microtubule dynamics by partitioning tubulin dimers between pools of soluble tubulin and polymerized microtubules, and by directly binding to microtubules and promoting depolymerization. Analysis of stai function in Drosophila, which has a single stai gene, circumvents potential complications with studies performed in vertebrate systems in which mutant phenotypes may be compensated by genetic redundancy of other members of the stai gene family. This has allowed us to identify an essential function for stai in the maintenance of the integrity of axonal microtubules. In addition to the severe disruption in the abundance and architecture of microtubules in the axons of stai mutant Drosophila, we also observe additional neurological phenotypes associated with loss of stai function including a posterior paralysis and tail-flip phenotype in third instar larvae, aberrant accumulation of transported membranous organelles in stai deficient axons, a progressive bang-sensitive response to mechanical stimulation reminiscent of the class of Drosophila mutants used to model human epileptic seizures, and a reduced adult lifespan. Reductions in the levels of Kinesin-1, the primary anterograde motor in axonal transport, enhance these phenotypes. Collectively, our results indicate that stai has an important role in neuronal function, likely through the maintenance of microtubule integrity in the axons of nerves of the peripheral nervous system necessary to support and sustain long-distance axonal transport.
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