The effects of gene-environment interaction on the expression of longevity

Abstract

Several previous attempts at selecting for increased life span with Drosophila have failed to obtain a response to selection, and postulate that life span is controlled by non-genetic maternal effects instead of genes. In other experiments, however, populations have responded. This study uses a set of true-breeding long-and short-lived stocks developed by in Vitro selection to examine the effect on life span of developmental environment and outcrossing.The expression of genes for life span is shown here to vary as a result of a gene-environment interaction and is strongly affected by the environment during development. The longevity of F1 crosses between long-and short-lived parental lines is additive when the density of larvae is high and unfixed, showing that life span is controlled by genes and not nongenetic maternal effects. But, when numbers of larvae are held low and constant, as in studies where selection fails, life span of crosses and parental lines is greatly restricted. The failure of some previous attempts at selection, therefore, appears to have resulted from the introduction, through experimental design, of strong artifactual environmental effects that Limit the phenotypic expression of genes for life span and the effectiveness of selection.Comparison of fecundity in parental and F1 lines shows that selection for increased life span antagonistically reduces early-life fecundity. Short-lived, parental lines, reproduced at an early age in life, lay 22-24 per cent more eggs in the same period than do long-lived lines selected for reproduction at a late age.

Selection for life span in Drosophila melanogaster

“…This study, and that of Clare and Luckinbill (1985) show that selection for reproduction late in life can increase longevity, as theory predicts, and also that powerful gene-environment interactions influence adult life span and consequently, the effectiveness of selection. The inability of preceding studies to obtain sensible results during selection appears to have resulted from the artifactual introduction of these gene-environment interactions by controlling the density of developing populations to low levels.…”

“…That is, the same genotype should manifest highly different phenotypes when raised at different developmental densities. Clare and Luckinbill (1985) have tested these predictions using the strains of this study. Their results show that in the stressful, uncontrolleddensity environment, the phenotype of F1 individuals is additively distributed, and intermediate between long-and short-lived parental lines.…”

Larval regulation of adult longevity in a genetically-selected long-lived strain of Drosophila

“…However, Curtsinger (1990) has shown that environmental effects are also very important in regulating the life span of Drosophila. Indeed, Clare and Luckinbill (1985) have previously reported the existence of a gene-environment interaction for the L strain, a phenomenon which was later confirmed by us (Wells et al, 1987). The mechanism of this gene-environment interaction is to date unknown.…”

“…Our selected strains, which were originally derived from wild-caught flies, also exhibit an obvious larval density-dependent longevity (Clare & Luckinbill, 1985;Wells etal., 1987).…”

Inherited stress resistance and longevity: a stress theory of ageing

“…In the former experiments the stress level was higher than in the latter, because competition between larvae occurred. Based upon data of Clare & Luckinbill (1985), some stress from competition appears necessary to obtain a response to selection (Parsons, 1987), and hence the negative correlations expected under antagonistic pleiotropy.…”