Mitochondria-targeted plastoquinone derivative SkQ1 increases early reproduction of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> at the cost of early survival

It was previously found that 20 pM SkQ1 (10-(6′-plastoquinonyl) decyltriphenylphosphonium) solution increased lifespan of virgin females and males of the fruit fly Drosophila melanogaster with maximal and highly reproducible effect on early survival of females. In this paper we demonstrate that SkQ1 solution of the same concentration does not increase lifespan of mated females and males, early effect on female survival being absent, whereas early fertility and the total number of progeny are elevated in treated flies. Increase in fertility observed in young mated females instead of increase of survival typical for young virgin females might illustrate the trade-off between the fly’s lifespan and reproduction.     

Genotype-environment interaction for quantitative trait loci affecting life span in Drosophila melanogaster

The nature of genetic variation for Drosophila longevity in a population of recombinant inbred lines was investigated by estimating quantitative genetic parameters and mapping quantitative trait loci (QTL) for adult life span in five environments: standard culture conditions, high and low temperature, and heat-shock and starvation stress. There was highly significant genetic variation for life span within each sex and environment. In the analysis of variance of life span pooled over sexes and environments, however, the significant genetic variation appeared in the genotype x sex and genotype x environment interaction terms. The genetic correlation of longevity across the sexes and environments was not significantly different from zero in these lines. We estimated map positions and effects of QTL affecting life span by linkage to highly polymorphic roo transposable element markers, using a multiple-trait composite interval mapping procedure. A minimum of 17 QTL were detected; all were sex and/or environment-specific. Ten of the QTL had sexually antagonistic or antagonistic pleiotropic effects in different environments. These data provide support for the pleiotropy theory of senescence and the hypothesis that variation for longevity might be maintained by opposing selection pressures in males and females and variable environments. Further work is necessary to assess the generality of these results, using different strains, to determine heterozygous effects and to map the life span QTL to the level of genetic loci.     

Transpositions of mobile dispersed genes in Drosophila melanogaster and fitness of stocks

Summary In situ hybridization with polytene chromosomes was used to demonstrate the transposition of mobile dispersed genes (mdg)-1 and 3 following the selection of flies from low reproductive activity and vability (LA stock) for high reproductive activity, viability and fitness (LA⁺ and HA stocks).The inbred LA stock is continuously selected for low reproductive activity and viability and maintains at least for twentyfive generations a characteristic pattern of mdg-1 distribution in 14–15 sites. Inbred LA⁺ and HA stocks exhibit a changed pattern of mdg-1 locations and the number of sites reaches 21–25. Parallel and independent selection for higher viability may lead to similar characteristic changes in the localization of mdg-1.In several independent experiments we observed, within one generation, a spontaneous and saltatory growth of viability and fitness in the mass-bred LA stock. In these cases new mdg-1 and mdg-3 sites reproducibly appeared to within several bands, some of them characteristic of LA⁺ and HA stocks.We discuss the possible role of mdg in determining the quantitative characters of individuals and their fitness.     

Outcross-dependent transpositions of copia-like mobile genetic elements in chromosomes of an inbred Drosophila melanogaster stock

Summary Transpositions of copia-like mobile genetic elements (MDG1, MDG3 and copia) were studied in crosses of the inbred maladaptive LA line with other laboratory lines made in order to replace specific chromosome pairs in the LA line. Individuals with various hybrid genotypes displayed changed chromosomal patterns of mobile elements compared with the parent LA chromosomes. Variability of the chromosomal molecular structure in hybrids was observed when crossing over was suppressed in the process of hybrid genome constructions. Multiple transposition events were detected in hybrid genomes carrying the second chromosomal pair of the LA line, but not if it was replaced by the second chromosome of the Swedish-b stock. No transpositions were detected in control crosses that did not involve the LA line. Outcross-dependent MDG1 transposition hot spots in the LA second chromosome were found to coincide with previously established hot spots for spontaneous transpositions in the LA line coupled with a fitness increase. The data obtained demonstrate that crosses involving inversions suppressing crossing over cannot guarantee that the chromosomal molecular content will remain the same: it can change as a result of mobile element trans-positions.     

Age Dependence of the Level ofcopia Retrotransposon Expression in the Testes of Drosophila melanogaster

Expression of the lacZ reporter gene controlled by various deletion derivatives of the regulatory region of the copia retrotransposon was studied in the testes of adult transgenic males of the Drosophila melanogaster y ¹ w ^67c23(2) strain at the age of 3, 6–9, 12–15, 18–21, and 24–27 days. When the construct contained the full-length regulatory region, which included the 5-long terminal repeat (LTR) and the 5-untranslated region (UTR), expression was the lowest in males aged 12–15 days and the highest in males aged 3 or 24–27 days. A similar V-shaped age dependence was previously observed for the copia transposition rate and RNA content in a strain with a high rate of copia transposition. Thus, the V-shaped age dependence of expression, which is unusual for Drosophila, proved to be characteristic of copiaregardless of its transposition rate. Deletion of the 5 or 3 end of the LTR, but not of the UTR, changed the age dependence of the level of reporter gene expression. In this case, expression was the highest in 3-day-old males and gradually decreased with age, as typical for many Drosophila genes. It was assumed that the 5- and 3-terminal regions of the copiaLTR contain regulatory elements responsible for the V-shaped age dependence of expression, while the expression level depends to a greater extent on the regulatory elements of UTR.