Albert Kamping

Identification and characterization of the doublesex gene of Nasonia

The doublesex (dsx) gene of the parasitic wasp Nasonia vitripennis is described and characterized. Differential splicing of dsx transcripts has been shown to induce somatic sexual differentiation in Diptera and Lepidoptera, but not yet in other insect orders. Two spliceforms of Nasonia dsx mRNA are differentially expressed in males and females. In addition, in a gynandromorphic line that produces haploids (normally males) with full female phenotypes, these individuals show the female spliceform, providing the first demonstration of a direct association of dsx with somatic sex differentiation in Hymenoptera. Finally, the DNA binding (DM) domain of Nasonia dsx clusters phylogenetically with dsx from other insects, and Nasonia dsx shows microsynteny with dsx of Apis, further supporting identification of the dsx orthologue in Nasonia.

POLYMORPHISM AT THE ADH AND ALPHA-GPDH LOCI IN DROSOPHILA-MELANOGASTER - EFFECTS OF REARING TEMPERATURE ON DEVELOPMENTAL RATE, BODY-WEIGHT, AND SOME BIOCHEMICAL PARAMETERS

The role of developmental time in the world-wide cline of Adh and αGpdh allele frequencies of Drosophila melanogaster, and the relationship with weight and some biochemical characters, were investigated. Experimental strains were constructed with different combinations of Adh and αGpdh alleles but with similar genetic background. Developmental time, adult weight, protein-and triglyceride-content, and ADH and αGPDH enzyme activity were measured at a rearing temperature of 20, 25 and 29°C. Genotype effects were found in all studied characters. In general the developmental times of genotypes were: AdhFF < AdhFS < Adhss and αGpdhFF> αGpdhFS = αGpdhSS. Developmental time and adult weight were strongly affected by rearing temperature. Triglyceride content and ADH and αGPDH enzyme activity were slightly affected by temperature. Interactions between genotype and temperature effects were found for developmental rate, adult weight and protein content. No trade off was observed between developmental time on the one hand and adult weight, protein- and triglyceride-content, and ADH and αGPDH enzyme activity on the other hand. It is argued that developmental rate differences might be one of the underlying mechanisms of the world-wide cline of the Adh and αGPdh allele frequencies.

Latitudinal variation for two enzyme loci and an inversion polymorphism in Drosophila melanogaster from Central and South America

Abstract.— Many organisms show latitudinal variation for various genetically determined traits. Such clines may involve neutral variation and originate from historical events or their maintenance may be explained by selection. For Drosophila melanogaster, latitudinal variation for allozymes, inversions, and quantitative traits has been found on several continents. We sampled D. melanogaster populations in Panama and along a transect of 40 latitudinal degrees on the west coast of South America. Negative correlations with latitude were found for Adhs and αGpdhF allele frequencies and for the frequency of the cosmopolitan inversion In(2L)t in AdhsαpdhF chromosomes. A positive correlation existed between wing length and latitude. Significant correlations were found between these traits and climatic variables like temperature and rainfall. The observed clines show considerable resemblance to those found on other continents. Gametic disequilibrium between Adhs and αGpdhF occurred predominantly at higher latitudes and was caused by the presence of In(2L)t. The reasons for the clinal distributions are discussed and it is argued that selection is the most likely explanation. However, the exact nature of the selective force and the interactions of allozymes with each other and with In(2L)t are complex and not fully understood. In tropical regions In(2L)t‐containing genotypes have higher fitness than ST/ST and Adh and αGpdh hitchhike with the inversion, but there is also evidence for balancing selection at the Adh locus.

Inheritance of gynandromorphism in the parasitic wasp Nasonia vitripennis

The parasitic wasp Nasonia vitripennis has haplo-diploid sex determination. Males develop from unfertilized eggs and are haploid, whereas females develop from fertilized eggs and are diploid. Females and males can be easily distinguished by their morphology. A strain that produces individuals with both male and female features (gynandromorphs) is studied. We provide data on female/male patterning within and between individuals, on environmental effects influencing the occurrence of gynandromorphism, and on its pattern of inheritance. A clear anterior/posterior pattern of feminization is evident in gynandromorphic individuals that developed from unfertilized haploid eggs. The proportion of gynandromorphic individuals can be increased by exposing the mothers to high temperature and also by exposing embryos at early stages of development. Selection for increased gynandromorph frequency was successful. Backcross and introgression experiments showed that a combination of a nuclear and a heritable cytoplasmic component causes gynandromorphism. Analyses of reciprocal F2 and F3 progeny indicate a maternal effect locus (gyn1) that maps to chromosome IV. Coupled with previous studies, our results are consistent with a N. vitripennis sex determination involving a maternal/zygotic balance system and/or maternal imprinting. Genetics and temperature effects suggest a temperature-sensitive mutation of a maternally produced masculinizing product that acts during a critical period in early embryogenesis.

No Patrigenes Required for Femaleness in the Haplodiploid Wasp Nasonia vitripennis

The parasitoid wasp Nasonia vitripennis is an emerging model organism for developmental and behavioral genetics. It reproduces by haplodiploidy; males typically develop parthenogenetically from haploid eggs and females from fertilized diploid eggs. A polyploid mutant strain is available in which females are triploid and lay haploid and diploid eggs that normally develop into males when unfertilized. In contrast to previous reports, ∼2% of triploid females were found to occasionally produce daughters as well as gynandromorphs from diploid unfertilized eggs. Daughter production increased with age and differed among familial lineages. This is the first report of parthenogenetic female development in Nasonia. The results show that a paternally provided genome is not required for femaleness and call for modifications of existing models of sex determination in Nasonia.

The alcohol dehydrogenase polymorphism in populations of Drosophila melanogaster IV. Survival at high temperature

In-vitro alcohol-dehydrogenase assays at 35°C confirmed previous reports that the ADH allozymes in Drosophila melanogaster differed in heat stability in the order SS>FS>FF. Adult mortality at 35°C, however, was not found to be associated with heat stability: mortality of the genotypes decreased in the order null-mutant >SS>FF>FS. Measurements of ADH activity in flies kept for as long as 24 h at 35°C did not show declining ADH activity. It was further found that NAD+ addition to homogenates increased in-vitro heat stability considerably, though the allozymes profited differentially, depending on NAD+ concentration. The relevance of the in vitro measurements to the in vivo situation is discussed in relation to the maintenance of the Adh polymorphism.

INTERACTION BETWEEN THE ADH AND ALPHA-GPDH LOCI IN DROSOPHILA-MELANOGASTER - ADULT SURVIVAL AT HIGH-TEMPERATURE

The role of high temperature resistance in the world-wide cline of Adh and αGpdh allele frequencies of Drosophila melanogaster was investigated. Experimental strains were used with different combinations of Adh and αGpdh alleles but with similar genetic background. The survival time of adult males, reared at different pre-adult temperatures, was measured at 35°C. To investigate the relationship between survival and protein content, triglycerides content and ADH and αGPDH enzyme activity, the latter characters were measured before and after 12 h exposure to 35°C. Three-way anova of survival at 35°C showed significant effects of rearing temperature and Adh genotype, interaction between Adh and αGpdh, interaction between Adh and rearing temperature and interaction between Adh, αGpdh and rearing temperature, αGPDH enzyme activity did not change significantly. Although protein content, triglycerides content and ADH enzyme activity decreased significantly at 35°C, no correlation was observed between survival and these traits. It is concluded that the world-wide cline of Adh and αGpdh allele frequencies cannot simply be explained by the genotypic differences in resistance to high temperature of adult Drosophila melanogaster.

Worldwide latitudinal clines for the alcohol dehydrogenase polymorphism in Drosophila melanogaster: What is the unit of selection?

Geographical clines may reflect the action of natural selection on genetic polymorphisms. In Drosophila melanogaster several latitudinal clines occur for many characters like allozymes, inversions and quantitative traits. The identical nature of these clines on the various continents, both on the Northern and Southern Hemispheres strongly suggests adaptation to specific stress factors. The alcohol dehydrogenase (Adh) polymorphism shows high frequencies of the S allele in tropical regions and declines with latitude. The reasons for this cline are difficult to determine because of the entanglement with other polymorphisms varying with latitude. In this paper the tentative connections with other polymorphisms like alpha-Gpdh, In(2L)t, body size and development time are reviewed with respect to the possible environmental stress factors involved. It is concluded, also from recent experiments, that the (2L)t inversion plays a dominant role in resistance to high temperature and is partly responsible for the Adh cline. Further research is aimed at the specific selective forces acting on Adh, focussing on the physiological and life history aspects.

ADH enzyme activity and Adh gene expression in Drosophila melanogaster lines differentially selected for increased alcohol tolerance

In Drosophila melanogaster, alcohol dehydrogenase (ADH) activity is essential for ethanol tolerance, but its role may not be restricted to alcohol metabolism alone. Here we describe ADH activity and Adh expression level upon selection for increased alcohol tolerance in different life‐stages of D. melanogaster lines with two distinct Adh genotypes: AdhFF and AdhSS. We demonstrate a positive within genotype response for increased alcohol tolerance. Life‐stage dependent selection was observed in larvae only. A slight constitutive increase in adult ADH activity for all selection regimes and genotypes was observed, that was not paralleled by Adh expression. Larval Adh expression showed a constitutive increase, that was not reflected in ADH activity. Upon exposure to environmental ethanol, sex, selection regime life stage and genotype appear to have differential effects. Increased ADH activity accompanies increased ethanol tolerance in D. melanogaster but this increase is not paralleled by expression of the Adh gene.

Starvation resistance in Drosophila melanogaster in relation to the polymorphisms at the Adh and αGpdh loci

Abstract In view of the world-wide latitudinal cline of the Adh and α Gpdh allozyme frequencies of Drosophila melanogaster and the interactions between these loci, experiments were performed to study the phenotypic effects of these loci. Starvation resistance, oxygen consumption, body weight, protein content and triglycerides content were measured in flies with all possible combinations of Adh and α Gpdh alleles. Genotypic differences were found for survival time under food deprivation, body weight, protein content and triglycerides content. Oxygen consumption did not differ significantly between genotypes. A significant positive correlation was observed between triglycerides content and starvation resistance. Body weight, protein content and triglycerides content decreased significantly during starvation but no rate differences between genotypes could be found. It is argued that genotypic differences in starvation resistance and triglycerides content can play a role in the maintenance of the world-wide cline of Adh and α Gpdh allele frequencies.