Jean-Marc Jallon

The chemical basis for sex recognition in Drosophila melanogaster

Chemical cues were recognized to play a predominant role in initiating male courtship behaviour in Drosophila melanogaster as measured by the number and duration of wing-vibration responses elicited in test males. The effect was associated with compounds specific to the female cuticle, for which we describe a simple extraction procedure. Female active extracts were compared with behaviourally non-active extracts from males, using gas-liquid and thin-layer chromatography. Using these preparative methods, long-chain hydrocarbons were isolated and activity was found only among unsaturated molecules. One, heptacosadiene, inducing the highest level of courtship, appears to be the main aphrodisiac pheromone of the female D. melanogaster. This compound is specific to females of the species and is the most abundant of their cuticular hydrocarbons.

Pheromones, mate recognition and courtship stimulation in the Drosophila melanogaster species sub-group

Abstract Female fruitflies of certain species of Drosophila possess cuticular hydrocarbons which act as contact pheromones, capable of inducing male courtship. In three species of the D. melanogaster species subgroup ( D. melanogaster, D. sechellia and D. erecta ) adult males and females have hydrocarbons of different lengths and structures. In four other species ( D. simulans, D. mauritiana, D. yakuba and D. teissieri ) there is no qualitative difference between the sexes. Observations of courtships showed that hydrocarbons act as courtship-inducing pheromones in all the species studied here. Males can be induced to court other flies, regardless of sex or species, if the hydrocarbons of the courted fly correspond to the main female cuticular hydrocarbon of the species of the courting male. Males from species that do not show a hydrocarbon dimorphism responded mainly to the principal hydrocarbon of their species. Males from the dimorphic species tended to respond to a wider range of hydrocarbons, and also showed high levels of courtship with young flies of both sexes and all species, whose hydrocarbons had some structural similarities to those of homotypic adult females.

VARIATIONS IN CUTICULAR HYDROCARBONS AMONG THE EIGHT SPECIES OF THE DROSOPHILA MELANOGASTER SUBGROUP

In addition to protecting against desiccation, some of the hydrocarbons of the waxy cuticle have previously been shown to be mating pheromones in Drosophila melanogaster and D. simulans. Therefore, cuticular hydrocarbons were compared among the eight species in the D. melanogaster subgroup. For the two cosmopolitan species and several geographic strains that were studied, all males are quite similar with very abundant monoenes. The major compound in most cases is 7‐tricosene. Only three exceptions were found: D. sechellia, and the Afrotropical strains of D. melanogaster and D. simulans.

Courtship inDrosophila sechellia: Its structure, functional aspects, and relationship to those of other members of theDrosophila melanogaster species subgroup

The courtship behavior of Drosophila sechelliais described. Male wing displays are mainly vibration and scissoring, with low levels of rowing. As courtship proceeds the proportion of courtship spent in male wing vibration and licking increases, whereas female movement decreases. The male courtship song of sechelliacontains pulse song but no sine song. This species also shows a distinctive “copulation song” associated with mounting and copulation. The main cuticular hydrocarbon in females is 7,11-heptacosadiene. The number of copulations increased when flies were placed in the presence of food. Visual and acoustic stimuli appear to be important for mating. A multidimensional comparison was used to compare members of the melanogaster species subgroup, based upon courtship behavior, song characteristics, and cuticular hydrocarbons. A multidimensional comparison of courtship sequences in sechellia, melanogaster, simulans,and mauritianashowed differences in variability between the two island species as compared to the two cosmopolitan species. The courtship song of D. orenais described: it shows both sine and pulse song; there is also a “copulation song” in this species.

A NEW ACOUSTIC SIGNAL OF THE FRUIT-FLIES DROSOPHILA SIMULANS AND D. MELANOGASTER

ABSTRACT We found a new acoustic signal in Drosophila simulans (si) and D. melanogaster (me). It is a ‘rejection signal’ (RS) produced by adult males and young males and females in response to the courting behaviour of mature males who emit ‘pulse songs’ (i.e. love song: LS). It occurs most frequently in si, less in adults me except if the interacting males belong to different chemical morphs (i.e. temperate or equatorial population). There are no differences in the LS characteristics directed to various sexes and ages. The RSs produced by adult males or by young animals do not differ significantly either. They are emitted by neither virgin nor fecundated adult me females but a few times by virgin adult si females. The RS (like the LS) is a multipulse signal but intervals between pulses are about twice those of LS, around 90 ms for si and 80 ms for me. They are very irregular, as is the distribution of energy along the bandwidth mainly between 300 and 800 Hz for si and 200 and 600 Hz for me. The sound lev...

Evidence for two nicotinamide binding sites on L-glutamate dehydrogenase

Abstract Circular dichroism saturation in the nicotinamide band of NADH, provides direct evidence for the binding of two nicotinamide rings per protomer of L-glutamate dehydrogenase. These two binding sites are titrated by NADH in the presence of both the substrate (L-glutamate) and an allosteric effector (GTP or Zn2+) while only one reacts in the absence of the effector. We suggest that the second binding site, not accessible to NADPH, is demasked by a conformational change of the protein induced by the allosteric effector.

Genetic and Developmental Factors in the Olfactory Response of Drosophila melanogaster Larvae to Alcohols

Olfactory responses of Drosophila melanogaster larvae to a homologous series of primary alcohols (methanol ... decanol) were tested. Alcohols at either extreme of the chain lengths studied (methanol, ethanol and decanol) evoked no significant responses. Heptanol and nonanol both produced doseindependent responses, larvae being attracted to heptanol and repulsed by nonanol. The remaining alcohols elicited dose-related attractive responses. Responses to hexanol and nonanol decline with increasing larval age. Genetic differences were found for the response to heptanol, with larvae from a Japanese strain. Katsunuma, being indifferent to this substance. Chromosome exchange revealed that a major factor involved in the response to heptanol is located on chromosome II; factors on chromosome III quantitatively modulate this response. Three mutant strains were isolated following EMS mutagenesis of chromosome III. These three strains, IndifferentA, IndifferentB and IndifferentC, show incomplete or total anosmia when stimulated with nonanol. Adult flies from these strains show similar effects. IndifferentB and C strains are dominant over the Canton-S control strain: the IndifferentA strain shows semi-dominance. Results are discussed in the light of the ecology of Drosophila larvae and the relation between olfactory stimulus and receptor conformation and number.

Mechanism of bovine liver glutamate dehydrogenase self-association: I. Kinetic evidence for a random association of polymer chains

We have undertaken a study of the mechanism of bovine liver glutamate dehydrogenase self-association with scattered light temperature-jump and stopped-flow relaxation techniques. Our results indicate a “random association” mechanism in which association-dissociation reactions occur between all polymerized forms of the oligomer according to where the specific rate-constants ka and kd are independent of chain length. At 15 °C we find ka = 1.5 × 106 m−1s−1 and kd = 5 s−1. Standard thermodynamic functions and activation parameters have been determined from equilibrium and kinetic experiments at different temperatures. Large entropy effects and heat capacities indicate water participation in the self-aggregation process. We suggest that the rate-determining step in the association of glutamate dehydrogenase molecules is the “melting” of a layer of ordered water structure between two hydrophobic contact sites.

Complex Chemical Messages in Drosophila

Most animals use several types of sensory signals to communicate with homospecific and heterospecific individuals. The class of chemical messages known as pheromones was first established on the basis of a series of insect studies (Karlson and Butenandt, 1959). Pheromones were initially taken to be airborne substances; however, contact pheromones and pheromones transmitted in water have since been shown to exist throughout the animal kingdom. Pheromones may play various roles: for example, sexual attractants, or alarm or aggregation signals; further, they may be excitatory or inhibitory (Bell and Carde, 1984).

Role of the ejaculatory bulb in biosynthesis of the male pheromone cis-vaccenyl acetate in Drosophila melanogaster.

In Drosophila melanogaster, the male ejaculatory bulb is the site of synthesis of a male-specific pheromone, cis-vaccenyl acetate, which functions as both an attractant and an anti-aphrodisiac. This long monounsaturated acetate is structurally similar to a number of shorter gland-synthesized moth pheromones. The cell monolayer that forms the Drosophila male ejaculatory bulb wall is responsible for the production and secretion of cis-vaccenyl acetate into the seminal fluid. When dissected bulbs were incubated with sodium [14-C]-acetate (or deuterated acetate), a labeled acetate ester was synthesized. The labeled acetate ester co-migrated with cis-vaccenyl acetate in thin layer chromatography. Incubation of the abdomens of males from which the ejaculatory bulbs had been removed, or the abdomens of females, with radiolabeled acetate did not yield any acetate ester, but did yield other lipid products, including hydrocarbons. When the isolated labeled acetate ester was hydrolyzed, no radioactive vaccenol was formed. This strongly suggests that the acetyl group is incorporated via a transacetylation reaction, but that the vaccenyl moiety is not synthetized in the blub. The transacetylation enzyme activity was localized in the microsomal subfraction of the bulb homogenate, and its affinity for vaccenol was not very different from that reported for monounsaturated alcohol substrates in moths.