Richard W. Siegel

Conditioned courtship inDrosophila and its mediation by association of chemical cues

AlthoughDrosophila melanogaster males usually court virgin females vigorously, a male will perform very little courtship in response to a virgin female if he has previously been in the presence of a fertilized female. The normal courtship response is restored after approximately 3 h [Siegle, R. W., and Hall, J. C. (1979).Proc. Natl. Acad. Sci. USA76:3430–3434]. Experiments designed to account for this phenomenon exclude the possibilities that the visible “rejection” behaviors performed by the fertilized female in response, to the male are either a necessary or a sufficient basis for the transitory decrement in courtship. A role for other visual, cues is also ruled out. However, mutant males with olfactory defects do court virgins after experiences with fertilized females. Also, males exposed to extracts from fertilized females while in the presence of a male or virgin female fly thereafter perform very little courtship with virgin females. Finally, we describe a new mutant strain whose males court and mate with wild-type, virgin females normally; but after such a mating, the wild-type female is readily courted by a wild-type male, and that male subsequently exhibits vigorous courtship of other females. Since both virgin and fertilized females can stimulate males to court them, these observations fuggest the following hypothesis. After fertilization by a wild-type male, a female becomes a source of an aversive chemical cue which is sensed by a courting male [cf. Tompkins, L., and Hall, J. C. (1981).J. Insect Physiol.27:17–21]. The courting male associates that substance with the courtship-stimulating cues emanating from females which he subsequently encounters, and he therefore learns to avoid courting these females.

The role of female movement in the sexual behavior ofDrosophila melanogaster

NormalDrosophila melanogaster males rapidly react to changes in the mobility of mutantshibirets females by performing less courtship when the females are paralyzed and by courting movingshibirets females vigorously. Mutantoptomotor-blind males, which are unable to respond to certain horizontally moving patterns, sustain abnormally short courtship bouts when tested with normal females, almost never perform orientation, one of the courtship behaviors, and require more time to initiate copulation than normal males. These results suggest that males must perceive female movement to perform normal courtship and copulation. Normal females become stationary before copulation occurs. Normal males mate quickly in response to this change in female behavior, while blind males require more time to effect copulation, prolonging the time that the female remains stationary. Mutantsmellblind females, which do not respond to certain odors, continue to move during the time that they are courted by normal or blind males and also require more time to copulate, suggesting that females may stop moving before mating in response to olfactory cues.

Drosophila mutations that alter ionic conduction disrupt acquisition and retention of a conditioned odor avoidance response

We have previously found that genetic alterations in neuronal ion channel function have specific effects on learning and memory of a conditioned courtship behavior in Drosophila. Using a behavioral assay of conditioned odor avoidance, we report here that shaker mutants, in which potassium-channel function is abnormal, are defective in both their rate and maximum level of acquisition when compared to wild-type flies. napts (no action potential, temperature sensitive) mutants, in which nerve excitability is decreased due to faulty sodium-channel function, can achieve a normal (wild-type) level of learning, but the rate of acquisition is reduced. Neither the shaker nor the napts mutations affect memory decay following rest periods greater than 30 min. However, memory may decay more rapidly in both shaker and napts flies during the initial 30-min period following training. These results suggest that neuronal sodium- and potassium-channel function may be of general importance to the processes of acquisition and short-term memory in Drosophila.

Mutational and Pharmacological Alterations of Neuronal Membrane Function Disrupt Conditioning in Drosophila

Neuronal membrane channels of Drosophila melanogaster were altered either genetically or pharmacologically in order to investigate the role of specific ionic currents in the acquisition and retention of a conditioned behavior. Conditioning could not be detected for Shaker mutants, in which the fast transient potassium current (IA) is altered; a second potassium channel mutant, eag (ether a go-go) is conditioned like wild type, but the retention period is abnormally short. The napts mutant (no action potential, temperature sensitive), in which nerve excitability is reduced, also expresses normal acquisition and a shortened period of retention. Double mutants of Sh5 and napts as well as Sh5 treated with tetrodotoxin, are essentially normal with respect to acquisition; in both cases these flies remain retention-defective. These experiments therefore reveal a behavioral phenotype of Drosophila mutants in which the primary physiological defect seems to be in the functioning of specific neuronal ionic channels.

Biological rhythm mutations affect an experience-dependent modification of male courtship behavior inDrosophila melanogaster

SummaryMale courtship behavior in the fruitflyDrosophila melanogaster can be altered by experience and the normal experience-dependent behavioral modification does not occur in flies carrying mutations known to affect conditioned responses (Siegel and Hall 1979; Gailey et al. 1982). The conditioned modification of male courtship is also disrupted by any of 5 independently isolated mutations (perl,perl2,Andante, psi-2 and psi-3) that bring about longer period biological rhythms (Table 1). However, males carrying eitherpers orpero, which have shortened periods and arrhythmic behavior, respectively, are normally conditioned. The failure ofperlmales to respond normally to conditioning cues cannot easily be accounted for by a second mutation outside the clock locus or by multigenic factors. Indeed, the genetic lesion which is responsible for the defective behavioral modification ofperlmutants maps to the chromosomal interval in which theper locus itself resides (Table 3). The aberrant behavior ofperlmutants might be a result of their abnormal daily periodicity, but it cannot be explained by a change in the time of day for optimal conditioning (Table 4). Alternatively, the poor conditioning performance of longperiod clock mutants may indicate that short-cycle endogenous timing mechanisms play an integral role in conditioning behavior.

Mutations specifically blocking differentiation of macroconidia in Neurospora crassa

The asexual life cycle of Neurospora crassa is comprised of three stages, vegetative hyphae, aerial hyphae, and macroconidia. Under appropriate environmental conditions these stages occur in an orderly temporal sequence making possible detailed observations of developmental changes in both living and fixed material. Attention is focused on the origin of conidiophores, from aerial hyphae, and the subsequent differentiation of mature macroconidia. Mutations at four genetically independent loci block the process of conidiation at different developmental points. Analyses of these strains and of double mutant strains constructed by crosses among them indicate the order in which the mutants are phenotypically expressed. Three of the mutations have no evident effects on either vegetative or aerial hyphae and hence appear to be “phase-specific” for macroconidia; tion. New evidence is presented in strong support of the idea that the products of these genes are formed in the aerial hyphae and/or conidiophores.

Higher Behavior in Drosophila Analyzed with Mutations that Disrupt the Structure and Function of the Nervous System

Higher behavior in lower organisms seems an ideal candidate for genetic analysis. At first glance, this is because fixed action patterns such as courtship rituals seem almost certain to be programmed by the action of genes that control the development and function of their nervous systems.

A mutant strain in Drosophila melanogaster that is defective in courtship behavioural cues

Experience-dependent modification of courtship behaviour in Drosophila melanogaster has been previously reported; males that have courted fertilized females thereafter avoid courtship with virgin females for 2–3 h. We report that this modification is dependent upon a behavioural interaction between a courting male and fertilized female. Behavioural comparisons of males of the mutant strain Don Giovanni (dg) and normal males imply that fertilized females release a conditioning cue in response to male courtship. (1) The normal behaviour modifying capacity of fertilized females is dependent upon copulation. Females fertilized by dg do not effectively modify male courtship. (2) dg males are deficient in causing fertilized females to release a conditioning cue; fertilized females which are courted by dg males do not induce modification of behaviour. (3) The behaviour of dg males can be modified if the fertilized females they court have been first courted by normal males. These defects were mapped to the y-cv interval of the X-chromosome.

Developmental regulation of nicotinamide adenine dinucleotide (phosphate) glycohydrolase in Neurospora crassa.

Abstract The formation of nicotinamide adenine dinucleotide (phosphate) glycohydrolase [NAD(P)ase; EC 3.2.2.6] in Neurospora crassa was found to be both spatially and temporally programmed. Ascospores were devoid of the enzyme. Vegetative hyphae contained little or no NADase activity. During the differentiation of aerial cell types (aerial hyphae and macroconidia), the specific activity of the enzyme increased by at least three orders of magnitude. Although transiently associated with young aerial hyphae, the enzyme became an integral and stable part of the mature macroconidia. NAD(P)ase could also be “derepressed” under conditions that permitted aerialogenesis in the absence of conidiation. The increase in the specific activity of NAD(P)ase during cell differentiation required concomitant RNA and protein synthesis; in vitro mixing experiments revealed no cell-specific activators or inhibitors of enzyme activity. The temperature-critical period for the in vitro inactivation of a temperature-sensitive enzyme variant was restricted to the period of actual enzyme expression. The data reported in this paper combined with data reported in a previous paper (Nelson et al., 1975b) underscore an important distinction in studies of development, namely, developmental regulation of a macromolecule versus regulation of development by a macromolecule. This paper provides evidence that NAD(P)ase is developmentally regulated. The previous paper provides evidence that the appearance of this enzyme need not regulate development.