A genetic analysis of the role of neuralized in the notch and EGFR pathways of Drosophila melanogaster

grantor: University of TorontoThe 'neuralized' gene of 'Drosophila melanogaster' is thought to be a member of the neurogenic signalling pathway involved in the development of the embryonic and adult nervous systems. Overexpressing 'neuralized' during development causes dominant phenotypes in the eye, notum and wing of adults. These phenotypes include the production of extra and misplaced bristles in the eye, an increase in the number of notal microchaetae and decrease in macrochaetae, and deletion of portions of wing veins. These dominant phenotypes were used to screen a deficiency kit for modifiers of 'neuralized.' The screen identified deficiencies which uncovered members of both the neurogenic and the EGFR signalling pathways. This interaction was confirmed by directly testing alleles of genes in both pathways for the ability to modify the 'neuralized' overexpression phenotype. It appears that 'neuralized' could play a role in both of these pathways. Biochemical tools to test these interactions have been produced.M.Sc

Temporal Changes in Reproduction, Competition, and Predation after Establishment of Introduced Populations of the greater European Pine Shoot Beetle, Tomicus Piniperda (L.) (Coleoptera: Curculionidae, Scolytinae)

The establishment of exotic species in novel environments is a major environmental concern, however, few long-term studies have examined the effects of these species on their host environment and community, especially in forest ecosystems. The arrival and subsequent spread of the greater European pine shoot beetle, Tomicus piniperda (L.) (Coleoptera: Curculionidae, Scolytinae), into southern Ontario pine forests provided a natural experiment to assess biotic interactions between an exotic species and its new community over several years. Reproductive success of Tomicus piniperda colonies of various ages was studied between 2001 and 2004. The size and composition of competitor and natural enemy complexes present in these communities were also quantified over time. The impact of the natural enemy complexes on T. piniperda reproduction was assessed, Brood production (no. eggs and galleries/female) by T. piniperda populations rapidly approached those reported from its native range in Europe, with lower densities of parental adults. Thus, reproduction remained consistently above the replacement level for this beetle over all four years of study suggesting that these recently-introduced populations were growing rapidly and at a greater rate than in their country of origin. Tomicus piniperda successfully integrated into a large bark beetle community, and appeared to be capable of displacing native beetles to more marginal bark habitats, however, these competitors were not eliminated during the course of the study. The long-term effect of this marginalization on populations of native beetles is uncertain. Tomicus piniperda rapidly acquired natural enemies in the introduced areas, however, natural enemy-caused mortality did not show a regulating effect on its populations. It seems that intraspecific competition, rather than predation, regulates T. piniperda populations following introduction. The implications of these findings for the establishment and spread of exotic species in forest systems are examined, especially with reference to a prominent theory for success, the Enemy Release Hypothesis. In short, the Enemy Release Hypothesis is not applicable to an exotic species that is not regulated by natural enemies in its native range, and assessments of the Enemy Release Hypothesis should always include a determination of enemy regulation of the exotic in its native range.Ph

Neuralized functions cell autonomously to regulate Drosophila sense organ development

Neurogenic genes, including Notch and Delta, are thought to play important roles in regulating cell–cell interactions required for Drosophila sense organ development. To define the requirement of the neurogenic gene neuralized (neu) in this process, two independent neu alleles were used to generate mutant clones. We find that neu is required for determination of cell fates within the proneural cluster and that cells mutant for neu autonomously adopt neural fates when adjacent to wild-type cells. Furthermore, neu is required within the sense organ lineage to determine the fates of daughter cells and accessory cells. To gain insight into the mechanism by which neu functions, we used the GAL4/UAS system to express wild-type and epitope-tagged neu constructs. We show that Neu protein is localized primarily at the plasma membrane. We propose that the function of neu in sense organ development is to affect the ability of cells to receive Notch-Delta signals and thus modulate neurogenic activity that allows for the specification of non-neuronal cell fates in the sense organ