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In order to recover new mutant alleles of the Polycomb group gene Additional sex combs (Asx), mutagenized chromosomes were screened over the putative Asx allele XT129. Thirteen new mutant strains that fail to complement XT129 were recovered. Unexpectedly, the thirteen strains sorted into four complementation groups. Recombination mapping suggests that each complementation group represents a separate locus. The largest group fails to complement a deletion of Asx and maps in the vicinity of 2-72, the published location of Asx. All new mutant strains enhance the phenotype of Polycomb mutant flies and are not allelic to any previously discovered second chromosome Polycomb group genes. Therefore, the new mutants may be considered putative new members of the Polycomb group. This study suggests that Asx belongs to a sub-group of genes displaying intergenic non-complementation. / Science, Faculty of / Zoology, Department of / Graduate

Protein phosphorylation is now recognized to be one of the most important means of regulating protein activity. An approach was taken that was aimed at identifying new protein Serine/Threonine kinase genes in the fruit fly Drosophila melanogaster. Three of the kinases identified were chosen for molecular characterization: a Map kinase-activated protein kinase-2 homolog (DmMAPKAPK-2); a novel female germline specific kinase ( loki); and the homolog of the vertebrate cdk7 genes (Dmcdk7). Among those, Dmcdk7 was chosen for in depth molecular and genetic characterization. Cdk7 has previously been shown in vertebrate systems to phosphorylate and activate many different Cyclin-dependent kinases (Cdks) in vitro. However, conclusive evidence that Cdk7 could act as a Cdk-activating kinase (CAK) in vivo had remained elusive, and became even controversial. Adding to the controversy was the fact that in the budding yeast S. cerevisiae, CAK activity is provided by the CAK1/Civ1 protein which is unrelated to Cdk7. It was therefore proposed that the CAK activity of Cdk7 may be an in vitro artefact. In an attempt to resolve this issue null and temperature sensitive mutations of the Dmcdk7 gene have been created. The results obtained using these mutant alleles of Dmcdk7 demonstrate that cdk7 is necessary for CAK activity in vivo in a multicellular organism. It is shown that cdk7 activity is required for the activation of both Cdc2/Cyclin A and Cdc2/Cyclin B complexes, and for cell division. In addition to validate the function of Cdk7 as a bona fide regulator of the cell cycle, these results suggest that there may be a fundamental difference in the way metazoans and budding yeast effect a key modification of Cdks. Phosphorylation events at different sites (including the T-loop) are also known to be involved in stabilizing the Cdk7/Cyclin H dimer in vitro, and have been shown to occur in vivo. Surprisingly, the in vivo analysis of different phosphorylation mutant forms of DmCdk7 f

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"May 2003" / Bibliography: leaves 72-87. / iii, 87 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2003

Courtship and copulation behaviors in Drosophila melanogaster males are regulated by sex-specific products from the gene fruitless (fru). Male-specific FRU proteins (FRU[superscript M]) are putative transcription factors of the BTB-ZnF family that likely act by controlling development and maintenance of the neural circuitry used during male sexual behavior. However, which neuronal characteristics are regulated by FRU[superscript M] is mostly unknown and how FRU[superscript M] neurons are grouped into circuits and the role that specific neuronal circuits play in sexual behavior has not been elucidated. I have identified a subset of FRU[superscript M] neurons that co-express the transcription factor, Engrailed (En). After fru[superscript M]-RNAi-induced targeted removal of FRU[superscript M] proteins from FRU[superscript M]/En neurons, males were impaired in their ability to initiate or maintain copulation. Further, I examined two characteristics, the initial projections and neurotransmitters used by FRU[superscript M]/En neurons. Males and females showed a difference in the neurochemistry of FRU[superscript M]/En neurons in the thoracic ganglia; this neurochemistry is disrupted in fru mutant males. For one cohort of serotonergic neurons in the abdominal ganglion that were previously shown to be dependent on FRU[superscript M] for expression of serotonin, I determined that FRU[superscript M] works in conjunction with other sex-specific genes, TAKEOUT (TO) and DOUBLESEX (DSX), to induce of serotonin expression in males; in females serotonin expression is repressed by DSX and TO. Finally, I performed a genetic screen for genes that interact with, or are downstream targets of, fru, dsx, or dissatisfaction (dsf). I assessed fertility, copulation success, and abdominal muscle development of EMS-mutagenized flies, resulting in one fly line in which homozygous mutant animals had a novel muscle phenotype. By genetic tests, the mutation was found to be allelic to string, which encodes a Cdc25- like phosphatase. Taken together, my research demonstrates that subsets of FRU[superscript M] neurons function in circumscribed circuits to regulate specific portions of sexual behavior, and that FRU[superscript M], along with other sex-specific genes, controls development of these neurons in part by determining neurochemistry. Further, FRU[superscript M] likely directs multiple downstream targets, in different subsets of neurons in which it is expressed, which collectively provide correct development of neural circuits underlying courtship and copulation behavior. / Graduation date: 2006

The fruitless (fru) gene in Drosophila melanogaster is a multifunctional gene having sex-specific functions in the regulation of male sexual behavior and sex-nonspecific functions affecting adult viability and external morphology. While much attention has focused on fru's sex-specific roles, little is known about its sex-nonspecific functions. The embryonic central nervous system (CNS) is a prime model system in which to study the genetic control of axonal outgrowth and proper CNS formation. I have examined fru's sex-nonspecific role in embryonic neural development. fru transcripts and FRU proteins from sex-nonspecific promoters are expressed beginning at the earliest stages of neurogenesis and subsequently in both neurons and glia. In embryos that lack most or all fru function, Fasciclin II- and BP102-positive axons appeared to defasciculate from their normal pathway and fasciculate along aberrant neuronal pathways, suggesting that one of fru's sex-nonspecific roles is to regulate axonal differentiation. I next examined whether the loss of fru function in FRU-expressing neuronal precursors causes neuronal fate change. Analysis of fru mutant embryos revealed a lack of Even-skipped (Eve) staining in Eve-expressing neurons, ectopic Eve staining in non-Eve-expressing neurons and mispositioned dorsal Eve-expressing neurons, which suggests that fru functions to maintain neuronal identity rather than to specify neuronal fate. In fru mutants these defects in axonal projections and in Eve staining were rescued by the expression of specific fru transgenes. To better understand fru's function in the formation of the embryonic CNS, I dissected out fru's function in neuron and glia through a genetic interaction study. fru genetically interacts in neurons with longitudinal lacking to make proper axonal projections. In addition, fru might be in the same genetic pathway as roundabout (robo), a repulsive guidance receptor, and commissureless, a downregulator of Robo, to ensure proper axonal pathfinding. Surprisingly, fru interacts with tramtrack and glial cells missing to repress neuronal differentiation in the lateral glia and with single-minded for the development of midline glia. Taken together, fru function is required for proper axonal pathfinding in neurons and for proper development of lateral and midline glia. / Graduation date: 2002

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No description available.