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Virginia Walker

 
  Genetics and molecular biology of insect development

 
  Contact Information:  
  Professor of Biology

Tel: (613) 533-6123
Fax: (613) 533-6617
email: walkervk@biology.queensu.ca


 
  Our research interests concern the regulation of gene expression during development and in response to environmental and chemical stress. We address this problem in insects in two related, and overlapping, efforts.

The control of gene expression and resistance: Our hypothesis is that insects can adapt to a variety of natural and humanly modified conditions by the overproduction of target proteins as a consequence of specific gene amplifications. Such phenomena are well known in mammalian cells and tumors. In opposition to this drive to amplify, however, there have been strong selective forces to streamline the genome of some insects. In order to investigate this conundrum we have examined the molecular genetic basis of resistance in Drosophila and Heliothis to an anti-cancer drug and to the environmental stresses of cold and desiccation in Drosophila, in the Tenebrio beetle and in spruce budworm as well as thermo-tolerance in locusts (with Dr. M. Robertson, Biology). This work has led to the isolation and cloning of the first insect antifreeze protein genes (with Dr. P. Davies, Biochemistry) and an interest in their structure and interactions (with Dr. Z. Jia, Biochemistry and Dr. J. Ripmeester, NRC).

Gene regulation: Development is regulated by the action of three major groups of hormones; two of these, the ecdysteroids and juvenile hormone, are of interest to us.

Developmentally responsive genes are being studied in beetles, in locusts (with Dr. G. Wyatt, Biology) and spruce budworm. The analysis of gene regulation is facilitated by the introduction of genomic DNA into Drosophila cell lines or, using transposable elements (with Dr. S. Whyard, Australia), into Drosophila and beetle embryos. These experiments are also used in the investigation of the transfer of various resistant phenotypes to susceptible insects.



 
  Publications:  
  Selected publications (1998-2001)

1. Misener, S. and Walker, V.K. (2001) Complementation cloning and characterization of the pyrroline 5-carboxylate reductase gene from Drosophila melanogaster. Biochem. Genetics 39: 15-31.

2. Zhou, S., J. Zhang, M. Hirai, Y. Chinzei, H. Kayser, G.R. Wyatt and V.K. Walker (2001) A locust DNA-binding protein involved in gene regulation by juvenile hormone. Molec. Cellular Endocrinol. in press

3. Wu, B.S., V.K. Walker and R.M. Robertson (2001) Heat-shock-induced spike broadening and thermoprotection in the locust flight system. J. of Neurophysiol. in press

4. Kuiper, M.J., P.L. Davies and V.K. Walker (2001) A theoretical model of a plant antifreeze protein from Lolium perenne. Biophys. J. in press

5. Misener, S. and V.K. Walker (2001) Cold tolerance and proline metabolic gene expression in Drosophila melanogaster. J. Insect Physiol. 47:393-400.

6. Duncker, B.P., Rancourt, D.E., Tyshenko, M.G., Davies, P.L. and Walker V.K. (2001) Drosophila as a model organism for the transgenic expression of antifreeze proteins. Cell and Molecular Responses to Stress II Chapter 2.

7. Graether, S.P., Kuiper, M.J., GagnÈ, S.M., Walker, V.K., Jia, Z., Sykes, B.D. and Davies, P.L. (2000) _-Helix structure and ice-binding properties of a hyperactive antifreeze protein. Nature 406:325-326.

8. Misener, S. and Walker V.K. (2000) Extraordinary high density of unrelated genes showing overlapping and intraintronic transcription units. Biochim. Biophys. Acta 1492:269-270

9. Liou, Y-C., Daley, M., Graham, L., Kay, C.M., Walker, V.K., Sykes, B.D. and Davies, P.L. (2000) Folding and structural characterization of highly disulfide-bonded beetle antifreeze protein produced in bacteria. Protein Expression & Purification 19: 148-157.

10. Walker, V.K., Tyshenko, M.G., Kuiper, M.J., Dargar, R.V., Yuhas, D.A., Cruickshank, P.A., Chaguturu, R. (2000) Tobacco budworm dihydrofolate reductase is a promising target for insecticide discovery. Eur. J. Biochem. 267:394-403.

11. Doucet, D., M.G. Tyshenko, M.J. Kuiper, S.P. Groether, B.D. Sykes; A.J. Daugulis, P.L. Davies and V.K. Walker (2000) Structure-function relationships in spruce budworm antifreeze protein revealed by isoform diversity. Eur. J. Biochem 267: 6082-6088.

12. Graham, L.A., V.K. Walker and P.L. Davies (2000) Developmental and environmental regulation of antifreeze proteins in the mealworm beetle Tenebrio molitor. Euro J. Biochem 267: 6452-6458.

13. Edwards, M.J., L.A. Moskalyk, V.K. Walker and M. Jacobs-Lorena (2000) Carboxypeptidase A in Aedes aegypti is midgut-specific. Insect Mol. Biol. 9:33-38.

14. Liou, Y-C., P. Thibault, V.K. Walker, P.L. Davies and L.A. Graham (1999) Acomplex family of highly heterogeneous and internally repetitive hyperactive antifreeze proteins from the beetle Tenebrio molitor. Biochemistry 38:11415-11424.

15. Duncker, B., P.L. Davies and V.K. Walker (1999) Antifreeze protein activity is augmented by increased gene dosage in transgenic Drosophila. Trans. Res. 8:45-50.

16. Saleh, D., J. Zhang, G.R. Wyatt and V.K. Walker (1998) Cloning and characterization of an ecdysone receptor cDNA from Locusta migratoria. Molec. And Cell. Endocrin. 143:91-99.

17. Gauthier, S. Y., C. M. Kay, B.D. Sykes, V.K. Walker and P.L. Davies (1998) Disulfide bond mapping and structural characterization of spruce budworm antifreeze protein. Eur. J. Biochem. 258:445-453.