Targeted over-expression of hsp22 and the maintenance of locomotor activity of third instar larvae of Drosophila melanogaster at high temperatures
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Hsp22 has been implicated in stress tolerance and longevity in various organisms though its role in Drosophila melanogaster larval thermal tolerance has not yet been investigated. I undertook this project to determine if over-expression of hsp22 in either muscle or motor neurons could alter locomotor ability at high temperature in third instar larvae of D. melanogaster. A combination of the UAS-gal4 and tet-On promoter systems was used to over-express transgenic hsp22 in the larvae. A β-galactosidase assay was used to determine the level of gene expression following administration of different amounts of tetracycline. A concentration of 100 μg/ml of tetracycline was found to elicit appreciably higher expression of the reporter gene than 0 and 0.1 μg/ml of tetracycline. Locomotor ability of larvae was assessed at a temperature of approximately 400C by measuring the time to movement failure (TMF). Larvae that were fed 100 μg/ml of tetracycline showed a significant decline in the TMF, which could be attributed to the presence of tetracycline at a concentration of 100 μg/ml. Possible reasons behind the lack of a noticeable effect of hsp22 over-expression on the TMF are discussed. The detrimental effect of tetracycline could be attributed to the decline in mitochondrial translation or a decline in the population of endogenous bacteria, which are known to exert positive effects on the development and function of Drosophila larvae.