| In nature, animals are often subjected to periods of sub-optimal food resources. Characteristic responses to starvation stress have been observed in bacteria, nematodes and yeast: they alter their morphology, become quiescent, and suspend reproduction until adequate food resources become available. Studies of laboratory and natural populations of Drosophila reveal a surprising amount of genetic variation for starvation tolerance. The presence of this genetic variation is an evolutionary puzzle, as variability would not be expected in a key trait related to individual survival. While starvation resistance has been positively correlated with lifespan and other stresses, it is often negatively correlated with fecundity, suggesting that a trade-off between reproduction and individual survival might be present. In order to evaluate this hypothesis, the suite of genes affecting starvation resistance and their properties must be known. Three complementary methods were used to identify genes affecting starvation resistance: a P-element insertional mutagenesis screen, which directly identifies candidate genes involved in the response to starvation stress; deficiency complementation mapping, which reveals small genomic regions contributing to variation in starvation resistance; and transcriptome analysis using microarrays, which has the potential to identify both types of genes.;The starvation tolerance phenotype was assessed for 933 P-element insertion lines in two isogenic backgrounds: Canton-S and Samarkand. 383 insertions had a significant effect on starvation tolerance. The effect of the P-element inserts was generally negative and often sex-specific. Only 31 insertions significantly increased starvation tolerance. Significant insertions tag genes that are putatively involved in the starvation stress response.;Deficiency complementation mapping was used to fine-map broad genomic regions (quantitative trait loci, or QTL) previously identified for starvation resistance. The five original QTL fractionated into thirteen smaller QTL, six of which had sex specific effects. From these fine-mapped regions 26 genes were chosen for mutation complementation testing. Twelve of the 26 genes showed a significant effect on variation in starvation resistance between the two wild-type strains, Oregon-R and 2b. (Abstract shortened by UMI.). |
