Abstract
BackgroundInsect diapause is an important biological process which involves many life-history parameters important for survival and reproductive fitness at both individual and population level. Drosophila montana, a species of D. virilis group, has a profound photoperiodic reproductive diapause that enables the adult flies to survive through the harsh winter conditions of high latitudes and altitudes. We created a custom-made microarray for D. montana with 101 genes known to affect traits important in diapause, photoperiodism, reproductive behaviour, circadian clock and stress tolerance in model Drosophila species. This array gave us a chance to filter out genes showing expression changes during photoperiodic reproductive diapause in a species adapted to live in northern latitudes with high seasonal changes in environmental conditions.ResultsComparisons among diapausing, reproducing and young D. montana females revealed expression changes in 24 genes on microarray; for example in comparison between diapausing and reproducing females one gene (Drosophila cold acclimation gene, Dca) showed up-regulation and 15 genes showed down-regulation in diapausing females. Down-regulation of seven of these genes was specific to diapause state while in five genes the expression changes were linked with the age of the females rather than with their reproductive status. Also, qRT-PCR experiments confirmed couch potato (cpo) gene to be involved in diapause of D. montana.ConclusionsA candidate gene microarray proved to offer a practical and cost-effective way to trace genes that are likely to play an important role in photoperiodic reproductive diapause and further in adaptation to seasonally varying environmental conditions. The present study revealed two genes, Dca and cpo, whose role in photoperiodic diapause in D. montana is worth of studying in more details. Also, further studies using the candidate gene microarray with more specific experimental designs and target tissues may reveal additional genes with more restricted expression patterns.
Highlights
Insect diapause is an important biological process which involves many life-history parameters important for survival and reproductive fitness at both individual and population level
The discovery of an adult photoperiodic reproductive diapause in Drosophila melanogaster [6,7] opened a possibility to study the role of the circadian clock genes in photoperiodic time measurement and diapause, as well as interactions between genes affecting photoperiodism and hormonal and physiological changes involved in diapause
Down-regulation of seven of the genes was specific to diapause state while in five genes the expression changes were linked with the age of the females rather than with their reproductive status (Fig. 1)
Summary
Insect diapause is an important biological process which involves many life-history parameters important for survival and reproductive fitness at both individual and population level. We created a custom-made microarray for D. montana with 101 genes known to affect traits important in diapause, photoperiodism, reproductive behaviour, circadian clock and stress tolerance in model Drosophila species. This array gave us a chance to filter out genes showing expression changes during photoperiodic reproductive diapause in a species adapted to live in northern latitudes with high seasonal changes in environmental conditions. Several insect species in temperate regions develop and reproduce during the summer, but become dormant as the winter approaches to avoid unfavourable conditions for development and reproduction This dormancy is usually linked with a period of developmental arrest, i.e. diapause, at the embryonic, larval, pupal or adult stage. Even though the reproductive diapause in D. melanogaster seems to be a relatively weak response to photoperiod and is only observed at temperatures below 14°C [7,14], the genes found to be linked with sexual maturation and diapause in this species are good candidate genes for diapause studies in more northern Drosophila species with stronger, longer-lasting photoperiodic diapause responses
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