Molecular Targets of Thermal Stress During Development
Sudden changes in the environment can disrupt cellular processes. Cells possess damage-control mechanisms to cope with these environmental “stresses”, and thus exhibit some tolerance to such external insults. But cells can also be quite vulnerable. In the context of development, embryos must execute a programmed set of rapid mitotic divisions. How do embryos orchestrate these mitotic divisions and maintain normal development in the face of environmental stress?
We are approaching this question by testing the role of specific candidate genes to confer thermal tolerance during development in the fruit fly Drosophila melanogaster. In particular, we are investigating how gene-specific maternal effects influence cellular phenotypes and whole-organism survival during and after temperature stress (For more info check out our new manuscript -- In press at Journal of Experimental Biology -- on bioRxiv here). This system will allow us to probe cellular phenotypes related to environmental stress under the microscope in real time. Our goal is to define the link between gene expression and the maintenance of critical cellular structures. This research will have a broad impact by contributing to our basic knowledge of how cells respond to environmental stress and by identifying candidate pathways that are the basis of stress tolerance at both the cellular and whole-organism levels. Moreover, these techniques are applicable to organisms other than just fruit flies and can be used to study the effects of environmental stress at the cellular level in many different species.
Life-stage-specific patterns of thermal adaptation
Many terrestrial ectothermic species exhibit limited variation in upper thermal tolerance across latitude. However, these trends may not signify limited adaptive capacity to increase thermal tolerance in the face of climate change. Instead, thermal tolerance may be similar among populations because behavioral thermoregulation by mobile organisms or life stages may buffer natural selection for thermal tolerance. We are comparing thermal tolerance of adults and embryos among natural populations of Drosophila melanogaster from a broad range of thermal habitats around the globe to assess natural variation of thermal tolerance in mobile vs. immobile life stages. Amazingly, we find no variation among populations in adult thermal tolerance, but embryonic thermal tolerance is higher in tropical strains than in temperate strains. Our findings suggest that thermal selection has led to divergence in embryonic thermal tolerance but that selection for divergent thermal tolerance may be limited in adults. Further, our results suggest that thermal traits should be measured across life stages in order to better predict adaptive limits. For more information check out our new manuscript on bioRxiv: here.