The Toxopeus lab focuses on understanding how animals and their cells survive in challenging environments, using an integrative approach. This is important for understanding how organisms tolerate current environmental stressors, and how they might respond to future changes in their environment (e.g. due to global climate change). Our work also has implications for understanding cryopreservation, an important technique for preserving cells and tissues for biomedical purposes.

Image showing that stress can affect insects at all biological levels of organization, from cells to tissues to the whole animal

Researchers in our lab learn and use many laboratory techniques, including:

  • Biochemistry: spectrophotometric assays
  • Bioinformatics: metabolomics, transcriptomics, analyzing big data
  • Cell Biology: Immunohistochemistry (IHC), live-dead staining, fluorescence microscopy, confocal microscopy
  • Cryobiology: Freezing insects and their tissues at ultra-low temperatures
  • Functional Genetics: RNA interference (RNAi) to knock down gene expression
  • Molecular Biology: RNA and DNA extractions, PCR, quantitative PCR, Western blotting

For details on our research projects, read on!

The Challenges of Freezing

Some insect species survive freezing solid, including the spring field cricket Gryllus veletis. We assume that internal ice formation is challenging, but we don’t know much about how it harms organisms at the cellular level. We use G. veletis as a model to study how low temperatures and freezing damage cells, testing the hypotheses in the graphical summary below. Interested in learning more? Read this review about insect freeze tolerance.

Hypothesized challenges associated freezing include those associated with low temperatures (e.g. loss of membrane fluidity), mechanical damage from ice (e.g. cell rupture), osmotic stress (e.g. dehydration-induced protein denaturation), and metabolic injury (e.g. oxidative damage over time)

The Biochemistry and Genetics of Freeze Tolerance

The spring field cricket Gryllus veletis substantially alters its gene expression and metabolite composition when it becomes freeze-tolerant, and previous work has suggested that several genes and small molecules (e.g. cryoprotectants) are important for surviving freezing. We use methods to manipulate gene expression (e.g. RNA interference) and cryoprotectant concentrations in these crickets to test their function in freeze tolerance (see image below) – both for survival of the whole animal and its cells. Interested in learning more? Read about previous experiments on cryoprotectants in these crickets, and/or the transcriptomics of acclimation in these crickets.


The Cell Biology of Freeze Tolerance Acclimation

The spring field cricket Gryllus veletis becomes freeze-tolerant in the Fall, allowing it to survive internal ice formation. We know that acclimation to Fall conditions (i.e. low temperatures and short days) is required for freeze tolerance in this species. However, no one has characterized the cellular changes that occur during acclimation, which could protect against the challenges associated with freezing. We use G. veletis as a model to study how animals might modify their cell biology to promote freeze tolerance, testing the hypotheses in the graphical summary below. Interested in learning more? Read about previous research on the physiology and transcriptomics of acclimation in these crickets.

Hypothesized cellular changes during acclimation include membrane and cytoskeletal remodelling, chaperone and antioxidant accumulation, decreased cell proliferation, and altered biochemical pathway activity

Overwintering Biology of Insect Pests

While many insects are beneficial to the environment and to humans (e.g. pollinators), others damage agricultural and forest plants, leading to severe economic losses. We are working to understand the overwintering biology of the apple maggot fly Rhagoletis pomonella, one of the blights of the apple industry in Nova Scotia and across North America. By improving our understanding of their basic biology, we hope to improve future attempts to control these pests. You can read about our most recent apple maggot fly paper here, and earlier cold tolerance work on pests such as the cabbage white butterfly and spotted wing drosophila (a pest of blueberries and other soft-skinned fruits).

The apple maggot fly (left; photo credit Andrew Forbes) and its impact on apple fruits (right; photo credit Whitney Cranshaw).