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Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Sinclair, Brent J.

Abstract

The freeze tolerant spring field cricket, Gryllus veletis, accumulates trehalose in the blood and tissues during cold acclimation. Trehalose is the main blood sugar in insects, thus its blood concentration is tightly regulated, and trehalose is readily metabolized. How do crickets modify their metabolism to accumulate trehalose in their hemolymph and tissues? I hypothesized that trehalose production, transport, and consumption were modified during the cold acclimation to facilitate trehalose accumulation. Trehalose and the trehalose-specific transporter, TRET-1, are distributed among all tissues, and trehalose accumulates in the hemolymph, fat body, Malpighian tubules, and gut. Trehalose production increases during cold acclimation via increased glycogen phosphorylase activity, facilitating trehalose accumulation. However, trehalose transport and consumption are not modified during acclimation, indicating that they are not critical for trehalose accumulation. My study furthers the understanding of trehalose distribution and the mechanism of trehalose accumulation in a freeze tolerant insect.

Summary for Lay Audience

Insect physiology is influenced by changes in temperature. Some insects mitigate the risks associated with low winter temperatures by changing their physiology to survive internal ice formation (i.e., are freeze tolerant). Many freeze tolerant insects accumulate molecules that protect cells and tissues from the direct effects of freezing. One cryoprotectant is the sugar trehalose, which is also the main insect blood sugar in insects. The spring field cricket, Gryllus veletis, accumulates trehalose in its blood and tissues when temperature and daylength decrease. Trehalose concentrations are usually tightly regulated, and it is readily metabolized into glucose for energy. I found that trehalose accumulates in all tissues except the brain and muscle during cold acclimation. How do crickets modify their metabolism to accumulate trehalose? To answer this question, I measured enzyme activity and gene expression associated with the production, transport, and consumption of trehalose. I found increased activity of glycogen phosphorylase, a key enzyme involved in trehalose synthesis, indicating that more trehalose is produced during acclimation. I found no change in expression of the trehalose transporter Tret-1 with acclimation, indicating that an increase in transportation is not critical for trehalose accumulation. Finally, I saw no change in the activity of trehalase, the enzyme responsible for cleaving trehalose into two easily metabolized glucose monomers. I conclude that increased trehalose production likely drives trehalose accumulation in G. veletis during cold acclimation, even if trehalose breakdown and transport remain unchanged.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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