Date of Award

2017

Publisher

North Dakota State University

Document Type

Dissertation

Degree Awarded

Doctor of Philosophy (PhD)

Program

Zoology

Department

Biological Sciences

College

Science and Mathematics

Faculty Advisor

Bowsher, Julia H.

Description

Dramatic changes in ambient temperature can have a significant impact on insect physiology throughout development. The accumulations of the deleterious physiological effects throughout low temperature exposure are collectively known as chill injury. The mechanisms underpinning the downstream physiological consequences of chill injury such as oxidative stress, perturbations in ion homeostasis, and changes in metabolism have yet to be elucidated. Brief, daily pulses of increased temperatures have been shown to repair and/or protect against the continued accumulation of chill injury, leading to an increase in survival across several insect taxa. Until recently, no transcriptomic-level assessments of gene expression during low temperature stress had been conducted. In this document I present a comparison of low-temperature stress response mechanisms across life stages in the alfalfa leafcutting bee, Megachile rotundata. RNA-seq, qPCR and oxidative stress assays were used to determine the physiological effects of low temperature exposure on two life stages: one adapted for low-temperature exposure and one that is not. Differential expression analysis revealed distinct gene expression profiles between life stages. The lack of overlap in expression profiles suggests different mechanisms are driving the response. Furthermore, an overlap in the functional classes of differentially expressed transcripts suggest that the response may be physiologically robust, even though the response is variable at the level of gene expression. Gene expression suggests oxidative stress may be a critical component in chill injury response and recovery. Antioxidant activity and lipid peroxidation, a common proxy for oxidative stress, were assessed in both life stages. M. rotundata’s ability to cope with an induced oxidative stress did not vary between treatments in either life stage. Furthermore, a lack of statistical differences between treatments in lipid peroxidative do not support the hypothesis that the benefits of fluctuating temperatures are, in part, due to reduction in oxidative stress.

Rights

NDSU Policy 190.6.2

Rights Link

https://www.ndsu.edu/fileadmin/policy/190.pdf

Author ORCID Identifier

0000-0002-5142-6162

Handle Identifier

https://hdl.handle.net/10365/28375

Download

Share

COinS