Detoxification mechanisms underlying chemical adaption in the honey bee (Apis mellifera) and two-spotted spider mite (Tetranychus urticae)
Restricted (Penn State Only)
- Author:
- Koirala B K, Sonu
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 12, 2024
- Committee Members:
- Gary Felton, Program Head/Chair
Kelli Hoover, Major Field Member
John Tooker, Major Field Member
Fang Zhu, Chair & Dissertation Advisor
Heather Hines, Outside Unit & Field Member - Keywords:
- metabolic detoxification
host adaptation
oxidative stress
pesticide resistance
enzymes - Abstract:
- As generalist pollinators, honey bees have the potential to be exposed to a broad diversity of agrochemicals and plant allelochemicals. This study explores the significance of detoxification enzymes in honey bees (Apis mellifera), which can metabolize or sequester toxic chemicals and protect honey bee health against these compounds. In Chapters II and III, I conducted a comprehensive functional and structural characterization of AmGSTD1 and AmGSTO1, the only delta and omega class glutathione S-transferases (GSTs) in the honey bee genome, to unravel their roles in agrochemical detoxification and antioxidative stress responses in the honey bees. I determined the 3-dimensional (3D) structures of these honey bee GSTs using x-ray crystallography, providing insights into their molecular structures. My findings demonstrate that AmGSTD1 and AmGSTO1 exhibit significant binding capabilities towards various herbicides, fungicides, insecticides, and their derivatives, suggesting their potential roles in either metabolizing or sequestering these chemicals. Moreover, my investigation revealed the potential of these enzymes to mitigate oxidative stress induced by agents like cumene hydroperoxide, hydrogen peroxide, and paraquat. The overall findings of these two chapters suggest that honey bee GSTs serve as important detoxification enzymes that contribute to xenobiotic adaptation in bees. In Chapter IV, I elucidated the mechanisms underlying acaricide resistance in populations of two-spotted spider mite (TSSM; [Tetranychus urticae]). The susceptible TSSM specimens were collected from a hopyard in Prosser, WA, United States in summer 2015. This population was then subjected to laboratory selection with increasing doses of abamectin and bifenthrin to develop resistance. Subsequently, a comparative transcriptomic analysis using RNA sequencing was performed. My analysis revealed a significant number of both downregulated and upregulated genes in the resistant TSSM populations compared to the susceptible ones. Specifically, upregulated genes in the resistant populations were associated with metabolism of xenobiotics, including genes encoding cytochrome P450 monooxygenases, glutathione S-transferases, carboxylesterases, uridine diphosphate (UDP)-glycosyltransferases, lipocalin, and peptidases. Furthermore, my study identified functionally important mutations in detoxification enzymes that may play important roles in facilitating acaricide resistance in TSSM populations infesting hops. These findings can aid in developing molecular tools to detect and monitor acaricide resistance in the field, enabling better planning for the effective use of acaricides to break or slow down resistance buildup.