The Effects of Temporal Cold Exposure and Caste Differences on Gene Expression and Epigenetics of Common Bumble Bee Species

Under harsh environmental conditions, such as cold stress, organisms must quickly be able to mount an appropriate response to minimize injury and avoid death. Molecular mechanisms offer a rapid method to help mitigate effects of cold exposure. However, more research is needed to better understand the timing of these processes and what governs them. Here I present work assessing the cold-induced molecular responses of bumble bees, a genus common across North America with morphological and physiological characteristics adapted for cooler environments. I first investigated cold-induced temporal gene expression changes in a common eastern species, Bombus impatiens. Findings suggest that differential gene expression of thoracic muscles peaked 10 minutes after chill coma recovery and was primarily characterized by metabolic shifts favoring the production and use of glucose for energy. Gene expression differences diminished after 30 minutes, with no long-term expression markers detected. Next, I explored how the epigenetic mechanism, DNA methylation, potentially influenced temporal gene expression changes under cold stress in the western species, Bombus vosnesenskii. The brains appeared to have more robust transcriptional shifts and methylation repatterning across the time series compared to the thoric muscles, and 10 minutes post-chill coma is when most molecular changes occurred. Differential gene expression of the brains related to immune pathway activation, while methylation repatterning of the brains and muscles was associated with cellular communication. Network analyses failed to identify significant correlations between gene expression and methylation, suggesting methylation may not directly influence the differential expression of the genes responding to cold exposure in B. vosnesenskii. However, genes with low to moderate levels of methylation had higher, more stable levels of expression compared to unmethylated genes with more variable gene expression. I further extended the study of methylation to investigate tissue and caste level differences between queen and workers of the western species, Bombus vancouverensis. Methylation levels were highest in the brains and lowest in the ovaries of queens. Most differentially methylated sites/genes were observed from the comparisons of the brains, thoracic muscles, and ovaries to each other. Gene ontologies associated with the between-caste comparisons primarily involved developmental pathway differences.

Grantor dc:publisher

University of Alabama Libraries

Year dc:date.issued

2025

Author dc:creator

• Verble, Kelton Mychael

Advisor dc:contributor.advisor

• Lozier, Jeffrey D.

Contributors dc:contributor

• Dillon, Michael E.
• Fierst, Janna L.
• McKain, Michael R.
• Benstead, Jonathan P.

• Bombus
• Caste Differentiation
• Chill coma
• Cold exposure
• DNA methylation
• Gene expression

Statement dc:rights

• All rights reserved by the author unless otherwise indicated.

Language dc:language.iso

en_US, English

Dc Identifier Other

1206101

OAI identifier oai:identifier

oai:ir.ua.edu:123456789/17633