First Advisor

Gomez, Susana K.

First Committee Member

James, Andrea

Second Committee Member

Tamborindeguy, Cecilia

Third Committee Member

Argueso, Cris

Degree Name

Doctor of Philosophy

Document Type

Dissertation

Date Created

8-2025

Department

College of Natural and Health Sciences, Biological Sciences, Biological Sciences Student Work

Embargo Date

8-2027

Abstract

Aphids, including the pea aphids (Acyrthosiphon pisum), are major agricultural pests due to their ability to damage crops and transmit plant viruses. Understanding the molecular interactions between aphids and their host plants is crucial for developing sustainable pest management strategies. This dissertation examines the complex relationships among pea aphids, host plants, and arbuscular mycorrhizal (AM) fungi, focusing on transcriptomic changes in both aphids and plants during feeding.

Chapter II investigates how factors such as feeding duration, aphid tissue type, aphid age, and host plant species affect the expression of aphid salivary effector genes, which are key to suppressing plant defenses and facilitating nutrient uptake. The study found that these factors significantly influence effector gene expression. Younger aphids and those in early feeding stages showed higher expression levels, with notable differences depending on the host plant. Additionally, small changes in gene expression are not captured when using whole aphid bodies compared to heads, highlighting the importance of tissue selection in transcriptomic studies.

Chapter III explores how AM fungal colonization of Medicago truncatula indirectly affects the aphid salivary transcriptome during feeding. The research revealed that AM symbiosis significantly alters aphid gene expression, particularly pathways related to proteolysis, nutrient uptake, and stress adaptation, especially during the early stages of feeding (six hours). At this timepoint, 151 genes were differentially expressed, with a majority upregulated. After 24 hours, transcriptomic changes were less pronounced, suggesting aphid adaptation to mycorrhizal plant physiology. Notably, aphids feeding on mycorrhizal plants for 24 hours exhibited enhanced performance, indicating potential benefits from this interaction.

Chapter IV compares the foliar transcriptome of mycorrhizal and non-mycorrhizal M. truncatula during aphid herbivory. The findings show that mycorrhizal plants prioritize structural and metabolic defenses over induced pathogen defenses, with significant suppression of secondary metabolism and upregulation of lipid-based and structural defenses. These trends persist over 24 hours, suggesting a resource allocation trade-off favoring stress tolerance and structural defense mechanisms.

Overall, this research provides critical insights into the molecular mechanisms underlying aphid-host plant-AM fungi interactions. The findings highlight potential avenues for developing sustainable pest management strategies by leveraging AM-induced plant defenses while advancing our understanding of inter-kingdom interactions that influence agricultural ecosystems.

Abstract Format

html

Places

Greeley, Colorado

Extent

224 pages

Local Identifiers

Irvin_unco_0161D_11369

Rights Statement

Copyright is held by the author.

Digital Origin

Born digital

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Available for download on Sunday, August 01, 2027

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