Publication Date

2026

Document Type

Dissertation/Thesis

First Advisor

Sunter, Garry

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences

Abstract

Geminiviruses are economically important plant DNA viruses infecting a broad range of plant species and causing devastating crop diseases, resulting in up to 100% crop loss. As a result of these heavy losses on food and cash crops, these viruses represent a new threat to global food security and sustainability. In this research, I use Tomato golden mosaic virus (TGMV) to study host-virus relationships with an overall goal of developing sustainable and eco-friendly crop resistance. TGMV belongs to the Geminivirus subgroup, Begomovirus, that is characterized by a split genome consisting of two single-stranded circular DNAs. The TGMV genome encodes proteins necessary for viral DNA replication, encapsidation, movement and suppression of host immune responses.

Plants use RNA silencing as an antiviral defense, and geminiviruses encode the AL2 protein that acts as a viral suppressor of RNA silencing to evade this defense. Previous research has shown that AL2 interacts with rgsCaM (regulator of gene silencing-calmodulin-like protein), an endogenous regulator of RNA silencing, and relocalizes it to the nucleus. The rgsCaM protein has been shown to interact with SGS3 (suppressor of gene silencing 3) and target the protein for degradation via autophagy, resulting in suppression of post-transcriptional gene silencing (PTGS). In the nucleus, there is a homolog of SGS3, RNA-directed DNA Methylation 12 (RDM12), that plays an important role in transcriptional gene silencing (TGS), which is a host antiviral defense that targets viral DNA for methylation. I speculate that the AL2 interaction, and relocalization of rgsCaM to the nucleus targets plant RDM12 for degradation, overcoming methylation of the geminivirus genome.

Bimolecular Fluorescence complementation and Far Western Blot assays confirm an interaction between AL2 and RDM12 and that this interaction occurs in the nucleus. Electrophoretic Mobility Shift Assays demonstrate that AL2 interferes with the ability of RDM12 to bind small dsRNA, possibly inhibiting the RNA-directed DNA methylation pathway. In conclusion, my research suggests that geminivirus AL2 protein functions to evade the plant antiviral response by disrupting the activity of RDM12.

Extent

83 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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Text

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