Rapid activation of the Arabidopsis thaliana GCN2-eIF2α module by salicylic acid: Phenotypic and translational similarities between gcn2 mutant and wild-type
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Authors
Wynn, Morgan Elizabeth
Issue Date
2025-07-31
Type
Thesis
Language
en_US
Keywords
Academic theses , Biology , Plant physiology , Plant defenses , Proteins--Synthesis , Cellular signal transduction , Plant hormones , Arabidopsis thaliana , Protein kinases
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Abstract
Salicylic acid (SA) is a natural phytohormone involved in plant development and defense against biotrophic pathogens, acting as a potent stress signaling molecule to stimulate downstream pathways for cellular resource management. While most existing literature focusses on the role of SA in gene expression at the transcriptional level (mRNA synthesis), its role in translational regulation (protein synthesis) remains under researched. While both are important, translational regulation serves as a fast method of regulating gene expression, allowing cells to rapidly adapt to quick changes in their environmental conditions. A protein kinase, General Control Nonderepressible 2 (GCN2), plays a major role in regulating protein synthesis by phosphorylating the alpha subunit of eukaryotic initiation factor 2 (eIF2), resulting in downregulation of global protein synthesis. This thesis investigates the role of SA in activating the GCN2-eIF2α module in Arabidopsis thaliana via chloroplastic reactive oxygen species (ROS). We find that SA treatment of Arabidopsis seedlings results in eIF2α phosphorylation, with dependence on GCN2, light, and photosynthesis. Surprisingly, increasing SA dosage does not correspond with increasing eIF2α phosphorylation. Additionally, wild-type and gcn2-1 knockout mutant seedlings under prolonged SA stress display similar phenotypic parameters, including fresh weight and primary root length. These findings provide insight into the signaling mechanisms of the GCN2 protein under SA stress, and suggest that alternate mechanisms may be responsible for mediating phenotypic responses to SA. Still, further research is needed to understand the translational state of plant cells in response to SA stress, as well as the direct interaction of photosynthetic byproducts with GCN2 for its activation.
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This dissertation is protected by the Copyright Laws of the United States (Public Law 94-553, revised in 1976). Consistent with fair use as defined in the Copyright Laws, brief quotations from this material are allowed with proper acknowledgement. Use of the materials for financial gain with the author's expressed written permissions is not allowed.