Oxidative Stress Responses in Arabidopsis Thaliana Plants to UV-B Irradiation

Author

Bolaji OlalereFollow

Date of Award

Fall 2024

Document Type

Thesis

Degree Name

Master of Science (MS) in Biology

Department

Biology

Committee Chair

Mijitaba Hamissou

Abstract

The depletion of the stratospheric ozone layer has led to increased levels of harmful UV-B radiation reaching the Earth's surface, posing significant challenges for plant health and development. This study investigates the oxidative stress responses in Arabidopsis thaliana when exposed to UV-B irradiation. Arabidopsis thaliana, a well-established model organism, is particularly sensitive to UV-B, making it ideal for understanding the effects of UV-B-induced oxidative stress. UV-B radiation, a mutagenic component of sunlight, disrupts key metabolic, molecular, and developmental processes, leading to DNA damage, impaired metabolism, and morphological changes. This research aims to explore how UV-B exposure affects the activities of key oxidative stress response enzymes, such as superoxide dismutase (SOD) and non-enzymatic activity, as well as heat shock proteins (Hsp-70), which play critical roles in cellular protection. Arabidopsis plants were exposed to UV-B radiation at low doses (1999 µW/Cm²) for varying durations: 30 seconds, 60 seconds, and 120 seconds, administered daily over a period of three days. Plant growth parameters were assessed, and protein responses to UV-B exposure were measured using the Bradford assay, western blotting, Total Phenolic compound and enzyme activity assays. Results suggest that UVB exposure significantly enhances the activity of antioxidant enzymes, such as superoxide dismutase (SOD), which are crucial for mitigating oxidative damage. Additionally, total phenolic compounds (TPC) increased with UV-B exposure, indicating a role for non-enzymatic antioxidants in the plant's defense mechanism. However, this research did not find any correlation between Hsp-70 upregulation and UV-B exposure. These findings highlight the complex defense mechanisms in Arabidopsis thaliana, where plants activate enzymatic and non-enzymatic antioxidant defense mechanism to UV-B exposure.