DNA Damage and Repair Mechanisms in Duckweed (Spirodela polyrhiza) Under Ultraviolet-B (UV-B) Light Stress

Ultraviolet-B (UV-B) light exposure can harm plant growth and cellular health, causing oxidative stress and DNA damage. A study examined these effects in Spirodela polyrhiza, or duckweed, a type of aquatic plant. Duckweed seedlings were subjected to UV-B light for durations ranging from one to ten minutes, followed by recovery periods of up to 24 hours under normal conditions.

Longer UV-B exposure led to symptoms such as chlorosis, wilting, and reduced vigor. DNA damage was evident through abnormal genomic DNA in agarose gel electrophoresis, which recovered partially during the recovery phase. Immunoblot assays found increased levels of two UV-induced DNA lesions, cyclobutane pyrimidine dimers (CPDs) and 6-4 pyrimidine-pyrimidone photoproducts [(6-4)PPs], depending on the UV-B dose.

These lesions decreased after recovery, indicating the activation of DNA repair mechanisms. Peroxide staining showed a rise in hydrogen peroxide immediately after UV-B exposure, pointing to heightened oxidative stress. In summary, duckweed exhibits effective sensing, repair, and mitigation systems for UV-B-induced DNA damage, making it a promising model for studying plant DNA damage and repair mechanisms.