Antioxidant Defenses and Poly(ADP-Ribose) Polymerase (PARP) Activity Provide “Radioresilience” Against Ionizing Radiation-Induced Stress in Dwarf Bean Plants

Exposure to ionizing radiation (IR) poses a significant risk for all organisms. Although plants are generally more resistant than animals, radiation still impacts their structure and function. Plant resistance to ionizing radiation is a pivotal property to guar- antee their survival. This study evaluates bean leaves’ early and long-term responses to oxidative stress induced by ionizing radiation. To assess the early response, we measured a battery of photosynthetic efficiency and oxidative stress markers after exposure of dwarf bean plants to X-ray doses of 0.3, 10, 50, and 100 Gy. We observed that doses started to impact photosynthetic activity at 50 Gy and that markers aggregate in two kinds of behaviors. To test the capacity to recover from radiation-induced damages, 50 Gy-irradiated plants were evaluated with the same markers 3-, 10-, 12-, and 20-days post-irradiation. Dwarf beans displayed remarkable resilience, recovering photosynthetic activity to pre-stress level after three days and pigment content after ten days. The remodulation of oxidative stress markers is slower and more complex, with catalase and total polyphenols failing to recover completely and residual antioxidant activity after twenty days. Despite that, PARP activity recovers to pre-irradiation after three days. The restoration of photosynthesis to pre-irradiated conditions highlights the DNA-repairing efficiency of poly(ADP-ribose) polymerase and antioxidant machinery in providing resilience to radiation-induced oxidative stress. Understanding resilience mechanisms sheds light on the ability of plants to survive and thrive in radiation-intense environments, such as space or radioactively contaminated areas.