Diverse Mechanisms of Radiation Tolerance: Insights from Flatworms and Tardigrades

High levels of ionizing radiation represent a great danger to living cells. These damages can manifest in various ways, the most notable being the substantial harm it causes to biological DNA; in addition, the potential of ionizing radiation to impair cellular function is also of considerable concern. However, there are some organisms which show unusual resilience to harsh environments. Although many studies have been conducted on such organisms, the exact molecular mechanisms of their unusual tolerance are not entirely known, especially those associated with stem cell activity and tissue regeneration. Exploring the principles and evolutionary processes of these radiation-resistant mechanisms is crucial for studying the effects of radiation on living organisms. This review describes three model organisms that use different approaches to show various survival and adaptation patterns to irradiation with a high dose of radiation. These mechanisms include improved DNA repair and antioxidant systems, dispersed proliferation and tissue-specific radiation tolerance. Moreover, possible medical application of these unique mechanisms is considered.