Converting low dose radiation to redox signaling.

In contrast to the damaging effects of high doses, low dose radiation (UV, gamma) has been reported to provoke constructive changes in plants. However, the mechanisms by which plants recognize and respond to low dose radiation are not understood. We have shown recently that polygalacturonic acid, cell wall polysaccharide, converts the highly reactive product of radiation - hydroxyl radical into superoxide which may be further dismutated to hydrogen peroxide. Superoxide has been proposed to act as a signaling molecule, while hydrogen peroxide is known to be the key species in redox signaling cascades which are involved in the regulation of various physiological processes. Hence we propose that polygalacturonic acid may operate as radiation-signaling convertor. The outlined principles of radiation-sensing could also be valid for mammalian cells, with some other molecules mediating the conversion.