Effect of gamma irradiation on physiological and proteomic changes of Arctic Zygnema sp. (Chlorophyta, Zygnematales)

In this study, the effect of ionizing radiation on an Arctic alga was examined by assessing photosynthetic efficiency, antioxidant capacity, and proteomic changes. Arctic Zygnema sp. was gamma-irradiated at doses of 1, 3, and 5 kGy and showed serious cell damage after irradiation with the 5 kGy dose. The photosynthetic efficiency markedly decreased in gamma-irradiated Zygnema sp.; whereas, antioxidant capacity significantly increased. To investigate changes in protein expression levels, two-dimensional electrophoresis was performed. Thirty-nine protein spots were differently expressed. Several proteins, both upregulated and downregulated, were identified as photosynthesis-related proteins, confirming an important effect of gamma irradiation on the photosynthetic process. On the one hand, proteins similar to those involved in energy metabolism, isoprene biosynthesis, and protein biosynthesis were significantly downregulated. On the other hand, proteins related to DNA repair, quinone oxireductase, regulation of microtubules, and cell wall biogenesis were upregulated in gamma-irradiated Zygnema sp. These results provide insights on the effects of gamma irradiation on Zygnema sp. that can aid the interpretation of response mechanisms of Arctic algae to ionizing radiation.