Photosynthetic response of Scenedesmus quadricauda to carbon ions irradiation

Abstract Plants and algae are one of the key components in Controlled Ecological Life Support System (CELSS) in long-term manned space exploration. However, the biological effects of high linear energy transfer (LET) cosmic radiation on algae are even less well characterized. The photosynthetic apparatus is one of the most sensitive targets after radiation. In this study we analyzed the chlorophyll fluorescent parameters (Fv/Fm, φPSII, and NPQ), the photoprotective pigment lutein, and the transcriptional expression of Lhcb1 and Lhcb2 in a green microalgae, Scenedesmus quadricauda after exposure to 12C6+ ions that were provided by the Heavy- Ion Research Facility in Lanzhou (HIRFL), China. Scenedesmus quadricauda has rapid growth rate and is rich in high-value products which are essential for CELSS development. The results showed that low photosynthetic efficiency of Scenedesmus quadricauda was found in the 60 Gy group within 2 h after radiation. The thermal dissipation abilities of Scenedesmus quadricauda were stronger after exposure to 20 Gy and 60 Gy group within 2 h. Meanwhile, the transcriptional expressions of Lhcb1 and Lhcb2 were up-regulated after exposure to 20 Gy of carbon ions within 4 h. Therefore, 20 Gy of carbon ions radiation could cause stimulative effects on the photoprotective ability and transcriptional regulation of the major LHCII antenna proteins in Scenedesmus quadricauda. Our findings provide the first insight into the biological effects involved in heavy ions radiation on the photosynthetic activity of Scenedesmus quadricauda.