Genome-wide transcriptome profiling of ROS scavenging and signal transduction pathways in rice (Oryza sativa L.) in response to different types of ionizing radiation

Ionizing radiation directly and indirectly affects gene expression within the plant genome. To access the antioxidant response of rice to different types of ionizing radiation, rice seeds were exposed to gamma-ray, cosmic-ray and ion beam radiation. Exposure to ionizing radiation dramatically decreased the shoot length in all plants but not the root length compared with a non-irradiated plant. Electron spin resonance, confirmed that the number of free radicals in cell was greatly increased by different types of ionizing radiation. The measurement of the MDA, chlorophyll, carotenoids contents and activity of antioxidant enzymes revealed that gamma-ray and cosmic-ray, but not ion beam, ionization deceased chlorophyll and carotenoids contents, while all three ionization treatments increased the activities of peroxidase, ascorbate peroxidase, and superoxide dismutase compared with the non-irradiated plants. Microarray analysis using Affymetrix GeneChip was used to establish the gene transcript profiles of rice genes regarding ROS scavenging and signal transduction pathways after ionization treatment. Many of the rice genes involved in ROS scavenging and signal transduction pathways showed induction or repression that had increased more than twofold after ionization treatment. In particular, genes associated with electron transport, such as NADPH oxidase-like and alternative oxidase, were often down-regulated by more than twofold in response to the ionization treatments. In our transcriptomic profile analysis, we confirmed that the expression of rice genes associated with ROS scavenging and signal transduction pathways was induced or repressed to different degrees by the different types of ionizing radiations, as in other environmental stresses.