No abstract

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.

Black soybean (Glycine max L.) has been used as a traditional medicine because its seed coat contains various natural phenolic compounds such as anthocyanins. The objective of this study was to reveal the genetic variation in the agricultural traits, phytochemicals, and antioxidant activity of 172 Korean black soybean landraces (KBSLs) and establish a relationship among them. The evaluation of three agricultural traits (days to 50% flowering, maturity, and 100-seed weight), six phytochemicals (delphinidin-3-glucoside, cyaniding-3-glucoside, petunidin-3-glucoside, daidzin, glycitin, and genestin), and four antioxidant activities (2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2 -azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS), ferric-reducing antioxidant power (FRAP), and the total polyphenol content (TPC) of 172 KBSLs were analyzed in 2012 and 2015. The agricultural traits, phytochemicals, and antioxidant activities of the 172 KBSLs showed wide variation among the accessions and years. In correlation analysis, the agricultural traits and phytochemicals showed positive and negative correlations with phytochemicals and antioxidant activity, respectively. The principal component analyses result indicated that phytochemicals accounted for most of the variability in the KBSLs. In clustering analysis, the 172 KBSLs were classified into four clusters. These results could lead to expanding the knowledge of the agricultural traits, phytochemicals, and antioxidant activity of the KBSLs, which are valuable materials for the development of new soybean varieties.

Ionizing radiation (IR) affects gene expression from plant genomes. To monitor the genome-wide transcriptional changes induced by three types of IR, we used the rice Affymetrix GeneChip microarray to identify genes that are up- or down-regulated by gamma rays (GAs), cosmic rays (CRs) and ion beams (IBs). The overall expression patterns in rice seedlings generated from seeds exposed to GAs and IBs were similar but differed for CRs exposure. Expression profiles of genes involved in metabolic pathways and cellular response were identified using MapMan analysis. This result revealed that IRs induced gene expression related to sucrose-starch metabolisms; sugar and starch accumulation was significantly increased in response to three types of IR in rice. In addition, we compared the genes commonly up- or down-regulated by exposure to three types of IR and identified 53 candidate radio marker genes (RMGs) that were differentially regulated by radiation exposure but not by other stresses. Among these genes, we selected six RMGs commonly applicable to different types of IR by specific coexpression networks using the algorithm for the reconstruction of accurate cellular networks (aracne) and confirmed the expression of these genes by reverse transcription-polymerase chain reaction (RT-PCR) analysis. Our results provided insight into the mechanisms of the responses to different types of IR and identified multiple marker genes to predict sensitivity to three types of IR.

In this study, gamma rays were used to irradiate embryogenic calli induced from cotyledon explants of Panax ginseng Meyer. After the embryogenic calli were irradiated, they were transferred to adventitious roots using an induction medium; next, mutated adventitious root (MAR) lines with a high frequency of adventitious root formations were selected. Two MAR lines (MAR 5-2 and MAR 5-9) from the calli treated with 50 Gy of gamma rays were cultured on an NH4NO3-free Murashige and Skoog medium with indole-3-butyric acid 3 mg/L. The expression of genes related to ginsenoside biosynthesis was analyzed using reverse transcription polymerase chain reaction with RNA prepared from native ginseng (NG), non-irradiated adventitious root (NAR) and 2 MAR lines. The expression of the squalene epoxidase and dammarenediol synthase genes was increased in the MAR 5-2 line, whereas the phytosterol synthase was increased in the MAR 5-9 line. The content and pattern of major ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rf, and Rg1) were analyzed in the NG, NAR, and 2 MAR lines (MAR 5-2 and MAR 5-9) using TLC and HPLC. In the TLC analysis, the ginsenoside patterns in the NG, NAR, and 2 MAR lines were similar; in contrast, the MAR 5-9 line showed strong bands of primary ginsenosides. In the HPLC analysis, compared with the NG, one new type of ginsenoside was observed in the NAR and 2 MAR lines, and another new type of ginsenoside was observed in the 2 MAR lines irradiated with gamma rays. The ginsenoside content of the MAR 5-9 line was significantly greater in comparison to the NG.