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Mishra S, Duarte GT, Horemans N, Ruytinx J, Gudkov D, Danchenko M. Complexity of responses to ionizing radiation in plants, and the impact on interacting biotic factors. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 924:171567. [PMID: 38460702 DOI: 10.1016/j.scitotenv.2024.171567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 02/20/2024] [Accepted: 03/06/2024] [Indexed: 03/11/2024]
Abstract
In nature, plants are simultaneously exposed to different abiotic (e.g., heat, drought, and salinity) and biotic (e.g., bacteria, fungi, and insects) stresses. Climate change and anthropogenic pressure are expected to intensify the frequency of stress factors. Although plants are well equipped with unique and common defense systems protecting against stressors, they may compromise their growth and development for survival in such challenging environments. Ionizing radiation is a peculiar stress factor capable of causing clustered damage. Radionuclides are both naturally present on the planet and produced by human activities. Natural and artificial radioactivity affects plants on molecular, biochemical, cellular, physiological, populational, and transgenerational levels. Moreover, the fitness of pests, pathogens, and symbionts is concomitantly challenged in radiologically contaminated areas. Plant responses to artificial acute ionizing radiation exposure and laboratory-simulated or field chronic exposure are often discordant. Acute or chronic ionizing radiation exposure may occasionally prime the defense system of plants to better tolerate the biotic stress or could often exhaust their metabolic reserves, making plants more susceptible to pests and pathogens. Currently, these alternatives are only marginally explored. Our review summarizes the available literature on the responses of host plants, biotic factors, and their interaction to ionizing radiation exposure. Such systematic analysis contributes to improved risk assessment in radiologically contaminated areas.
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Affiliation(s)
- Shubhi Mishra
- Institute of Plant Genetics and Biotechnology, Plant Science and Biodiversity Centre, Slovak Academy of Sciences, 950 07 Nitra, Slovakia
| | - Gustavo Turqueto Duarte
- Unit for Biosphere Impact Studies, Belgian Nuclear Research Centre SCK CEN, 2400 Mol, Belgium
| | - Nele Horemans
- Unit for Biosphere Impact Studies, Belgian Nuclear Research Centre SCK CEN, 2400 Mol, Belgium; Centre for Environmental Sciences, Hasselt University, 3590 Diepenbeek, Belgium
| | - Joske Ruytinx
- Department of Bio-engineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Dmitri Gudkov
- Institute of Hydrobiology, National Academy of Sciences of Ukraine, 04210 Kyiv, Ukraine
| | - Maksym Danchenko
- Institute of Plant Genetics and Biotechnology, Plant Science and Biodiversity Centre, Slovak Academy of Sciences, 950 07 Nitra, Slovakia.
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Impact of Proton Beam Irradiation on the Growth and Biochemical Indexes of Barley ( Hordeum vulgare L.) Seedlings Grown under Salt Stress. PLANTS 2020; 9:plants9091234. [PMID: 32962044 PMCID: PMC7570119 DOI: 10.3390/plants9091234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 09/10/2020] [Accepted: 09/17/2020] [Indexed: 11/17/2022]
Abstract
The present paper examines the effects of salt stress on the growth, pigments, lipid peroxidation and antioxidant ability of barley (Hordeum vulgare L.) seedlings raised from proton beam irradiated caryopses. In order to assess the effects of radiation on the early stages of plant growth and analyze its possible influence on the alleviation of salinity, 3 and 5 Gy doses were used on dried barley seeds and germination occurred in the presence/absence of NaCl (100 mM and 200 mM). After treatment, photosynthetic pigments increased in the 5 Gy variant, which registered a higher value than the control. Among the antioxidant enzymes studied (SOD, CAT, and POD) only CAT activity increased in proton beam irradiated seeds germinated under salinity conditions, which indicates the activation of antioxidant defense. The malondialdehyde (MDA) content declined with the increase of irradiation doses on seeds germinated at 200 mM NaCl. On the other hand, the concentration of 200 mM NaCl applied alone or combined with radiation revealed an increase in soluble protein content. The growth rate suggests that 3 Gy proton beam irradiation of barley seeds can alleviate the harmful effects of 100 mM NaCl salinity, given that seedlings' growth rate increased by 1.95% compared to the control.
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Deoli NT, Hasenstein KH. Irradiation effects of MeV protons on dry and hydrated Brassica rapa seeds. LIFE SCIENCES IN SPACE RESEARCH 2018; 19:24-30. [PMID: 30482278 DOI: 10.1016/j.lssr.2018.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/27/2018] [Accepted: 08/15/2018] [Indexed: 06/09/2023]
Abstract
Although space radiation is a known risk for space travel and eventual colonization of Moon or Mars, relatively few data exist on radiation effects on potential crop plants. We studied Brassica rapa to assess the tolerance of seeds and seedlings to radiation by exposing dry and hydrated B. rapa seeds to 1, 2 and 3 MeV proton ions of various fluences and examined the effect on germination and root growth. Modeling penetration depth with SRIM code indicated that the applied energy was insufficient to penetrate the seeds; therefore, all energy was deposited into the tissue. Subsequent germination varied based on the incident ion energy and fluence (dose). Dry and hydrated seeds germinate after ion fluence (1013 ions cm-2) irradiation, but the germination percentage decreased with increasing fluence for ions that could penetrate the seed coat (> 1 MeV). Despite their greater volume and mass, hydrated seeds were more sensitive to irradiation than dry seeds. Damage of the seed coat after irradiation led to faster germination and initial seedling growth. Our results suggest that the seed coat represents a valuable natural radiation protection and that low energy protons, the prevailing solar radiation, are suitable for studying radiation effects in seeds and plants.
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Affiliation(s)
- Naresh T Deoli
- Louisiana Accelerator Center, University of Louisiana at Lafayette, Lafayette, LA, 70504-43600, USA
| | - Karl H Hasenstein
- Louisiana Accelerator Center, University of Louisiana at Lafayette, Lafayette, LA, 70504-43600, USA; Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504-43602, USA.
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Zhao Q, Wang W, Gao S, Sun Y. Analysis of DNA methylation alterations in rice seeds induced by different doses of carbon-ion radiation. JOURNAL OF RADIATION RESEARCH 2018; 59:565-576. [PMID: 30020485 PMCID: PMC6151634 DOI: 10.1093/jrr/rry053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/08/2018] [Indexed: 06/08/2023]
Abstract
To investigate the mechanism underlying differences in biological effects induced by low- versus high-dose heavy-ion radiation (HIR) in rice plants, two-dimensional gel electrophoresis (2-DE) coupled with methylation-sensitive amplification polymorphism (MSAP) analysis were used to check the expression changes in rice leaf proteome profiles and the changes in DNA methylation after exposure of seeds to ground-based carbon-ion radiation at various cumulative doses (0, 0.01, 0.02, 0.1, 0.2, 1, 2, 5 or 20 Gy; 12C6+; energy, 165 MeV/u; mean linear energy transfer, 30 KeV/μm). In this study, principal component analysis (PCA) and gene ontology (GO) functional analysis of differentially expressed proteins of rice at tillering stage showed that proteins expressed in rice samples exposed to 0.01, 0.02, 0.1, 0.2 or 1 Gy differed from those exposed to 2, 5 or 20 Gy. Correspondingly, the proportion of hypermethylation was higher than that of hypomethylation at CG sites following low-dose HIR (LDR; 0.01, 0.2 or 1 Gy), whereas this was reversed at high-dose HIR (HDR; 2, 5 or 20 Gy). The hypomethylation changes tended to occur at CHG sites with both low- and high-dose HIR. Furthermore, sequencing of MSAP variant bands indicated that the plants might activate more metabolic processes and biosynthetic pathways on exposure to LDR, but activate stress resistance on exposure to HDR. This study showed that radiation induced different biological effects with low- and high-dose HIR, and that this may have been caused by different patterns of hyper- and hypomethylation at the CG sites.
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Affiliation(s)
- Qian Zhao
- Institute of Environmental System Biology, College of Environmental Science and Engineering, Dalian Maritime University, Dalian, PR China
| | - Wei Wang
- Institute of Environmental System Biology, College of Environmental Science and Engineering, Dalian Maritime University, Dalian, PR China
| | - Shuai Gao
- Institute of Environmental System Biology, College of Environmental Science and Engineering, Dalian Maritime University, Dalian, PR China
| | - Yeqing Sun
- Institute of Environmental System Biology, College of Environmental Science and Engineering, Dalian Maritime University, Dalian, PR China
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Ariyoshi K, Miura T, Kasai K, Akifumi N, Fujishima Y, Yoshida MA. Radiation-induced bystander effect in large Japanese field mouse (Apodemus speciosus) embryonic cells. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2018; 57:223-231. [PMID: 29785486 DOI: 10.1007/s00411-018-0743-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 05/17/2018] [Indexed: 06/08/2023]
Abstract
Although evidence suggests that ionizing radiation can induce the bystander effect (radiation-induced bystander effect: RIBE) in cultured cells or mouse models, it is unclear whether the effect occurs in cells of wild animals. We investigated medium-mediated bystander micronucleus (MN) formation and DNA damage in un-irradiated cells from a large Japanese field mouse (Apodemus speciosus). We isolated four clones of A. speciosus embryonic fibroblasts (A603-1, A603-2, A603-3, and A603-4) derived from the same mother, and examined their radiation sensitivity using the colony-forming assay. A603-3 and A603-4 were similar, and A603-1 and A603-2 were highly sensitive compared with A603-3 and A603-4. We examined RIBE in the four clones in autologous medium from cell cultures exposed to 2 Gy X-ray radiation (irradiated cell conditioned medium: ICCM). We only observed increased MN prevalence and induction of DNA damage foci in A603-1 and A603-3 cells after ICCM transfer. The ICCM of A603-3 (RIBE-induced) was able to induce MN in A603-4 (not RIBE-induced). To assess the possible contribution of reactive oxygen species (ROS) or nitric oxide (NO) in medium-mediated RIBE, dimethyl sulfoxide (DMSO; a ROS scavenger) or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO; an NO scavenger) were added to the medium. A suppressive effect was observed after adding DMSO, but there was no effect after treatment with c-PTIO. These results suggest that an enhanced radiosensitivity may not be directly related to the induction of medium-mediated RIBE. Moreover, ROS are involved in the transduction of the RIBE signal in A. speciosus cells, but NO is not. In conclusion, our results suggest that RIBE may be conserved in wild animals. The results contribute to better knowledge of radiation effects on wild, non-human species.
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Affiliation(s)
- Kentaro Ariyoshi
- Department of Radiation Biology, Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, 036-8564, Japan.
| | - Tomisato Miura
- Department of Biomedical Sciences, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, 036-8564, Japan
| | - Kosuke Kasai
- Department of Biomedical Sciences, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, 036-8564, Japan
| | - Nakata Akifumi
- Department of Basic Pharmacy, Hokkaido Pharmaceutical University School of Pharmacy, 7-1 Katsuraoka-cho, Otaru, Hokkaido, 047-0264, Japan
| | - Yohei Fujishima
- Department of Biomedical Sciences, Hirosaki University Graduate School of Health Sciences, 66-1 Hon-cho, Hirosaki, 036-8564, Japan
| | - Mitsuaki A Yoshida
- Department of Radiation Biology, Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, 036-8564, Japan.
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Abstract
AbstractMaize is one of model plants useful for genetic investigations and also very important for its agrotechnical utilizations. Here the genotoxic effects of low dose X-rays and accelerated electrons in maize caryopses was carried out with focus on the influence of water content at the moment of seed irradiation. X-ray photon beam as well as accelerated electrons were provided with 2.40 Gy min−1 dose rate. Pre-soaked and dry maize caryopses were irradiated with 0.5–3.0–6.0 Gy. Cytogenetic investigations were carried out based on microscope observations of chromosomes stained by Feulgen method. The mitotic index was found diminished in hydrated samples indicating the negative influence of indirect effects of water radicals. As known the water radiolysis release free radicals that attack biomolecules in addition to the directly absorbed radiation impact. Slight positive influence of 0.5 Gy radiation dose on cell division was evidenced. Chromosomal aberrations were identified like: vagrand chromosomes, C-metaphases, picnotic chromosomes, chromatide bridges. General tendency of aberrant mitoses enhancing was recorded in watered samples — with up to the twice increase for 6.0 Gy radiation dose. The results evidenced the hydration role in monitoring cytogenetic effects of low dose radiations in plant systems -with possible biotechnological applications.
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Choi VWY, Yu KN. Embryos of the zebrafish Danio rerio in studies of non-targeted effects of ionizing radiation. Cancer Lett 2013; 356:91-104. [PMID: 24176822 DOI: 10.1016/j.canlet.2013.10.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 10/16/2013] [Accepted: 10/22/2013] [Indexed: 01/17/2023]
Abstract
The use of embryos of the zebrafish Danio rerio as an in vivo tumor model for studying non-targeted effects of ionizing radiation was reviewed. The zebrafish embryo is an animal model, which enables convenient studies on non-targeted effects of both high-linear-energy-transfer (LET) and low-LET radiation by making use of both broad-beam and microbeam radiation. Zebrafish is also a convenient embryo model for studying radiobiological effects of ionizing radiation on tumors. The embryonic origin of tumors has been gaining ground in the past decades, and efforts to fight cancer from the perspective of developmental biology are underway. Evidence for the involvement of radiation-induced genomic instability (RIGI) and the radiation-induced bystander effect (RIBE) in zebrafish embryos were subsequently given. The results of RIGI were obtained for the irradiation of all two-cell stage cells, as well as 1.5 hpf zebrafish embryos by microbeam protons and broad-beam alpha particles, respectively. In contrast, the RIBE was observed through the radioadaptive response (RAR), which was developed against a subsequent challenging dose that was applied at 10 hpf when <0.2% and <0.3% of the cells of 5 hpf zebrafish embryos were exposed to a priming dose, which was provided by microbeam protons and broad-beam alpha particles, respectively. Finally, a perspective on the field, the need for future studies and the significance of such studies were discussed.
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Affiliation(s)
- V W Y Choi
- Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong
| | - K N Yu
- Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong; State Key Laboratory in Marine Pollution, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong.
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Li F, Wang T, Xu S, Yuan H, Bian P, Wu Y, Wu L, Yu Z. Abscopal mutagenic effect of low-energy-ions inArabidopsis Thalianaseeds. Int J Radiat Biol 2011; 87:984-92. [DOI: 10.3109/09553002.2011.574780] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Yu H, Zhao J, Xu J, Li X, Zhang F, Wang Y, Carr C, Zhang J, Zhang G. Detection of Changes in DNA Methylation Induced by Low-Energy Ion Implantation in Arabidopsis thaliana. Radiat Res 2011; 175:599-609. [DOI: 10.1667/rr2209.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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De Micco V, Arena C, Pignalosa D, Durante M. Effects of sparsely and densely ionizing radiation on plants. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2011; 50:1-19. [PMID: 21113610 DOI: 10.1007/s00411-010-0343-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 11/05/2010] [Indexed: 05/09/2023]
Abstract
One of the main purposes leading botanists to investigate the effects of ionizing radiations is to understand plant behaviour in space, where vegetal systems play an important role for nourishment, psychological support and functioning of life support systems. Ground-based experiments have been performed with particles of different charge and energy. Samples exposed to X- or γ-rays are often used as reference to derive the biological efficiency of different radiation qualities. Studies where biological samples are exposed directly to the space radiation environment have also been performed. The comparison of different studies has clarified how the effects observed after exposure are deeply influenced by several factors, some related to plant characteristics (e.g. species, cultivar, stage of development, tissue architecture and genome organization) and some related to radiation features (e.g. quality, dose, duration of exposure). In this review, we report main results from studies on the effect of ionizing radiations, including cosmic rays, on plants, focusing on genetic alterations, modifications of growth and reproduction and changes in biochemical pathways especially photosynthetic behaviour. Most of the data confirm what is known from animal studies: densely ionizing radiations are more efficient in inducing damages at several different levels, in comparison with sparsely ionizing radiation.
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Affiliation(s)
- Veronica De Micco
- Dipartimento di Arboricoltura, Botanica e Patologia Vegetale, Università degli Studi di Napoli Federico II, via Università 100, 80055, Portici (Naples), Italy
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Mei T, Yang G, Quan Y, Wang W, Zhang W, Xue J, Wu L, Gu H, Schettino G, Wang Y. Oxidative metabolism involved in non-targeted effects induced by proton radiation in intact Arabidopsis seeds. JOURNAL OF RADIATION RESEARCH 2011; 52:159-167. [PMID: 21343677 DOI: 10.1269/jrr.10087] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Non-targeted effects induced by ionizing radiation have been demonstrated both in vitro and in vivo. Previously, we have also demonstrated the existence of non-targeted effects in intact Arabidopsis seeds following low-energy heavy-ion radiation. In the present study, 6.5 MeV protons with 8 × 10(11) ions/cm(2) and 2 × 10(11) ions/cm(2) fluence respectively were used to irradiate non-shielded or partial-shielded Arabidopsis seeds to further explore the mechanisms which regulate in vivo non-targeted effects and to investigate the difference between damage caused by non-targeted effects and direct irradiation. Results showed that excess reactive oxygen species (ROS) are present in the non-irradiated part of the partially irradiated samples, indicating that in vivo non-targeted effects can promote the generation of excess metabolic ROS in the non-irradiated shoot apical meristem/root apical meristem cells. Furthermore, pretreatment with 0.5% ROS scavenger dimethyl sulfoxide (DMSO) or 0.02 mM reactive nitrogen species (RNS) scavenger 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) significantly suppresses the non-targeted effects in the partially irradiated samples, while in the whole-body irradiated samples, the cPTIO pretreatment has no effect. On the other hand using antioxidant enzyme assays, superoxide dismutase activity was found to increase for partial irradiated samples and decrease for the whole-body exposed seeds. Taken together, these results implicate that damage caused by non-targeted effects is different from that induced by direct irradiation in vivo. Metabolic products such as ROS and RNS are involved in the in vivo non-targeted effects.
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Affiliation(s)
- Tao Mei
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, People’s Republic of China
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Shi JM, Guo JG, Li WJ, Zhang M, Huang L, Sun YQ. Cytogenetic effects of low doses of energetic carbon ions on rice after exposures of dry seeds, wet seeds and seedlings. JOURNAL OF RADIATION RESEARCH 2010; 51:235-242. [PMID: 20505262 DOI: 10.1269/jrr.09085] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In order to investigate the biological effects of heavy ion radiation at low doses and the different radiosensitivities of growing and non-growing plants, rice at different lift stages (dry seed, wet seed and seedling) were exposed to carbon ions at doses of 0.02, 0.2, 2 and 20 Gy. Radiobiological effects on survival, root growth and mitotic activity, as well as the induction of chromosome aberrations in root meristem, were observed. The results show that radiation exposure induces a stimulatory response at lower dose and an inhibitory response at higher dose on the mitotic activity of wet seeds and seedlings. Cytogenetic damages are induced in both seeds and seedlings by carbon ion radiation at doses as low as 0.02 Gy. Compared with seedlings, seeds are more resistant to the lethal damage and the growth rate damage by high doses of carbon ions, but are more sensitive to cytogenetic damage by low doses of irradiation. Different types of radiation induced chromosome aberrations are observed between seeds and seedlings. Based on these results, the relationships between low dose heavy ion-induced biological effects and the biological materials are discussed.
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Affiliation(s)
- Jin-Ming Shi
- Department of Life Science and Engineering, Harbin Institute of Technology, Harbin, China
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Li K, Jiang S, Yu H, Zhao J, Zhang F, Carr C, Zhang J, Zhang G. Analysis of charge and mass effects on peroxidase expressions and activities in Arabidopsis thaliana after low-energy ion irradiation. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2009; 680:64-9. [DOI: 10.1016/j.mrgentox.2009.09.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 08/20/2009] [Accepted: 09/26/2009] [Indexed: 01/07/2023]
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Yang G, Mei T, Yuan H, Zhang W, Chen L, Xue J, Wu L, Wang Y. Bystander/abscopal effects induced in intact Arabidopsis seeds by low-energy heavy-ion radiation. Radiat Res 2008; 170:372-80. [PMID: 18763864 DOI: 10.1667/rr1324.1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 03/02/2008] [Indexed: 11/03/2022]
Abstract
To date, radiation-induced bystander effects have been observed largely in in vitro single-cell systems; verification of both the effects and the mechanisms in multicellular systems in vivo is important. Previously we showed that bystander/ abscopal effects can be induced by irradiating the shoot apical meristem cells in Arabidopsis embryos. In this study, we investigated the in vivo effects induced by 30 keV 40Ar ions in intact Arabidopsis seeds and traced the postembryonic development of both irradiated and nonirradiated shoot apical meristem and root apical meristem cells. Since the range of 30 keV 40Ar ions in water is about 0.07 microm, which is less than the distance from the testa to shoot apical meristem and root apical meristem in Arabidopsis seeds (about 100 microm), the incident low-energy heavy ions generally stop in the proximal surface. Our results showed that, after the 30 keV 40Ar-ion irradiation of shielded and nonshielded Arabidopsis seeds at a fluence of 1.5 x 10(17) ions/cm2, short- and long-term postembryonic development, including germination, root hair differentiation, primary root elongation, lateral root initiation and survival, was significantly inhibited. Since shoot apical meristem and root apical meristem cells were not damaged directly by radiation, the results suggested that a damage signal(s) is transferred from the irradiated cells to shoot apical meristem and root apical meristem cells and causes the ultimate developmental alterations, indicating that long-distance bystander/ abscopal effects exist in the intact seed. A further study of mechanisms showed that the effects are associated with either enhanced generation of reactive oxygen species (ROS) or decreased auxin-dependent transcription in postembryonic development. Treatment with the ROS scavenger dimethyl sulfoxide (DMSO) or synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) can significantly reverse both the alterations in postembryonic development and auxin-dependent transcription, suggesting that ROS and auxin-dependent transcription processes play essential roles in the low-energy heavy-ion radiation-induced long-distance bystander/abscopal effects in the intact organism.
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Affiliation(s)
- Gen Yang
- State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, People's Republic of China
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