title: Targeted irradiation of shoot apical meristem of Arabidopsis embryos induces long-distance bystander/abscopal effects.
abstract: Bystander effects induced by low-dose ionizing radiation have been shown to occur widely in many cell types and may have a significant impact on radiation risk assessment. Although the region of radiation damage is known to be much greater than the initial target volume irradiated, it remains to be seen whether this response is limited to the specific organ irradiated, spans a limited region of the body, or even covers the whole body of the target. To determine whether long-distance bystander/abscopal effects exist in whole organisms and to clarify the problem of intercellular communication, in the present study a specific cell group, the shoot apical meristem in Arabidopsis embryo, was irradiated with a defined number of protons and examined for root development postirradiation. The results showed that after direct damage to the shoot apical meristem from ion traversals, root hair differentiation, primary root elongation and lateral root initiation were all inhibited significantly in postembryonic development, suggesting that radiation-induced long-distance bystander/abscopal responses might exist in the whole organism. To further scrutinize the mechanism(s) underlying these inhibitory effects, a DR5-GUS transgenic Arabidopsis was used. The results showed that accumulation of the reporter GUS gene transcript in irradiated shoot apical meristem embryos decreased in the postembryonic development. Treatment with either 2,4-dichlorophenoxyacetic acid, a synthetic plant auxin, or DMSO, a effective reactive oxygen species (ROS) scavenger, could rescue the reporter GUS enzyme accumulation and the length of primary root in irradiated shoot apical meristem embryos, indicating that ROS or probably the ROS related auxin and auxin-dependent transcription process may be involved in radiation-induced long-distance bystander/abscopal effects.
authors.affiliation: Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, People's Republic of China.
authors.forename: Gen
authors.initials: G
authors.lastname: Yang
authors.forename: Lijun
authors.initials: L
authors.lastname: Wu
authors.forename: Lianyun
authors.initials: L
authors.lastname: Chen
authors.forename: Bei
authors.initials: B
authors.lastname: Pei
authors.forename: Yugang
authors.initials: Y
authors.lastname: Wang
authors.forename: Furu
authors.initials: F
authors.lastname: Zhan
authors.forename: Yuejin
authors.initials: Y
authors.lastname: Wu
authors.forename: Zengliang
authors.initials: Z
authors.lastname: Yu
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000196:embryology* / Q000528:radiation effects*; D024201:Bystander Effect / Q000528:radiation effects*; D002454:Cell Differentiation; D018548:Cotyledon / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D007210:Indoleacetic Acids / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D018519:Meristem / Q000166:cytology / Q000187:drug effects / Q000196:embryology* / Q000528:radiation effects*; D030821:Plants, Genetically Modified; D011522:Protons; D017382:Reactive Oxygen Species / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects
chemical_list: D007210:Indoleacetic Acids; D011522:Protons; D017382:Reactive Oxygen Species; D005978:Glutathione; D004121:Dimethyl Sulfoxide