Yang Gen, Wu Lijun, Chen Lianyun, Pei Bei, Wang Yugang, Zhan Furu, Wu Yuejin, Yu Zengliang
Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, People's Republic of China.
Radiat Res. 2007 Mar;167(3):298-305. doi: 10.1667/RR0710.1.
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.
低剂量电离辐射诱导的旁观者效应已被证明在许多细胞类型中广泛存在，并且可能对辐射风险评估产生重大影响。尽管已知辐射损伤区域远大于最初照射的目标体积，但这种反应是否仅限于受照射的特定器官、跨越身体的有限区域，甚至覆盖目标的整个身体，仍有待观察。为了确定在整个生物体中是否存在远距离旁观者/远隔效应，并阐明细胞间通讯问题，在本研究中，用一定数量的质子照射拟南芥胚胎中的一个特定细胞群——茎尖分生组织，并在照射后检查根的发育情况。结果表明，离子穿过对茎尖分生组织造成直接损伤后，胚胎后期发育中的根毛分化、主根伸长和侧根起始均受到显著抑制，这表明在整个生物体中可能存在辐射诱导的远距离旁观者/远隔反应。为了进一步仔细研究这些抑制作用的潜在机制，使用了DR5-GUS转基因拟南芥。结果表明，在胚胎后期发育中，照射后的茎尖分生组织胚胎中报告基因GUS基因转录本的积累减少。用合成植物生长素2,4-二氯苯氧乙酸或有效的活性氧（ROS）清除剂二甲基亚砜处理，可以挽救照射后的茎尖分生组织胚胎中报告基因GUS酶的积累和主根长度，表明ROS或可能与ROS相关的生长素和生长素依赖性转录过程可能参与辐射诱导的远距离旁观者/远隔效应。
