Miura Kenji, Yamada Kosumi, Shigemori Hideyuki
Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, 305-8572, Japan,
Planta. 2014 Sep;240(3):513-24. doi: 10.1007/s00425-014-2103-5. Epub 2014 Jun 13.
Raphanusanin (Ra) is a light-induced inhibitor of hypocotyl growth that responds to unilateral blue light illumination in radish seedlings. We have previously shown that Ra regulates genes that are involved in common defense mechanisms. Many genes that are induced by Ra are also positively regulated by early blue light. To extend the understanding of the role of Ra in pathogen defense, we evaluated the effects of Ra on radish and Arabidopsis thaliana (A. thaliana) infected with the necrotrophic pathogen Botrytis cinerea (B. cinerea) and biotrophic pathogen Pseudomonas syringae (P. syringae). Radish and A. thaliana were found to be resistant to both pathogens when treated with Ra, depending on the concentration used. Interestingly, Ra-mediated resistance to P. syringae is dependent on light because Ra-treated seedlings exhibited enhanced susceptibility to P. syringae infection when grown in the dark. In addition to regulating the biotic defense response, Ra inhibited seed germination and root elongation and enhanced the growth of root hairs in the presence of light in radish and A. thaliana. Our data suggest that Ra regulates the expression of a set of genes involved in defense signaling pathways and plays a role in pathogen defense and plant development. Our results show that light may be generally required not only for the accumulation of Ra but also for its activation during the pathogen defense response.
莱菔宁（Ra）是一种光诱导的下胚轴生长抑制剂，对萝卜幼苗的单侧蓝光照射有反应。我们之前已经表明，Ra调控参与共同防御机制的基因。许多由Ra诱导的基因也受到早期蓝光的正向调控。为了进一步了解Ra在病原体防御中的作用，我们评估了Ra对感染了坏死性病原菌灰葡萄孢（B. cinerea）和活体营养型病原菌丁香假单胞菌（P. syringae）的萝卜和拟南芥的影响。发现用Ra处理时，萝卜和拟南芥对这两种病原菌均有抗性，这取决于所使用的浓度。有趣的是，Ra介导的对丁香假单胞菌的抗性依赖于光，因为在黑暗中生长时，经Ra处理的幼苗对丁香假单胞菌感染表现出更高的易感性。除了调节生物防御反应外，Ra还抑制种子萌发和根伸长，并在光照条件下促进萝卜和拟南芥根毛的生长。我们的数据表明，Ra调控一组参与防御信号通路的基因的表达，并在病原体防御和植物发育中发挥作用。我们的结果表明，光可能不仅是Ra积累所普遍需要的，而且在病原体防御反应中对其激活也是必需的。
