Reactive Oxygen Species Tune Root Tropic Responses
Reactive Oxygen Species Tune Root Tropic Responses
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DOI：
10.1104/pp.16.00660
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发表时间：
2016-10-01
期刊：
影响因子：
7.4
通讯作者：
Fromm, Hillel
中科院分区：
文献类型：
--
作者：
Krieger, Gat;Shkolnik, Doron;Fromm, Hillel
陆地植物初生根的默认生长模式是由重力引导的。然而，根具有单独或组合地感知和定向响应其他化学和物理刺激的能力。因此，这些根向性反应必定与向地性相反。活性氧（ROS）在玉米和拟南芥（Arabidopsis thaliana）根的向地性中的作用已被描述过。然而，目前尚不清楚哪些细胞信号是不同环境刺激整合的基础，从而导致适当的根向性反应。在重力响应根中，我们通过应用 ROS 敏感荧光染料二氢罗丹明-123 和共聚焦显微镜观察到短暂的不对称 ROS 分布，在根的凹侧较高。在远端伸长区检测到的不对称性是在重力响应的前 2 小时内建立的，并在另外 2 小时后消散。相比之下，亲水响应的根部没有表现出短暂的活性氧不对称分布。通过使用抗氧化剂抗坏血酸盐或 ROS 生成抑制剂二亚苯基碘来降低 ROS 水平，可以减弱向地性，同时增强向水性。抗坏血酸过氧化物酶 1 缺陷的拟南芥突变体表现出水溶根弯曲减弱。根部表达的 NADPH 氧化酶 RBOH C 突变体（但不是 rbohD）表现出增强的向水性和根尖中较少的 ROS（在使用 Amplex Red 的组织提取物中进行测试）。最后，重力刺激之前的水刺激减弱了重力刺激的不对称ROS和生长素信号，这是重力定向曲率所需的。我们认为，ROS（大概是 H2O2）通过促进向地性和负调节向水性来调节根向性反应。
The default growth pattern of primary roots of land plants is directed by gravity. However, roots possess the ability to sense and respond directionally to other chemical and physical stimuli, separately and in combination. Therefore, these root tropic responses must be antagonistic to gravitropism. The role of reactive oxygen species (ROS) in gravitropism of maize and Arabidopsis (Arabidopsis thaliana) roots has been previously described. However, which cellular signals underlie the integration of the different environmental stimuli, which lead to an appropriate root tropic response, is currently unknown. In gravity-responding roots, we observed, by applying the ROS-sensitive fluorescent dye dihydrorhodamine-123 and confocal microscopy, a transient asymmetric ROS distribution, higher at the concave side of the root. The asymmetry, detected at the distal elongation zone, was built in the first 2 h of the gravitropic response and dissipated after another 2 h. In contrast, hydrotropically responding roots show no transient asymmetric distribution of ROS. Decreasing ROS levels by applying the antioxidant ascorbate, or the ROS-generation inhibitor diphenylene iodonium attenuated gravitropism while enhancing hydrotropism. Arabidopsis mutants deficient in Ascorbate Peroxidase 1 showed attenuated hydrotropic root bending. Mutants of the root-expressed NADPH oxidase RBOH C, but not rbohD, showed enhanced hydrotropism and less ROS in their roots apices (tested in tissue extracts with Amplex Red). Finally, hydrostimulation prior to gravistimulation attenuated the gravistimulated asymmetric ROS and auxin signals that are required for gravity-directed curvature. We suggest that ROS, presumably H2O2, function in tuning root tropic responses by promoting gravitropism and negatively regulating hydrotropism.