Comparative Analysis of Arabidopsis Ecotypes Reveals a Role for Brassinosteroids in Root Hydrotropism
Comparative Analysis of Arabidopsis Ecotypes Reveals a Role for Brassinosteroids in Root Hydrotropism
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拟南芥生态型的比较分析揭示了油菜素类固醇在根向水性中的作用
DOI：
10.1104/pp.17.01563
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发表时间：
2018-04-01
期刊：
影响因子：
7.4
通讯作者：
Xu, Weifeng
中科院分区：
文献类型：
--
作者：
Miao, Rui;Wang, Meng;Xu, Weifeng
植物根部对土壤湿度梯度做出反应，并通过向水性改变其对水的生长方向，这是适应不断变化的土壤环境的重要过程。然而，根部水溶响应的机制仍然知之甚少。在这里，我们研究了从世界不同地区收集并在专门设计的土壤模拟系统中沿着湿度梯度生长的 31 种拟南芥 (Arabidopsis thaliana) 生态型的向水性。对三种选定的生态型 Wassilewskija (Ws)、Columbia (Col-0)（强亲水性）、Col-0（中度亲水性）和 C24（弱亲水性）以及具有改变的根亲水性反应的突变系进行了比较转录组分析和生理分析。我们发现 H+ 流出、Ca2+ 流入、氧化还原稳态、表观遗传调控和植物激素信号传导可能有助于根向水性。在植物激素中，油菜素类固醇（BR）的作用得到了进一步研究。在存在 BR 生物合成抑制剂的情况下，在 Ws 中观察到的强水溶响应会减弱。与表现出弱水溶响应的生态型 C24 相比，根 H+ 流出和初生根伸长也受到抑制。与野生型 Ws 相比，BR 不敏感突变体 bri1-5 在垂直或倾斜方向的水分梯度上表现出更高的根生长抑制率和根曲率。我们还证明了 BRI1（一种 BR 受体）与 AHA2（一种质膜 H+-ATP 酶）相互作用，并且它们的表达模式高度协调。这种协同作用可能有助于在 Ws 中观察到的强向水性。我们的结果表明，BR 相关的 H+ 外流对于拟南芥根的水溶响应至关重要。
Plant roots respond to soil moisture gradients and remodel their growth orientation toward water through hydrotropism, a process vital for acclimation to a changing soil environment. Mechanisms underlying the root hydrotropic response, however, remain poorly understood. Here, we examined hydrotropism in 31 Arabidopsis (Arabidopsis thaliana) ecotypes collected from different parts of the world and grown along moisture gradients in a specially designed soil-simulation system. Comparative transcriptome profiling and physiological analyses were carried out on three selected ecotypes, Wassilewskija (Ws), Columbia (Col-0) (strongly hydrotropic), Col-0 (moderately hydrotropic), and C24 (weakly hydrotropic), and in mutant lines with altered root hydrotropic responses. We show that H+ efflux, Ca2+ influx, redox homeostasis, epigenetic regulation, and phytohormone signaling may contribute to root hydrotropism. Among phytohormones, the role of brassinosteroids (BRs) was examined further. In the presence of an inhibitor of BR biosynthesis, the strong hydrotropic response observed in Ws was reduced. The root H+ efflux and primary root elongation also were inhibited when compared with C24, an ecotype that showed a weak hydrotropic response. The BR-insensitive mutant bri1-5 displayed higher rates of root growth inhibition and root curvature on moisture gradients in vertical or oblique orientation when compared with wild-type Ws. We also demonstrate that BRI1 (a BR receptor) interacts with AHA2 (a plasma membrane H+-ATPase) and that their expression patterns are highly coordinated. This synergistic action may contribute to the strong hydrotropism observed in Ws. Our results suggest that BR-associated H+ efflux is critical in the hydrotropic response of Arabidopsis roots.