期刊：Plant Cell & Environment
标题：Herbivore exposure alters ion fluxes and improves salt tolerance in a desert shrub
Plants have evolved complex mechanisms that allow them to withstand multiple environmental stresses, including biotic and abiotic stresses.
Here, we investigated the interaction between herbivore exposure and salt stress of Ammopiptanthus nanus, a desert shrub. We found that jasmonic acid (JA) was involved in plant responses to both herbivore attack and salt stress, leading to an increased NaCl stress tolerance for herbivore-pretreated plants, and increase in K+/Na+ ratio in roots. Further evidence revealed the mechanism by which herbivore improved plant NaCl tolerance. Herbivore pretreatment reduced K+ efflux and increased Na+ efflux in plants subjected to long-term, short-term, or transient NaCl stress.
Moreover, herbivore pretreatment promoted H+ efflux by increasing plasma membrane H+-ATPase activity. This H+ efflux creates a transmembrane proton motive force that drives the Na+/H+ antiporter to expel excess Na+ into the external medium. In addition, high cytosolic Ca2+ was observed in the roots of herbivore-treated plants exposed to NaCl, and this effect may be regulated by H+-ATPase.
Taken together, herbivore exposure enhances A. nanus tolerance to salt stress by activating the JA signalling pathway, increasing plasma membrane H+-ATPase activity, promoting cytosolic Ca2+ accumulation, and then restricting K+ leakage and reducing Na+ accumulation in the cytosol.
在这里，我们调查了草食动物暴露与沙漠灌木沙冬青盐胁迫之间的相互作用。我们发现茉莉酸（JA）参与了植物对食草动物侵袭和盐胁迫的反应，导致食草动物预处理过的植物对NaCl胁迫的耐受性增加，并且根中K+ / Na+比率增加。进一步的证据揭示了草食动物改善植物NaCl耐受性的机制。草食动物预处理可降低长期，短期或短暂NaCl胁迫下植物的K+流出量并增加Na +流出量。
此外，草食动物预处理通过增加质膜H+ -ATPase活性来促进H +流出。这种H+外流产生跨膜质子原动力，该原动力驱动Na+ / H+反向转运蛋白将过量的Na+排出到外部介质中。此外，在暴露于NaCl的食草动物处理过的植物的根部中观察到高的胞质Ca2+，这种作用可能受H+ -ATPase调节。
总之，通过激活JA信号传导途径，增加质膜H+ -ATPase活性，促进胞质Ca2 +积累，然后限制K+泄漏并减少细胞质中Na +的积累，草食动物暴露增强了南芥对盐胁迫的耐受性。
Figure 2. Effects of NaCl on the stable and transient flux of K+ along the A. nanus root axis (from 0 to 2000 μm from the root apex) with or without herbivore pretreatment. (A) The stable K+ flux was recorded along the axis of the root apex (0~2000 μm from the root tip) at 200-μm intervals, after long-term (LT) combined stresses (24-h HE + 7-d NaCl), salt stress (7-d NaCl), or no stress (control). (B) The bar chart represents the mean K+ flux value of all points along the roots following the four treatments. (C) The transient K+ flux kinetics were measured at the surface of the root, 600 μm from the tip, before and after the application of 100 mM NaCl. Three minutes of baseline data were recorded before NaCl application. The arrow indicates the time point of NaCl addition. Ten minutes of data were recorded after NaCl application. Samples were pretreated with tetraethylammonium (TEA), a K+ channel blocker, for 30 min before test. (D) The mean K+ flux was calculated before (pre-exposure), immediately after (peak-response), and 10 min after (post-exposure) the NaCl treatment. Different letters indicate significant differences at P ≤ 0.05 (Student’s t-test). Data were obtained from 5–7 A. nanus individuals. Error bars represent SE.