Li Jisheng, Jia Honglei, Wang Jue
College of Life Sciences, Northwest A&F University, Yangling, 712100, Shaanxi, China,
Plant Cell Rep. 2014 Mar;33(3):447-59. doi: 10.1007/s00299-013-1545-8. Epub 2013 Dec 4.
cGMP promotes ethylene production and enhances the perception of ethylene. Endogenous ethylene or cGMP accumulation maintains ion homeostasis to enhancing salt resistance. etr1 - 3 is insensitive to cGMP under salt stress.
In the present study, we presented a signaling network involving ethylene and cGMP in salt resistance pathway of Arabidopsis roots. Results showed that the ethylene-insensitive mutant etr1-3 was more sensitive to salt stress than the wild type (WT). etr1-3 displayed a greater electrolyte leakage, thiobarbituric acid reactive substances and Na(+)/K(+) ratio, but a lower plasma membrane (PM) H(+)-ATPase activity compared to WT under the different NaCl contents. Application of 1-aminocyclopropane-1-carboxylic acid (ACC, an ethylene precursor) or 8-Br-cGMP (the cGMP analog) alleviated NaCl-induced injury by maintaining a lower Na(+)/K(+) ratio and increasing PM H(+)-ATPase activity in WT, but not in etr1-3. Roots treated with 8-Br-cGMP could promote ethylene production and enhance the expression of ACC synthase gene in WT. In addition, the 8-Br-cGMP action in NaCl stress was inhibited by aminooxyacetic acid (an inhibitor of ethylene biosynthesis), but 6-Anilino-5,8-quinolinedione (Ly83583, a guanylate cyclase inhibitor) could not affect ACC action in WT. These results suggest that ethylene functions as a downstream signal of cGMP that stimulates the PM H(+)-ATPase activity, which finally results in regulating ion homeostasis in Arabidopsis tolerance to salt. Moreover, cGMP enhanced the perception of ethylene in Arabidopsis under salt stress, which reversed the salt-induced increase of ETR1 and increased ERF1 at the transcript levels in WT. In a word, cGMP modulates salt resistance pathway of ethylene through regulating biosynthesis and perception of ethylene in Arabidopsis roots.
环磷酸鸟苷（cGMP）促进乙烯生成并增强对乙烯的感知。内源性乙烯或cGMP积累维持离子稳态以增强耐盐性。在盐胁迫下，乙烯受体1-3（etr1-3）对cGMP不敏感。
在本研究中，我们提出了一个在拟南芥根的耐盐途径中涉及乙烯和cGMP的信号网络。结果表明，乙烯不敏感突变体etr1-3比野生型（WT）对盐胁迫更敏感。在不同NaCl含量条件下，与WT相比，etr1-3表现出更大的电解质渗漏、硫代巴比妥酸反应性物质和Na(+)/K(+)比值，但质膜（PM）H(+) - ATP酶活性较低。施用1-氨基环丙烷-1-羧酸（ACC，一种乙烯前体）或8-溴-cGMP（cGMP类似物）通过维持较低的Na(+)/K(+)比值和增加WT中质膜H(+) - ATP酶活性来减轻NaCl诱导的损伤，但在etr1-3中则不然。用8-溴-cGMP处理的根可以促进WT中乙烯的生成并增强ACC合酶基因的表达。此外，氨基氧乙酸（一种乙烯生物合成抑制剂）抑制了8-溴-cGMP在NaCl胁迫中的作用，但鸟苷酸环化酶抑制剂6-苯胺基-5,8-喹啉二酮（Ly83583）不影响WT中ACC的作用。这些结果表明，乙烯作为cGMP的下游信号发挥作用，刺激质膜H(+) - ATP酶活性，最终导致调节拟南芥耐盐性中的离子稳态。此外，在盐胁迫下，cGMP增强了拟南芥对乙烯的感知，这在转录水平上逆转了盐诱导的乙烯受体1（ETR1）增加并增加了乙烯响应因子1（ERF1）在WT中的表达。总之，cGMP通过调节拟南芥根中乙烯的生物合成和感知来调节乙烯的耐盐途径。
