Table_1_Foliar Application of Silicon Enhances Resistance Against Phytophthora infestans Through the ET/JA- and NPR1- Dependent Signaling Pathways in Potato.doc

Late blight (LB), caused by the oomycete pathogen Phytophthora infestans, is a devastating disease of potato that is necessary to control by regularly treatment with fungicides. Silicon (Si) has been used to enhance plant resistance against a broad range of bacterial and fungal pathogens; however, the enhanced LB resistance and the molecular mechanisms involving the plant hormone pathways remain unclear. In this study, Si treatment of potato plants was found to enhance LB resistance in both detached leaves and living plants accompanied by induction of reactive oxygen species (ROS) production and pathogenesis-related genes expression. Regarding the hormone pathways involved in Si-mediated LB resistance, we found a rapidly increased content of ethylene (ET) 15 min after spraying with Si. Increased jasmonic acid (JA) and JA-Ile and decreased salicylic acid (SA) were identified in plants at 1 day after spraying with Si and an additional 1 day after P. infestans EC1 infection. Furthermore, pretreatment with Me-JA enhanced resistance to EC1, while pretreatment with DIECA, an inhibitor of JA synthesis, enhanced the susceptibility and attenuated the Si-mediated resistance to LB. Consistent with these hormonal alterations, Si-mediated LB resistance was significantly attenuated in StETR1-, StEIN2-, StAOS-, StOPR3-, StNPR1-, and StHSP90-repressed plants but not in StCOI1- and StSID2-repressed plants using virus-induced gene silencing (VIGS). The Si-mediated accumulation of JA/JA-Ile was significantly attenuated in StETR1-, StEIN2-, StOPR3- and StHSP90-VIGS plants but not in StCOI1-, StSID2- and StNPR1-VIGS plants. Overall, we reveal that Si can be used as a putative alternative to fungicides to control LB, and conclude that Si-mediated LB resistance is dependent on the ET/JA-signaling pathways in a StHSP90- and StNPR1-dependent manner.

由卵菌病原菌致病疫霉（Phytophthora infestans）引发的晚疫病（Late blight, LB）是马铃薯的毁灭性病害，生产中需通过定期喷施杀菌剂进行防控。硅（Silicon, Si）已被应用于增强植物对多种细菌和真菌病原菌的抗病性，但硅介导的晚疫病抗性及其涉及植物激素通路的分子机制仍未明确。本研究发现，对马铃薯植株施加硅处理后，可在离体叶片与活体植株中均提升晚疫病抗性，同时诱导活性氧（reactive oxygen species, ROS）的产生与病程相关基因（pathogenesis-related genes）的表达。针对硅介导晚疫病抗性所涉及的激素通路，研究发现喷施硅后15分钟，乙烯（ethylene, ET）的含量快速升高；在喷施硅后1天以及致病疫霉EC1接种后1天的植株中，可检测到茉莉酸（jasmonic acid, JA）及其结合物茉莉酸-异亮氨酸结合物（JA-Ile）的含量上升，而水杨酸（salicylic acid, SA）的含量则出现下降。此外，提前施用茉莉酸甲酯（Me-JA）可增强植株对EC1的抗性；而提前施加茉莉酸合成抑制剂二乙基二硫代氨基甲酸酯（DIECA）则会加重植株的感病性，并削弱硅介导的晚疫病抗性。通过病毒诱导基因沉默（virus-induced gene silencing, VIGS）抑制StETR1、StEIN2、StAOS、StOPR3、StNPR1及StHSP90的表达后，硅介导的晚疫病抗性显著减弱；而抑制StCOI1与StSID2的表达则未出现该现象。在StETR1、StEIN2、StOPR3及StHSP90沉默植株中，硅介导的JA/JA-Ile积累显著受到抑制，但在StCOI1、StSID2及StNPR1沉默植株中未观察到此效应。综上，本研究揭示硅可作为潜在的杀菌剂替代品用于晚疫病防控，并证实硅介导的晚疫病抗性依赖于乙烯/茉莉酸信号通路，且该过程依赖StHSP90与StNPR1基因。