褪黑素调节烟草丁香假单胞菌抗性的功能研究

为分析褪黑素(N-乙酰-5-甲氧基色胺)在植物先天免疫中的功能及调控机理,研究以病原菌丁香假单胞杆菌(Pseudomonas syringae pv.tomato DC3000,Pst DC3000)—烟草互作系统为模型,检测了病原菌侵染对烟草褪黑素相关基因表达的影响,并探讨了褪黑素对植物叶片病原菌生长以及气孔开度和活性氧自由基(reactive oxygen species,ROS)含量的影响以及调控机理。结果表明:(1)Pst DC3000处理提高了烟草褪黑素合成(NtSNAT1)和受体(NtPMTR1)基因表达,且外源褪黑素处理降低了叶片中的病原菌含量。(2)与野生型植物相比,过表达大豆GmSNAT1基因显著提高了转基因烟草中内源褪黑素含量和NtPMTR1的表达,且转基因烟草叶片中的Pst DC3000菌落数显著下降。(3)外源褪黑素和细菌鞭毛蛋白多肽flg22处理诱导了野生型和转基因烟草保卫细胞中ROS产生和气孔关闭,且转基因植物对褪黑素和flg22诱导的气孔关闭和ROS产生比野生型烟草更加敏感。综上所述,研究表明褪黑素可能通过受体NtPMTR1介导的信号途径促进保卫细胞ROS产生,诱导气孔关闭,从而降低病原菌Pst DC3000的入侵。

Functional Analysis of Melatonin in the Regulation of Tobacco Plants Resistance to Pseudomonas syringae

Melatonin (N-acetyl-5-methoxytryptamine, MT) is a pervasive signaling molecule in organisms and plays an important role in plant pathogen resistance. In order to understand the function of melatonin in plant immunity, the regulatory mechanism of melatonin in tobacco immunity was analyzed using Pseudomonas syringae pv.tomato DC3000 (Pst DC3000). The results showed that Pst DC3000 treatment increased the melatonin synthesis (NtSNAT1) and potential receptor (NtPMTR1) genes expression in tobacco, and exogenous phytomelatonin reduced the content of pathogenic bacteria in leaves. Overexpression of soybean GmSNAT1 significantly increased the endogenous melatonin concentrations and the expression of NtPMTR1 in GMSNAT1-OE2 and GMSNAT1-OE5, and the resistance of the transgenic plants to pathogen Pst DC3000 also significantly increased. Exogenous melatonin and flg22 treatments induced ROS production and stomatal closure in wild-type and transgenic tobacco guard cells, and transgenic plants were more sensitive to melatonin and flg22-induced stomatal closure and ROS production than wild-type tobacco. This study found that melatonin can significantly improve plants resistance to Pst DC3000, which may promote ROS production in guard cells and induce stomatal closure through the signaling pathway mediated by receptor NtPMTR1 to reduce the invasion of pathogens.