Nontargeted Metabolite Profiling in Compatible Pathogen-Inoculated Tobacco (Nicotiana tabacum L. cv. Wisconsin 38) Using UPLC-Q-TOF/MS

A biphasic reactive oxygen species (ROS) production has previously been observed in tobacco at 1 and 48 h after inoculation with the hemibiotrophic compatible pathogen, Phytophthora parasitica var. <i>nicotianae</i> (<i>Ppn</i>). To characterize the response of tobacco to biphasically produced ROS concerning the propagation of <i>Ppn</i>, ultraperformance liquid chromatography–quadrupole–time of flight/ mass spectrometry (UPLC-Q-TOF/MS) based metabolic profiling combined with multivariate statistical analysis was performed. Among the nonredundant 355 mass ions in ESI+ mode and 345 mass ions in ESI– mode that were selected as significantly changed by <i>Ppn</i> inoculation (|<i>p</i>(corr)| > 0.6 on S-plot of orthogonal partial least-squares discriminant analysis (OPLS-DA), fold-change > 2, and <i>p</i> < 0.05 in the independent two-sample <i>t</i> test), 76 mass ions were identified on the basis of their accurate mass ions and MS/MS spectra. Phenolic amino acids, phenylpropanoids, hydroxycinnamic acid amides, linoleic acid, linolenic acid, lysophospholipids, glycoglycerolipids, and trioxidized phospholipids were identified as having changed after <i>Ppn</i> inoculation. On the basis of their quantitative changes, the metabolic responses occurring at each phase of ROS production after <i>Ppn</i> inoculation were investigated in this study