<i>In\nVivo</i> and Real-Time Metabolic Profiling\nof Plant–Microbe Interactions in Leaves, Stems, and Roots of\nBacterially Inoculated Chardonnay Plantlets using SpiderMass

There is growing interest in limiting the use of fungicides\nand\nimplementing innovative, environmentally friendly strategies, such\nas the use of beneficial bacteria-triggered immunity, to protect grapevines\nfrom natural pathogens. Therefore, we need rapid and innovative ways\nto translate the knowledge of the molecular mechanisms underlying\nthe activation of grapevine defenses against pathogens to induced\nresistance. Here, we have implemented an <i>in vivo</i> minimally\ninvasive approach to study the interaction between plants and beneficial\nbacteria based on metabolic signatures. <i>Paraburkholderia phytofirmans</i> strain PsJN and PsJN–grapevine were used as bacterial and\nplant–bacterium interaction models, respectively. Using an\ninnovative tool, SpiderMass, based on water-assisted laser desorption\nionization with an IR microsampling probe, we simultaneously detect\nmetabolic and lipidomic species. A metabolomic spectrum was thus generated,\nwhich was used to build a library and identify the most variable and\ndiscriminative peaks between the two conditions. We then showed that\ncaftaric acid (<i>m</i>/<i>z</i> 311.04), caftaric\nacid dimer (<i>m</i>/<i>z</i> 623.09), derived\ncaftaric acid (<i>m</i>/<i>z</i> 653.15), and\nquercetin-<i>O</i>-glucuronide tended to accumulate in grapevine\nleaves after root bacterization with PsJN. In addition, together with\nthese phenolic messengers, we identified lipid biomarkers such as\npalmitic acid, linoleic acid, and α-linoleic acid as important\nmessengers of enhanced defense mechanisms in Chardonnay plantlets.\nTaken together, SpiderMass is the next-generation methodology for\nstudying plant–microorganism metabolic interactions with the\nprospect of <i>in vivo</i> real-time analysis in viticulture.