Profiling and Localization of Stilbene Phytoalexins Revealed by MALDI-MSI during the Grapevine–Botrytis cinerea Interaction

Stilbene phytoalexins are among the most accumulated compounds during grapevine–pathogen interactions. However, their steady-state accumulation level and spatial distribution within the tissues to counteract Botrytis cinerea infection remain to be explored. In this work, matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) was used to determine the spatial distribution of different phytoalexins in grapevine leaves upon infection with B. cinerea. Ultraperformance liquid chromatography-fluorescence (UPLC-FL) was also employed to monitor the accumulation pattern of these phytoalexins. This study showed that stilbene compounds accumulate in areas close to the pathogen infection sites. It was also revealed that the accumulation patterns of the stilbene phytoalexins can vary from one time point postinfection to another with specific accumulation patterns within each time point. To the best of our knowledge, this is the first time that the separate localization of grapevine stilbene phytoalexins has been revealed following B. cinerea infection

¹³C NMR and LC-MS Profiling of Stilbenes from Elicited Grapevine Hairy Root Cultures

Resveratrol and related oligostilbenes are defense molecules produced by grapevine in response to stresses including various elicitors or signal molecules. Together with their prominent role <i>in planta,</i> these compounds have been the center of much attention in recent decades due to their pharmacological properties. The cost-effective production of resveratrol derivatives such as viniferins or more structurally complex stilbene oligomers remains a challenging task. In this study, the chemical diversity of stilbenes produced by <i>Vitis vinifera</i> Pinot Noir hairy roots was investigated after elicitation for 4 days with a mixture of methyl jasmonate (100 μM) and cyclodextrins (50 mM). Two crude extracts obtained from the culture medium and from the hairy roots were fractionated by centrifugal partition chromatography. The fractions were chemically investigated by two complementary identification approaches involving a ¹³C NMR-based dereplication method and liquid chromatography coupled to mass spectrometry (LC-MS). In total, groups of 21 and 18 molecules, including flavonoids and stilbenes, were detected in the culture medium and root extracts, respectively. These included resveratrol monomers, dimers, trimers, and a tetramer, thus highlighting the ability of elicited hairy root culture systems to synthesize a wide diversity of secondary metabolites of pharmaceutical significance. The main compounds were unambiguously identified as <i>trans</i>-resveratrol, ε-viniferin, <i>trans</i>-piceatannol, pallidol, scirpusin A, eriodictyol, naringenin, vitisin B, and maackin