Untargeted metabolomics of grapevine apoplastic fluid

The metabolome from the apoplastic fluid (APF) of grapevine cultivars 'Trincadeira' and 'Regent' was analysed by Fourier Transform Ion Cyclotron Resonance mass spectrometry (FT-ICR-MS). For the analysis, the extracted APF was diluted 1000-fold in methanol and human leucine enkephalin (Sigma Aldrich) was added for internal online calibration ([M+H]+ =556.276575 Da or [M-H]- = 554.262022 Da). Samples were analysed by direct infusion on a 7-Tesla SolariX XR FT-ICR-MS equipped with the ParaCell (Brüker Daltonics). Spectra were acquired with an accumulation of 200 scans, at positive (ESI+) and negative (ESI-) electrospray ionization modes, in the mass range of 100 to 1000 m/z. Data Analysis software (Brüker Daltonics) was used to generate the peak lists (m/z and intensity), considering a minimum signal-to-noise ratio of 4. The five replicates were aligned at 1 ppm.