Biotransformation of 4-hydroxybenzoic acid in the rhizosphere of grapevine (Vitis vinifera L.)

Although 4-hydroxybenzoic acid (4-HBA) is a model allelochemical for many plants, its biotransformation is still unexplored. Sixty grapevine (Vitis vinifera L.) rhizosphere soil samples (sterilized and non-sterilized) with 4-HBA (12C unlabeled or 13C labeled) were analyzed at 0, 0.5, 1, 2, 4, 6, 24, 50, and 68 h after incubation. Fourier transform ion cyclotron resonance mass spectrometry, combined with stable isotope probing technology data, showed that 4-HBA could be biotransformed into dimers, which was previously not known to occur, and that the allelopathic activity of 4-HBA might be maintained by depolymerization and dimer concentration. These dimers might be rapidly adsorbed or used by microbes and are a possible reason for grapevine soil autotoxicity. Hence, this study lays the foundation for future studies on phenolic acid allelochemicals, which will contribute to decipher the actively maintained allelopathy of grapevine soils and reduce its negative effects on grape and wine industries.