Tryptophol Improves the Biocontrol Efficacy of Scheffersomyces spartinae against the Gray Mold of Strawberries by Quorum Sensing

Previously, we reported that marine yeast Scheffersomyces spartinae exhibited biocontrol efficacy against the gray mold of strawberries caused by Botrytis cinerea. Herein, tryptophol, a quorum-sensing molecule, was identified in the metabolites of S. spartinae. Subsequently, we found that 25 μM tryptophol promoted population density, biofilm formation, and cell aggregation of S. spartinae. Furthermore, 25 μM tryptophol improved the biocontrol efficacy of S. spartinae against B. cinerea in vitro and in the strawberry fruit. Under a scanning electronic microscope, tryptophol facilitated colonization and biofilm formation on strawberry wounds, showing that tryptophol increased the biocontrol efficacy of S. spartinae via quorum sensing. Transcriptome analysis revealed that tryptophol upregulated the gene expression of SDS3, DAL81, DSE1, SNF5, SUN41, FLO8, and HOP1, which was associated with cell adhesion or biofilm formation. Thus, to the best of our knowledge, this study was the first to report that tryptophol improved the biocontrol efficacy of S. spartinae via quorum sensing.