Antifungal Mechanism of Biphenyl Phytoalexin Derivative Sorbauphylin A against Botrytis cinerea in Grapes

Botrytis cinerea causes
significant
losses in crops, especially in grapes. The biphenyl derivative sorbauphylin
A (4′-n-pentyl-[1,1′-biphenyl]-3,5-diol),
derived from plant phytoalexins, exerts potent antifungal effects
with low toxicity. This study demonstrated that sorbauphylin A significantly
inhibited the growth of B. cinerea (EC50 = 15 μg mL–1), suppressed spore
germination, and markedly reduced infection in grapes and leaves.
The results of fluorescence staining and enzyme activity detection
indicated that sorbauphylin A damaged cell membranes and walls and
triggered a reactive oxygen species burst. Transcriptome analysis
revealed that sorbauphylin A inhibited the thiamine biosynthesis pathway
by downregulating key genes Bcthi4 and Bcnmt1, which molecular docking confirmed, thereby reducing thiamine pyrophosphate
(TPP) production. This suppression of TPP disrupted pyruvate metabolism
and the tricarboxylic acid cycle, leading to mitochondrial energy
deficiency and consequently inducing oxidative stress and fungal cell
death. Sorbauphylin A represents a promising new fungicide for controlling
grape gray molds with broad application prospects.