Secondary Metabolites of the Grapevine Pathogen Eutypa lata Inhibit Mitochondrial Respiration, Based on a Model Bioassay Using the Yeast Saccharomyces cerevisiae

Abstract

Acetylenic phenols and a chromene isolated from the grapevine fungal pathogen Eutypa lata were examined for mode of toxicity. The compounds included eutypine (4-hydroxy-3-[3-methyl-3-butene-1-ynyl] benzyl aldehyde), eutypinol (4-hydroxy-3-[3-methyl-3-butene-1-ynyl] benzyl alcohol), eulatachromene, 2-isoprenyl-5-formyl-benzofuran, siccayne, and eulatinol. A bioassay using the yeast Saccharomyces cerevisiae showed that all compounds were either lethal or inhibited growth. A respiratory assay using 2,3,5-triphenyltetrazolium (TTC) indicated that eutypinol and eulatachromene inhibited mitochondrial respiration in wild-type yeast. Bioassays also showed that 2-isoprenyl-5-formyl-benzofuran and siccayne inhibited mitochondrial respiration in the S. cerevisiae deletion mutant vph2Δ, lacking a vacuolar type H (+) ATPase (V-ATPase) assembly protein. Cell growth of tsa1Δ, a deletion mutant of S. cerevisiae lacking a thioredoxin peroxidase (cTPx I), was greatly reduced when grown on media containing eutypinol or eulatachromene and exposed to hydrogen peroxide (H₂O₂) as an oxidative stress. This reduction in growth establishes the toxic mode of action of these compounds through inhibition of mitochondrial respiration.