Submitted to: Current Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/23/2004
Publication Date: 8/1/2004
Citation: Kim, J.H., Mahoney, N.E., Chan, K.L., Molyneux, R.J., Campbell, B.C. Secondary metabolites of the grapevine pathogen eutypa lata inhibit mitochondrial respiration based on a model bioassay using the yeast saccharomyces cerevisiae. Current Microbiology. 2004. v.49. p.282-287. Interpretive Summary: 'Dying-arm disease' is a major disease of grape vines, worldwide. It is caused by a fungus that produces chemicals, called phytotoxins, that kill leaves and woody tissue of the vines. While the phytotoxins have been recently isolated and described, there is a need to know how these chemicals kill the plant. This paper uses some new methods that show how these chemicals may be killing the plant. The method involves the use of special types of yeasts that can help us identify what genes of the plant may be affected by the chemicals. From the use of these new methods, it is determined that the chemicals disrupt the ability of the plant to use a special cellular 'organelle' called a mitochondrion. Mitochondria help the plant produce energy, using oxygen and food. These chemicals make the mitochondrion so it cannot use the oxygen to make energy. Knowing how these chemicals work to make the plant sick may help us find a way to prevent the disease.
Technical Abstract: Six secondary metabolites, acetylenic phenols and a chromene isolated from the grapevine fungal pathogen Eutypa lata, were examined for mode of toxicity. The six 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 model bioassay system using various experimental strains of the yeast Saccharomyces cerevisiae showed all six compounds were either lethal or inhibited growth. A respiratory assay using an overlay of 2,3,5-triphenyltetrazolium (TTC) on culture media indicated eutypinol and eulatachromene inhibited mitochondrial respiration in wild-type yeast. This assay also showed that 2-isoprenyl-5-formyl-benzofuran and siccayne inhibited mitochondrial respiration in the S. cerevisiae deletion mutant vph2D, lacking a vacuolar type H (+) ATPase (V-ATPase) assembly protein. Cell growth of tsa1D, 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 confirmed the toxic mode of action of these compounds was through inhibition of mitochondrial respiration.