Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2006
Publication Date: 7/18/2006
Citation: Johnson, E.G., Wach, M., Gibson, D.M., Loria, R. 2006. Thaxtomin biosynthesis in plant-pathogenic streptomyces is induced by cellobiose, a plant cell wall component [abstract]. American Phytopathological Society Annual Meeting. 96:555. Interpretive Summary:
Technical Abstract: Common scab of potato is caused by multiple phylogenetically distinct Streptomyces spp. that are also capable of infecting underground parts of many other plant species. All scab-causing streptomycetes produce the necrogenic phytotoxin thaxtomin. Thaxtomin inhibits cellulose biosynthesis in expanding plant tissue by an unknown mechanism. However, pathogenic streptomycetes only produce thaxtomin in plant-based media, suggesting that one or more plant-derived compounds induce thaxtomin biosynthesis. Knowledge of the inducer could be helpful in combating the disease. Previously, we have shown that the recognition event driving thaxtomin production involves cell wall components. By testing cell wall polymer-derived disaccharides, we have identified cellobiose, the smallest subunit of cellulose, as the only disaccharide capable of inducing thaxtomin. Plant-pathogenic Streptomyces are unable to degrade or utilize intact cellulose, but do utilize cellobiose. This suggests a model where thaxtomin inhibition of cellulose biosynthesis releases cellobiose as an easily accessible carbon source, creating a positive feedback loop for thaxtomin biosynthesis.