Submitted to: Fungal Genetics and Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/2/2013
Publication Date: 6/7/2013
Citation: Boudreau, B.A., Larson, T.M., Brown, D.W., Busman, M., Roberts, E.S., Kendra, D.F., McQuade, K.L. 2013. Impact of temperature stress and validamycin A on compatible solutes and fumonisin production in F. verticillioides: Role of trehalose-6-phosphate synthase. Fungal Genetics and Biology. 57:1-10. Interpretive Summary: Fusarium verticillioides is a fungus that causes disease in corn that can result in contamination of corn and corn products with a number of fungal toxins (mycotoxins) including fumonisins. The characterization of the fungal response to stress from changes in environmental factors during growth could provide new targets to limit fungal growth and toxin contamination. One common fungal response to stress is to accumulate small molecules, such as trehalose, a disaccharide of glucose, that help protect against changes in water levels. In the current study, we examined the affect of heat or cold stress or treatment with validamycin A, an inhibitor of trehalose synthesis, on accumulation of compatible solutes and fumonisin production. We also examined the role of the gene encoding trehalose-6-phosphate synthase in trehalose synthesis. Genetic mutant strains were unable to synthesize trehalose, displayed altered growth characteristics, were reduced in their ability to cause disease of maize, and produced negligible fumonisin, suggesting an interplay between the trehalose and fumonisin metabolic pathways and pathogenicity. This research is critical to assessing the role of environmental stresses in plant disease, and will be of use to plant pathologists, plant breeders, and other scientists focused on the development of novel strategies to limit or control toxin contamination of grain in order to keep our food supply safe.
Technical Abstract: Fusarium verticillioides is a pathogen of maize that causes root, stalk, and ear rot and produces fumonisins, toxic secondary metabolites associated with disease in livestock and humans. Environmental stresses such as heat and drought influence disease severity and toxin production, but the effects of abiotic stress on compatible solute production by F. verticillioides have not been fully characterized. We found that trehalose levels increased rapidly in response to heat stress and decreased rapidly in response to cold stress. The effects of temperature stress on polyols were opposite those on trehalose, although less dramatic. Treatment with the trehalose analog validamycin A led to rapid loss of trehalose, which was unexpected given its role as an inhibitor of trehalases. Mutant strains lacking TPS1, encoding a putative trehalose-6-phosphate synthase, had altered growth characteristics, did not produce detectable amounts of trehalose under any condition tested, and accumulated glycogen at levels significantly higher than wild-type F. verticillioides. Surprisingly, TPS1 mutants also produced significantly less fumonisin and were less pathogenic than wild type on maize. These data point to possible links between trehalose biosynthesis, secondary metabolism and disease, and suggest that trehalose metabolic pathways may be a viable target for the control of Fusarium diseases and fumonisin contamination of maize.