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Systemic Modulation of Gene Expression in Tomato by Trichoderma hamatum 382

First author: Department of Agri-Food Environmental and Microbiological Science and Technology, University of Molise, Campobasso, Italy; second, fourth, fifth, sixth, seventh, and eighth authors: Ohio Agricultural Research and Development Center, Ohio State University, Department of Plant Pathology, Wooster 44691; and third author: United States Department of Agriculture-Agricultural Research Service, Crop Production and Pest Control Unit, Department of Agronomy, Purdue University, Lilly Hall of Sciences, 915 West State Street, West Lafayette, IN 47907-2054

A light sphagnum peat mix inoculated with Trichoderma hamatum 382 consistently provided a significant (P = 0.05) degree of protection against bacterial spot of tomato and its pathogen Xanthomonas euvesicatoria 110c compared with the control peat mix, even though this biocontrol agent did not colonize aboveground plant parts. To gain insight into the mechanism by which T. hamatum 382 induced resistance in tomato, high-density oligonucleotide microarrays were used to determine its effect on the expression pattern of 15,925 genes in leaves just before they were inoculated with the pathogen. T. hamatum 382 consistently modulated the expression of genes in tomato leaves. We identified 45 genes to be differentially expressed across the replicated treatments, and 41 of these genes could be assigned to at least one of seven functional categories. T. hamatum 382-induced genes have functions associated with biotic or abiotic stress, as well as RNA, DNA, and protein metabolism. Four extensin and extensin-like proteins were induced. However, besides pathogenesis-related protein 5, the main markers of systemic acquired resistance were not significantly induced. This work showed that T. hamatum 382 actively induces systemic changes in plant physiology and disease resistance through systemic modulation of the expression of stress and metabolism genes.

Additional keywords: extensins, ISR, Lycopersicon esculentum, mechanism of induced resistance, microarray analysis, Solanum lycopersicum, X. campestris pv. vesicatoria.