Abstract
BackgroundThe interaction of plants with endophytic symbiotic fungi in the genus Trichoderma alters the plant proteome and transcriptome and results in enhanced plant growth and resistance to diseases. In a previous study, we identified the numerous chitinolytic enzyme families and individual enzymes in maize which are implicated in plant disease resistance and other plant responses.ResultsWe examined the differential expression of the entire suite of chitinolytic enzymes in maize plants in the presence and absence of T. harzianum. Expression of these enzymes revealed a band of chitinolytic enzyme activity that had greater mass than any known chitinase. This study reports the characterization of this large protein. It was found to be a heretofore undiscovered heterodimer between an exo- and an endo-enzyme, and the endo portion differed between plants colonized with T. harzianum and those grown in its absence and between shoots and roots. The heterodimeric enzymes from shoots in the presence and absence of T. harzianum were purified and characterized. The dimeric enzyme from Trichoderma-inoculated plants had higher specific activity and greater ability to inhibit fungal growth than those from control plants. The activity of specific chitinolytic enzymes was higher in plants grown from Trichoderma treated seeds than in control plants.ConclusionsThis is the first report of a dimer between endo- and exochitinase. The endochitinase component of the dimer changed post Trichoderma inoculation. The dimer originating from Trichoderma inoculated plants had a higher antifungal activity than the comparable enzyme from control plants.
Highlights
The interaction of plants with endophytic symbiotic fungi in the genus Trichoderma alters the plant proteome and transcriptome and results in enhanced plant growth and resistance to diseases
Chitin degrading enzymes of maize are different in shoots and roots and in the presence and absence of T. harzianum Maize chitinolytic enzymes obtained from roots and shoots of plants grown from seeds treated or not treated with T. harzianum strain Trichoderma harzianum Rifai strain 22 (T22) were tested for activity in gels
The activity bands in shoots decreased to three, and the pattern changed in roots (Fig. 1). In both shoots and roots, activity of almost all bands was higher in the presence than in the absence of T. harzianum
Summary
The interaction of plants with endophytic symbiotic fungi in the genus Trichoderma alters the plant proteome and transcriptome and results in enhanced plant growth and resistance to diseases. We identified the numerous chitinolytic enzyme families and individual enzymes in maize which are implicated in plant disease resistance and other plant responses. Trichoderma spp. are opportunistic root colonizing fungal plant symbionts [1] that induce numerous changes in plant gene expression and physiology. In an earlier study we determined that maize root colonization enhanced expression of chitinolytic enzyme activity [15]. This is frequently assumed to be part of induced systemic resistance [8]. Using a combination of in silico and expression analyses, we identified putative 27 endochitinase genes (glycosyl hydrolases families 18 and 19) and four exochitinases (GH20; β-Nacetylhexosaminidases). The full sequences of these genes, domain analyses, and, in many cases, chromosomal locations were identified for these genes [16]
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