BackgroundThe model grass Brachypodium distachyon is increasingly used to study various aspects of grass biology. A large and genotypically diverse collection of B. distachyon germplasm has been assembled by the research community. The natural variation in this collection can serve as a powerful experimental tool for many areas of inquiry, including investigating biomass traits.ResultsWe surveyed the phenotypic diversity in a large collection of inbred lines and then selected a core collection of lines for more detailed analysis with an emphasis on traits relevant to the use of grasses as biofuel and grain crops. Phenotypic characters examined included plant height, growth habit, stem density, flowering time, and seed weight. We also surveyed differences in cell wall composition using near infrared spectroscopy (NIR) and comprehensive microarray polymer profiling (CoMPP). In all cases, we observed extensive natural variation including a two-fold variation in stem density, four-fold variation in ferulic acid bound to hemicellulose, and 1.7-fold variation in seed mass.ConclusionThese characterizations can provide the criteria for selecting diverse lines for future investigations of the genetic basis of the observed phenotypic variation.
BackgroundConstitutive expression of Vitis vinifera polygalacturonase-inhibiting protein 1 (Vvpgip1) has been shown to protect tobacco plants against Botrytis cinerea. Evidence points to additional roles for VvPGIP1, beyond the classical endopolygalacturonase (ePG) inhibition mechanism, in providing protection against fungal infection. Gene expression and biochemical datasets previously obtained, in the absence of infection, point to the cell wall, and particularly the xyloglucan component of transgenic VvPGIP1 lines as playing a role in fungal resistance.ResultsTo elucidate the role of wall-associated processes in PGIP-derived resistance pre-infection, a wall profiling analysis, using high-throughput and fractionation techniques, was performed on healthy leaves from wild-type and previously characterized transgenic lines. The cell wall structure profile during development was found to be altered in the transgenic lines assessed versus the wild-type plants. Immunoprofiling revealed subtle changes in pectin and cellulose components and marked changes in the hemicellulose matrix, which showed reduced binding in transgenic leaves of VvPGIP1 expressing plants. Using an enzymatic xyloglucan oligosaccharide fingerprinting technique optimized for tobacco arabinoxyloglucans, we showed that polysaccharides of the XEG-soluble domain were modified in relative abundance for certain oligosaccharide components, although no differences in ion profiles were evident between wild-type and transgenic plants. These changes did not significantly influence plant morphology or normal growth processes compared to wild-type lines.ConclusionsVvPGIP1 overexpression therefore results in cell wall remodeling and reorganization of the cellulose-xyloglucan network in tobacco in advance of potential infection.
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