Overexpression of the grapevine PGIP1 in tobacco results in compositional changes in the leaf arabinoxyloglucan network in the absence of fungal infection
1 Institute for Wine Biotechnology, Department of Viticulture and Oenology, Faculty of AgriSciences, Stellenbosch University, Matieland, 7602, South Africa
2 Energy Biosciences Institute, University of California, 2151 Berkeley Way, Berkeley, CA, 94720-5230, USA
3 Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, DK-, 1001, Denmark
4 Department of Microbiology, Stellenbosch University, Matieland, 7602, South Africa
5 Current address: Laboratoire Glycobiologie et Matrice Extracellulaire Végétale (Glyco-MEV). Grand Réseau de Recherche VASI de Haute Normandie, PRES Normandie Université. Université de Rouen, Mont Saint Aignan, 76821 Cedex, France
BMC Plant Biology 2013, 13:46 doi:10.1186/1471-2229-13-46Published: 18 March 2013
Constitutive 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.
To 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.
VvPGIP1 overexpression therefore results in cell wall remodeling and reorganization of the cellulose-xyloglucan network in tobacco in advance of potential infection.