Browsing by Author "Willats, William G. T."

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    The impact of carbohydrate-active enzymes on mediating cell wall polysaccharide-tannin interactions in a wine-like matrix
    (Elsevier, 2019-12-14) Osete-Alcaraz, Andrea; Gomez-Plaza, Encarna; Martinez-Perez, Pilar; Weiller, Florent; Schuckel, Julia; Willats, William G. T.; Moore, John P.; Ros-Garcia, Jose M.; Bautista-Ortin, Ana B.
    Tannins are present in grape skins and seeds from where they are transferred into the must-wine matrix during the maceration stages of winemaking. However, tannin transfer is often incomplete. This could be due, among other reasons, to tannins becoming bound to grape cell wall polysaccharides, including soluble polymers, which are released during vinification and are present in high concentrations in the must/wine. The use of cell wall deconstructing enzymes offers the possibility of reducing these interactions, releasing more tannins into the final wine. The main aim of this study was to evaluate the optimal addition (individually, in combination or sequentially) of hydrolytic enzymes that would prevent tight polysaccharide-tannin associations. The use of comprehensive microarray polymer profiling (CoMPP) methodology provided key insights into how the enzyme treatments impacted the grape cell wall matrix and tannin binding. The results demonstrated that poly-galacturonase + pectin-lyase promoted the highest release of tannins into solution.
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    Overexpression of the grapevine PGIP1 in tobacco results in compositional changes in the leaf arabinoxyloglucan network in the absence of fungal infection
    (BioMed Central, 2013-03) Nguema-Ona, Eric; Moore, John P.; Fagerstrom, Alexandra D.; Fangel, Jonatan U.; Willats, William G. T.; Hugo, Annatjie; Vivier, Melane A.
    Abstract Background 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. Results 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. Conclusions VvPGIP1 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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    Overexpression of VviPGIP1 and NtCAD14 in tobacco screened using glycan microarrays reveals cell wall reorganisation in the absence of fungal infection
    (MDPI, 2020-07-15) Weiller, Florent; Gerber, Lorenz; Trygg, Johan; Fangel, Jonatan U.; Willats, William G. T.; Driouich, Azeddine; Vivier, Melane A.; Moore, John P.
    The expression of Vitis vinifera polygalacturonase inhibiting protein 1 (VviPGIP1) in Nicotiana tabacum has been linked to modifications at the cell wall level. Previous investigations have shown an upregulation of the lignin biosynthesis pathway and reorganisation of arabinoxyloglucan composition. This suggests cell wall tightening occurs, which may be linked to defence priming responses. The present study used a screening approach to test four VviPGIP1 and four NtCAD14 overexpressing transgenic lines for cell wall alterations. Overexpressing the tobacco-derived cinnamyl alcohol dehydrogenase (NtCAD14) gene is known to increase lignin biosynthesis and deposition. These lines, particularly PGIP1 expressing plants, have been shown to lead to a decrease in susceptibility towards grey rot fungus Botrytis cinerea. In this study the aim was to investigate the cell wall modulations that occurred prior to infection, which should highlight potential priming phenomena and phenotypes. Leaf lignin composition and relative concentration of constituent monolignols were evaluated using pyrolysis gas chromatography. Significant concentrations of lignin were deposited in the stems but not the leaves of NtCAD14 overexpressing plants. Furthermore, no significant changes in monolignol composition were found between transgenic and wild type plants. The polysaccharide modifications were quantified using gas chromatography (GC–MS) of constituent monosaccharides. The major leaf polysaccharide and cell wall protein components were evaluated using comprehensive microarray polymer profiling (CoMPP). The most significant changes appeared at the polysaccharide and protein level. The pectin fraction of the transgenic lines had subtle variations in patterning for methylesterification epitopes for both VviPGIP1 and NtCAD14 transgenic lines versus wild type. Pectin esterification levels have been linked to pathogen defence in the past. The most marked changes occurred in glycoprotein abundance for both the VviPGIP1 and NtCAD14 lines. Epitopes for arabinogalactan proteins (AGPs) and extensins were notably altered in transgenic NtCAD14 tobacco.