John Moore | Stellenbosch University (original) (raw)

Papers by John Moore

Research paper thumbnail of Overexpression of VviPGIP1 and NtCAD14 in Tobacco Screened Using Glycan Microarrays Reveals Cell Wall Reorganisation in the Absence of Fungal Infection

Vaccines, 2020

The expression of Vitis vinifera polygalacturonase inhibiting protein 1 (VviPGIP1) in Nicotiana t... more 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 li...

Research paper thumbnail of The phenolic profile extracted from the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia using Natural Deep Eutectic Solvents varies according to the solvation conditions

Phytochemistry, 2020

Natural Deep Eutectic Solvents (NaDES) have been proposed as designer solvents for the green extr... more Natural Deep Eutectic Solvents (NaDES) have been proposed as designer solvents for the green extraction of bioactive products from plants. Myrothamnus flabellifolia is a desiccation-tolerant medicinal shrub that has been widely studied for its phenolic properties; however, a NaDES-based approach for the extraction of phenolics has not been tested in this species. Our aim was thus to evaluate the extraction of phenolics from M. flabellifolia using four different NaDES with differing acidities using a non-targeted liquid chromatography-quantitative time-offlight-tandem mass spectrometry (LC-QTOF-MS/MS) metabolomics approach. Anthocyanin pigments were quantified using targeted high-performance LC. Leaf material from M. flabellifolia was extracted in four different NaDES solutions (sucrose-fructose-glucose; proline-malic acid; sucrose-citric acid; and glucose-choline chloride), and the results were subjected to multivariate statistical analysis to evaluate the phenolic profiles of the different NaDES extracts. The NaDES were effective at extracting phenolic compounds from M. flabellifolia and also exhibited specificity in the suites of phenolics that they extracted, as indicated by principal component analysis. Using partial least squares-discriminant analysis, we were able to identify the phenolics that were most differentially abundant between the extracts, and a heatmap provided an indication of the types of phenolics that were extracted by the different NaDES. Furthermore, the NaDES also extracted several compounds not previously detected in M. flabellifolia using conventional organic solvents, demonstrating their use in compound discovery. The NaDES also differentially targeted anthocyanins, with the more acidic NaDES extracting higher quantities of anthocyanins and polymeric pigments. A green chemistry-based extraction technique using NaDES can thus effectively target phenolics in M. flabellifolia and offers a promising solution for future phytochemical investigations in medicinal plants using a highly efficient non-toxic solvent system that can be tailored to target particular compounds.

Research paper thumbnail of Metabolomic Profiling of the Desiccation-Tolerant Medicinal Shrub Myrothamnus flabellifolia Indicates Phenolic Variability Across Its Natural Habitat: Implications for Tea and Cosmetics Production

Molecules, 2019

The leaves and twigs of the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia are ha... more The leaves and twigs of the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia are harvested for use in traditional and commercial teas and cosmetics due to their phenolic properties. The antioxidant and pharmacological value of this plant has been widely confirmed; however, previous studies typically based their findings on material collected from a single region. The existence of phenolic variability between plants from different geographical regions experiencing different rainfall regimes has thus not been sufficiently evaluated. Furthermore, the anthocyanins present in this plant have not been assessed. The present study thus used an untargeted liquid chromatography-tandem-mass spectrometry approach to profile phenolics in M. flabellifolia material collected from three climatically distinct (high, moderate, and low rainfall) regions representing the western, southern, and eastern extent of the species range in southern Africa. Forty-one putative phenolic compounds, p...

Research paper thumbnail of Metabolomics as a complement to phylogenetics for assessing intraspecific boundaries in the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia (Myrothamnaceae)

Phytochemistry, 2019

The desiccation-tolerant shrub Myrothamnus flabellifolia has colonised a unique and harsh niche t... more The desiccation-tolerant shrub Myrothamnus flabellifolia has colonised a unique and harsh niche that provides little protection from the elements. It has a wide distribution range in southern Africa, occurring across an environmental gradient that is exceptionally arid in the southwest and highly mesic in the northeast. It is also harvested for use in medicinal preparations, both traditionally and commercially. However, the phytochemical variability of plants from different rainfall regions has not been assessed, nor have the intraspecific relationships been evaluated by means of a rigorously tested phylogeny. The aims of the present study were thus (1) to test a phylogenetic hypothesis for intraspecific relationships in M. flabellifolia; (2) to assess, based on the global metabolomic profiles, whether accessions collected from the three different geographic locations in southern Africa across a rainfall gradient can be differentiated, and if this corroborates the phylogenetic signature; and (3) with the aid of multivariate statistical analysis, identify and evaluate the most significant discriminatory metabolites between the three sampled regions that could act as potential barcodes. The results show that the phylogenetic and metabolomic signatures were congruent, and the metabolomic data were better able to discriminate the different populations collected from the three regions. Several potential barcodes for discriminating the material from the three regions are proposed. Quercetin-rhamnoside and 3-O-methylquercetin, both significant antioxidants, were present at significantly higher quantities in the material from the driest region in the west than from the more mesic regions in the south and east, whereas quercetin-3-O-glucuronide was significantly higher in the latter. A naringenin-like compound or arbutin derivative could discriminate the southern samples from the eastern samples, whereas digalloylglucose differentiated the eastern samples from the southern samples. In summary, the findings of this study imply that the origin of the material should be considered when used in medicinal and cosmetic preparations.

Research paper thumbnail of Investigating the relationship between cell wall polysaccharide composition and the extractability of grape phenolic compounds into Shiraz wines. Part II: Extractability during fermentation into wines made from grapes of different ripeness levels

Research paper thumbnail of Investigating the relationship between grape cell wall polysaccharide composition and the extractability of phenolic compounds into Shiraz wines. Part I: Vintage and ripeness effects

Food Chemistry, 2019

Phenolic compounds play an important role in colour stability and sensory properties of red wine.... more Phenolic compounds play an important role in colour stability and sensory properties of red wine. This study evaluated berry skin cell wall composition and how this influences grape and wine phenolics at different ripeness levels (21ºBrix, 23ºBrix, and 25ºBrix) over two consecutive vintages. The vintage effect was highly significant, especially in the pectin fraction of the grape cell walls and affected the concentrations of certain phenolics extracted. The climatic variance between the seasons might have influenced the differences observed in the grape cell wall compositions. Firstly, a higher grape and wine phenolic content, especially in polymeric phenols, was found in 2015 wines. Additionally, grape berry cell walls, especially at the earliest stages of ripening, were found to be more intact in 2015 than in 2016. Thus, a possible relationship was found between the 2 degree of berry intactness, especially for pectin-rich components, and the corresponding phenolic extractability during the winemaking.

Research paper thumbnail of Combining hydrothermal pretreatment with enzymes de-pectinates and exposes the innermost xyloglucan-rich hemicellulose layers of wine grape pomace

Food chemistry, 2017

Chardonnay grape pomace was treated with pressurized heat followed by enzymatic hydrolysis, with ... more Chardonnay grape pomace was treated with pressurized heat followed by enzymatic hydrolysis, with commercial or pure enzymes, in buffered conditions. The pomace was unfermented as commonly found for white winemaking wastes and treatments aimed to simulate biovalorization processing. Cell wall profiling techniques showed that the pretreatment led to depectination of the outer layers thereby exposing xylan polymers and increasing the extractability of arabinans, galactans, arabinogalactan proteins and mannans. This higher extractability is believed to be linked with partial degradation and opening-up of cell wall networks. Pectinase-rich enzyme preparations were presumably able to access the inner rhamnogalacturonan I dominant coating layers due to the hydrothermal pretreatment. Patterns of epitope abundance and the sequential release of cell wall polymers with specific combinations of enzymes led to a working model of the hitherto, poorly understood innermost xyloglucan-rich hemicellu...

Research paper thumbnail of Effect of commercial enzymes on berry cell wall deconstruction in the context of intra-vineyard ripeness variation under winemaking conditions

Journal of agricultural and food chemistry, Jan 28, 2016

Significant intra-vineyard variation in grape berry ripening occurs within vines and between vine... more Significant intra-vineyard variation in grape berry ripening occurs within vines and between vines. However, no cell wall data is available on such variation. Here we used a chequered-board-panel-design to investigate ripening variation in pooled grape bunches for enzyme-assisted winemaking. The vineyard was dissected into defined panels which were selected for winemaking with or without enzyme addition. Cell wall material was prepared and subjected to high-throughput profiling combined with multivariate data analysis. The study showed that significant ripening-related variation was present at the berry cell wall polymer level and occurred within the experimental vineyard block. Furthemore, all enzyme treatments reduced cell wall variation via de-pectination. Interestingly, cell wall esterification levels were unaffected by enzyme treatments. This study provides clear evidence that enzymes can positively influence the consistency of winemaking and provides a foundation for further r...

Research paper thumbnail of A multivariate approach using ATR mid-infrared spectroscopy to measure the surface mannoproteins and β-glucans of yeast cell walls during wine fermentations

Journal of agricultural and food chemistry, Jan 21, 2015

Yeast cells possess a cell wall comprising primarily glycoproteins, mannans and glucan polymers. ... more Yeast cells possess a cell wall comprising primarily glycoproteins, mannans and glucan polymers. Several yeast phenotypes relevant for fermentation, wine processing and wine quality are correlated with cell wall properties. To investigate the effect of wine fermentation on cell wall composition, a study was performed using mid-infrared (MIR) spectroscopy coupled with multivariate methods (i.e. PCA and OPLS-DA). A total of 40 yeast strains were evaluated, including Saccharomyces strains (laboratory and industrial) and non-Saccharomyces species. Cells were fermented in both synthetic MS300 and Chardonnay grape must to stationery phase, processed and scanned in MIR spectrum. PCA of the fingerprint spectral region showed distinct separation of Saccharomyces strains from non-Saccharomyces species; furthermore industrial wine yeast strains separated from laboratory strains. PCA loading plots and the use of OPLS-DA to the datasets suggested that industrial strains were enriched with cell w...

Research paper thumbnail of Editorial: Current advances and challenges in understanding plant desiccation tolerance

Frontiers in Plant Science, 2015

Research paper thumbnail of Profiling the Hydrolysis of Isolated Grape Berry Skin Cell Walls by Purified Enzymes

Journal of Agricultural and Food Chemistry, 2015

The unraveling of crushed grapes by maceration enzymes during winemaking is difficult to study be... more The unraveling of crushed grapes by maceration enzymes during winemaking is difficult to study because of the complex and rather undefined nature of both the substrate and the enzyme preparations. In this study we simplified both the substrate, by using isolated grape skin cell walls, and the enzyme preparations, by using purified enzymes in buffered conditions, to carefully follow the impact of the individual and combined enzymes on the grape skin cell walls. By using cell wall profiling techniques we could monitor the compositional changes in the grape cell wall polymers due to enzyme activity. Extensive enzymatic hydrolysis, achieved with a preparation of pectinases or pectinases combined with cellulase or hemicellulase enzymes, completely removed or drastically reduced levels of pectin polymers, whereas less extensive hydrolysis only opened up the cell wall structure and allowed extraction of polymers from within the cell wall layers. Synergistic enzyme activity was detectable as well as indications of specific cell wall polymer associations.

Research paper thumbnail of A role for pectin-associated arabinans in maintaining the flexibility of the plant cell wall during water deficit stress

Plant Signaling & Behavior, 2008

Research paper thumbnail of Dissecting the polysaccharide-rich grape cell wall changes during winemaking using combined high-throughput and fractionation methods

Carbohydrate Polymers, 2015

Limited information is available on grape wall-derived polymeric structure/composition and how th... more Limited information is available on grape wall-derived polymeric structure/composition and how this changes during fermentation. Commercial winemaking operations use enzymes that target the polysaccharide-rich polymers of the cell walls of grape tissues to clarify musts and extract pigments during the fermentations. In this study, we have assessed changes in polysaccharide composition/turnover throughout the winemaking process by applying recently developed cell wall profiling approaches for monosaccharide composition (GC-MS), infra-red (IR) spectroscopy and comprehensive microarray polymer profiling (CoMPP). CoMPP performed on the concentrated soluble wine polysaccharides showed a fraction rich in rhamnogalacturonan I (RGI), homogalacturonan (HG) and arabinogalactan proteins (AGPs). We also used chemical and enzymatic fractionation techniques in addition to CoMPP to understand the berry deconstruction process more in-depth. CoMPP and gravimetric analysis of the fractionated pomace used aqueous buffers and CDTA solutions to obtain a pectin-rich fraction (pulp tightly-bound to skins) containing HG, RGI and AGPs; and then alkali (sodium carbonate and potassium hydroxide), liberating a xyloglucan-rich fraction (mainly skins). Interestingly this fraction was found to include pectins consisting of tightly associated and highly methyl-esterified HG and RGI networks. This was supported by enzymatic fractionation targeting pectin and xyloglucan polymers. A unique aspect is datasets suggesting that enzyme-resistant pectin polymers 'coat' the inner xyloglucan-rich skin cells. This data has important implications for developing effective strategies for efficient release of favorable compounds (pigments, tannins, aromatics, etc.) from the berry tissues during winemaking. This study provides a framework to understand the complex interactions between the grape matrix and carbohydrate-active enzymes to produce wine of desired quality and consistency.

Research paper thumbnail of The resurrection plant, Myrothamnus flabellifolius: one species or many?: classifying plants

Research paper thumbnail of Following the Compositional Changes of Fresh Grape Skin Cell Walls during the Fermentation Process in the Presence and Absence of Maceration Enzymes

Journal of Agricultural and Food Chemistry, 2015

Cell wall profiling technologies were used to follow compositional changes that occurred in the s... more Cell wall profiling technologies were used to follow compositional changes that occurred in the skins of grape berries (from two different ripeness levels) during fermentation and enzyme maceration. Multivariate data analysis showed that the fermentation process yielded cell walls enriched in hemicellulose components because pectin was solubilized (and removed) with a reduction as well as exposure of cell wall proteins usually embedded within the cell wall structure. The addition of enzymes caused even more depectination and the enzymes unravelled the cell walls enabling better access to, and extraction of, all cell wall polymers. Overripe grapes had cell walls that were extensively hydrolysed and depolymerized probably by natural grape tissue ripening enzymes and this enhanced the impact that the maceration enzymes had on the cell wall monosaccharide profile. The combination of the techniques that were used is an effective direct measurement of the hydrolysis actions of maceration enzymes on the cell walls of grape berry skin.

Research paper thumbnail of A Systems-Based Molecular Biology Analysis of Resurrection Plants for Crop and Forage Improvement in Arid Environments

John P. Moore and Jill M. FarrantResurrection plants represent a remarkable group of plants posse... more John P. Moore and Jill M. FarrantResurrection plants represent a remarkable group of plants possessing vegetativetissuecapableofsurvivingwaterlosstoanair-drystate.Manyofthesespeciesgrowinsemiarid and arid countries, and a rich diversity is found in Southern Africa. Wereviewthemechanismsproposedtoexplainhowtheytoleratedesiccation,highlight-ingtheprocessesthatprotectthemfrommetabolicdisruption,oxidativedamage,andmechanicalstressduringdehydration.Alsoreviewedarethemolecularmechanismsassociated with sensing water deficit and activating transcriptional processes asso-ciated with desiccation-induced gene expression in these species. Functional genes,whichencodeprotectivemacromoleculesandenzymes,andthesystemsapproaches(transcriptomics and proteomics) utilized are also discussed. The application ofresurrection plant studies in the molecular engineering of valuable crop plants andpotentially providing new forages is highlighted.17.1IntroductionTheabilityoforganismstosurviveextremedehydration(i.e.,desiccation),referredtoas anhydrobiosis (i.e., life without water), has evolved on multiple occasions in theplant,animal,fungal,andmicrobialkingdoms.Anumberofhigherplants,tracheo-phytes, were found to be capable of tolerating desiccation and so these differentspecies became collectively referred to as “resurrection plants” [1, 2]. The nameresurrectionplantoriginatesfromtheobservationoftheseplantsduringrehydrationand denotes the seemingly miraculous manner by which the leaves and stems of adesiccated resurrection plant unfolds and regreens upon water availability.Desiccation tolerance is generally defined as “the ability to survive drying to, orbelow, the absolute water content of 0.1g H

Research paper thumbnail of An overview of the biology of the desiccation-tolerant resurrection plant Myrothamnus flabellifolia

Annals of botany, 2007

Myrothamnus flabellifolia is unique as the only woody resurrection plant. It is an important plan... more Myrothamnus flabellifolia is unique as the only woody resurrection plant. It is an important plant in southern Africa because of its widespread occurrence and usage in African medicine and traditional culture. Many reports have investigated facets of its biology and the mechanisms associated with its desiccation tolerance. The general biology of the woody resurrection plant Myrothamnus flabellifolia is reviewed. The review focuses on the geography and ecology, systematic placement, evolution, morphology and reproductive ecology of M. flabellifolia as well as the wood anatomy and re-filling mechanism. In addition, the desiccation tolerance, ethnobotanical importance and medicinal properties of the plant are reviewed. Also, future research avenues are suggested, in particular the necessity to research the biogeography and systematics of the species and the role of the polyphenols present, as well as the molecular basis of the plant's desiccation tolerance.

Research paper thumbnail of Towards a systems-based understanding of plant desiccation tolerance

Trends in Plant Science, 2009

Research paper thumbnail of Arabinose-rich polymers as an evolutionary strategy to plasticize resurrection plant cell walls against desiccation

Planta, 2012

A variety of Southern African resurrection plants were surveyed using high-throughput cell wall p... more A variety of Southern African resurrection plants were surveyed using high-throughput cell wall profiling tools. Species evaluated were the dicotyledons, Myrothamnus flabellifolia and Craterostigma plantagineum; the monocotyledons, Xerophyta viscosa, Xerophyta schlecterii, Xerophyta humilis and the resurrection grass Eragrostis nindensis, as well as a pteridophyte, the resurrection fern, Mohria caffrorum. Comparisons were made between hydrated and desiccated leaf and frond material, with respect to cell wall composition and polymer abundance, using monosaccharide composition analysis, FT-IR spectroscopy and comprehensive microarray polymer profiling in combination with multivariate data analysis. The data obtained suggest that three main functional strategies appear to have evolved to prepare plant cell walls for desiccation. Arabinan-rich pectin and arabinogalactan proteins are found in the resurrection fern M. caffrorum and the basal angiosperm M. flabellifolia where they appear to act as 'pectic plasticizers'. Dicotyledons with pectin-rich walls, such as C. plantagineum, seem to use inducible mechanisms which consist of up-regulating wall proteins and osmoprotectants. The hemicellulose-rich walls of the grass-like Xerophyta spp. and the resurrection grass E. nindensis were found to contain highly arabinosylated xylans and arabinogalactan proteins. These data support a general mechanism of 'plasticising' the cell walls of resurrection plants to desiccation and implicate arabinose-rich polymers (pectin-arabinans, arabinogalactan proteins and arabinoxylans) as the major contributors in ensuring flexibility is maintained and rehydration is facilitated in these plants.

Research paper thumbnail of Response of the Leaf Cell Wall to Desiccation in the Resurrection Plant Myrothamnus flabellifolius

Plant Physiology, 2006

The Myrothamnus flabellifolius leaf cell wall and its response to desiccation were investigated u... more The Myrothamnus flabellifolius leaf cell wall and its response to desiccation were investigated using electron microscopic, biochemical, and immunocytochemical techniques. Electron microscopy revealed desiccation-induced cell wall folding in the majority of mesophyll and epidermal cells. Thick-walled vascular tissue and sclerenchymous ribs did not fold and supported the surrounding tissue, thereby limiting the extent of leaf shrinkage and allowing leaf morphology to be rapidly regained upon rehydration. Isolated cell walls from hydrated and desiccated M. flabellifolius leaves were fractionated into their constituent polymers and the resulting fractions were analyzed for monosaccharide content. Significant differences between hydrated and desiccated states were observed in the water-soluble buffer extract, pectin fractions, and the arabinogalactan protein-rich extract. A marked increase in galacturonic acid was found in the alkali-insoluble pectic fraction. Xyloglucan structure was a...

Research paper thumbnail of Overexpression of VviPGIP1 and NtCAD14 in Tobacco Screened Using Glycan Microarrays Reveals Cell Wall Reorganisation in the Absence of Fungal Infection

Vaccines, 2020

The expression of Vitis vinifera polygalacturonase inhibiting protein 1 (VviPGIP1) in Nicotiana t... more 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 li...

Research paper thumbnail of The phenolic profile extracted from the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia using Natural Deep Eutectic Solvents varies according to the solvation conditions

Phytochemistry, 2020

Natural Deep Eutectic Solvents (NaDES) have been proposed as designer solvents for the green extr... more Natural Deep Eutectic Solvents (NaDES) have been proposed as designer solvents for the green extraction of bioactive products from plants. Myrothamnus flabellifolia is a desiccation-tolerant medicinal shrub that has been widely studied for its phenolic properties; however, a NaDES-based approach for the extraction of phenolics has not been tested in this species. Our aim was thus to evaluate the extraction of phenolics from M. flabellifolia using four different NaDES with differing acidities using a non-targeted liquid chromatography-quantitative time-offlight-tandem mass spectrometry (LC-QTOF-MS/MS) metabolomics approach. Anthocyanin pigments were quantified using targeted high-performance LC. Leaf material from M. flabellifolia was extracted in four different NaDES solutions (sucrose-fructose-glucose; proline-malic acid; sucrose-citric acid; and glucose-choline chloride), and the results were subjected to multivariate statistical analysis to evaluate the phenolic profiles of the different NaDES extracts. The NaDES were effective at extracting phenolic compounds from M. flabellifolia and also exhibited specificity in the suites of phenolics that they extracted, as indicated by principal component analysis. Using partial least squares-discriminant analysis, we were able to identify the phenolics that were most differentially abundant between the extracts, and a heatmap provided an indication of the types of phenolics that were extracted by the different NaDES. Furthermore, the NaDES also extracted several compounds not previously detected in M. flabellifolia using conventional organic solvents, demonstrating their use in compound discovery. The NaDES also differentially targeted anthocyanins, with the more acidic NaDES extracting higher quantities of anthocyanins and polymeric pigments. A green chemistry-based extraction technique using NaDES can thus effectively target phenolics in M. flabellifolia and offers a promising solution for future phytochemical investigations in medicinal plants using a highly efficient non-toxic solvent system that can be tailored to target particular compounds.

Research paper thumbnail of Metabolomic Profiling of the Desiccation-Tolerant Medicinal Shrub Myrothamnus flabellifolia Indicates Phenolic Variability Across Its Natural Habitat: Implications for Tea and Cosmetics Production

Molecules, 2019

The leaves and twigs of the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia are ha... more The leaves and twigs of the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia are harvested for use in traditional and commercial teas and cosmetics due to their phenolic properties. The antioxidant and pharmacological value of this plant has been widely confirmed; however, previous studies typically based their findings on material collected from a single region. The existence of phenolic variability between plants from different geographical regions experiencing different rainfall regimes has thus not been sufficiently evaluated. Furthermore, the anthocyanins present in this plant have not been assessed. The present study thus used an untargeted liquid chromatography-tandem-mass spectrometry approach to profile phenolics in M. flabellifolia material collected from three climatically distinct (high, moderate, and low rainfall) regions representing the western, southern, and eastern extent of the species range in southern Africa. Forty-one putative phenolic compounds, p...

Research paper thumbnail of Metabolomics as a complement to phylogenetics for assessing intraspecific boundaries in the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia (Myrothamnaceae)

Phytochemistry, 2019

The desiccation-tolerant shrub Myrothamnus flabellifolia has colonised a unique and harsh niche t... more The desiccation-tolerant shrub Myrothamnus flabellifolia has colonised a unique and harsh niche that provides little protection from the elements. It has a wide distribution range in southern Africa, occurring across an environmental gradient that is exceptionally arid in the southwest and highly mesic in the northeast. It is also harvested for use in medicinal preparations, both traditionally and commercially. However, the phytochemical variability of plants from different rainfall regions has not been assessed, nor have the intraspecific relationships been evaluated by means of a rigorously tested phylogeny. The aims of the present study were thus (1) to test a phylogenetic hypothesis for intraspecific relationships in M. flabellifolia; (2) to assess, based on the global metabolomic profiles, whether accessions collected from the three different geographic locations in southern Africa across a rainfall gradient can be differentiated, and if this corroborates the phylogenetic signature; and (3) with the aid of multivariate statistical analysis, identify and evaluate the most significant discriminatory metabolites between the three sampled regions that could act as potential barcodes. The results show that the phylogenetic and metabolomic signatures were congruent, and the metabolomic data were better able to discriminate the different populations collected from the three regions. Several potential barcodes for discriminating the material from the three regions are proposed. Quercetin-rhamnoside and 3-O-methylquercetin, both significant antioxidants, were present at significantly higher quantities in the material from the driest region in the west than from the more mesic regions in the south and east, whereas quercetin-3-O-glucuronide was significantly higher in the latter. A naringenin-like compound or arbutin derivative could discriminate the southern samples from the eastern samples, whereas digalloylglucose differentiated the eastern samples from the southern samples. In summary, the findings of this study imply that the origin of the material should be considered when used in medicinal and cosmetic preparations.

Research paper thumbnail of Investigating the relationship between cell wall polysaccharide composition and the extractability of grape phenolic compounds into Shiraz wines. Part II: Extractability during fermentation into wines made from grapes of different ripeness levels

Research paper thumbnail of Investigating the relationship between grape cell wall polysaccharide composition and the extractability of phenolic compounds into Shiraz wines. Part I: Vintage and ripeness effects

Food Chemistry, 2019

Phenolic compounds play an important role in colour stability and sensory properties of red wine.... more Phenolic compounds play an important role in colour stability and sensory properties of red wine. This study evaluated berry skin cell wall composition and how this influences grape and wine phenolics at different ripeness levels (21ºBrix, 23ºBrix, and 25ºBrix) over two consecutive vintages. The vintage effect was highly significant, especially in the pectin fraction of the grape cell walls and affected the concentrations of certain phenolics extracted. The climatic variance between the seasons might have influenced the differences observed in the grape cell wall compositions. Firstly, a higher grape and wine phenolic content, especially in polymeric phenols, was found in 2015 wines. Additionally, grape berry cell walls, especially at the earliest stages of ripening, were found to be more intact in 2015 than in 2016. Thus, a possible relationship was found between the 2 degree of berry intactness, especially for pectin-rich components, and the corresponding phenolic extractability during the winemaking.

Research paper thumbnail of Combining hydrothermal pretreatment with enzymes de-pectinates and exposes the innermost xyloglucan-rich hemicellulose layers of wine grape pomace

Food chemistry, 2017

Chardonnay grape pomace was treated with pressurized heat followed by enzymatic hydrolysis, with ... more Chardonnay grape pomace was treated with pressurized heat followed by enzymatic hydrolysis, with commercial or pure enzymes, in buffered conditions. The pomace was unfermented as commonly found for white winemaking wastes and treatments aimed to simulate biovalorization processing. Cell wall profiling techniques showed that the pretreatment led to depectination of the outer layers thereby exposing xylan polymers and increasing the extractability of arabinans, galactans, arabinogalactan proteins and mannans. This higher extractability is believed to be linked with partial degradation and opening-up of cell wall networks. Pectinase-rich enzyme preparations were presumably able to access the inner rhamnogalacturonan I dominant coating layers due to the hydrothermal pretreatment. Patterns of epitope abundance and the sequential release of cell wall polymers with specific combinations of enzymes led to a working model of the hitherto, poorly understood innermost xyloglucan-rich hemicellu...

Research paper thumbnail of Effect of commercial enzymes on berry cell wall deconstruction in the context of intra-vineyard ripeness variation under winemaking conditions

Journal of agricultural and food chemistry, Jan 28, 2016

Significant intra-vineyard variation in grape berry ripening occurs within vines and between vine... more Significant intra-vineyard variation in grape berry ripening occurs within vines and between vines. However, no cell wall data is available on such variation. Here we used a chequered-board-panel-design to investigate ripening variation in pooled grape bunches for enzyme-assisted winemaking. The vineyard was dissected into defined panels which were selected for winemaking with or without enzyme addition. Cell wall material was prepared and subjected to high-throughput profiling combined with multivariate data analysis. The study showed that significant ripening-related variation was present at the berry cell wall polymer level and occurred within the experimental vineyard block. Furthemore, all enzyme treatments reduced cell wall variation via de-pectination. Interestingly, cell wall esterification levels were unaffected by enzyme treatments. This study provides clear evidence that enzymes can positively influence the consistency of winemaking and provides a foundation for further r...

Research paper thumbnail of A multivariate approach using ATR mid-infrared spectroscopy to measure the surface mannoproteins and β-glucans of yeast cell walls during wine fermentations

Journal of agricultural and food chemistry, Jan 21, 2015

Yeast cells possess a cell wall comprising primarily glycoproteins, mannans and glucan polymers. ... more Yeast cells possess a cell wall comprising primarily glycoproteins, mannans and glucan polymers. Several yeast phenotypes relevant for fermentation, wine processing and wine quality are correlated with cell wall properties. To investigate the effect of wine fermentation on cell wall composition, a study was performed using mid-infrared (MIR) spectroscopy coupled with multivariate methods (i.e. PCA and OPLS-DA). A total of 40 yeast strains were evaluated, including Saccharomyces strains (laboratory and industrial) and non-Saccharomyces species. Cells were fermented in both synthetic MS300 and Chardonnay grape must to stationery phase, processed and scanned in MIR spectrum. PCA of the fingerprint spectral region showed distinct separation of Saccharomyces strains from non-Saccharomyces species; furthermore industrial wine yeast strains separated from laboratory strains. PCA loading plots and the use of OPLS-DA to the datasets suggested that industrial strains were enriched with cell w...

Research paper thumbnail of Editorial: Current advances and challenges in understanding plant desiccation tolerance

Frontiers in Plant Science, 2015

Research paper thumbnail of Profiling the Hydrolysis of Isolated Grape Berry Skin Cell Walls by Purified Enzymes

Journal of Agricultural and Food Chemistry, 2015

The unraveling of crushed grapes by maceration enzymes during winemaking is difficult to study be... more The unraveling of crushed grapes by maceration enzymes during winemaking is difficult to study because of the complex and rather undefined nature of both the substrate and the enzyme preparations. In this study we simplified both the substrate, by using isolated grape skin cell walls, and the enzyme preparations, by using purified enzymes in buffered conditions, to carefully follow the impact of the individual and combined enzymes on the grape skin cell walls. By using cell wall profiling techniques we could monitor the compositional changes in the grape cell wall polymers due to enzyme activity. Extensive enzymatic hydrolysis, achieved with a preparation of pectinases or pectinases combined with cellulase or hemicellulase enzymes, completely removed or drastically reduced levels of pectin polymers, whereas less extensive hydrolysis only opened up the cell wall structure and allowed extraction of polymers from within the cell wall layers. Synergistic enzyme activity was detectable as well as indications of specific cell wall polymer associations.

Research paper thumbnail of A role for pectin-associated arabinans in maintaining the flexibility of the plant cell wall during water deficit stress

Plant Signaling & Behavior, 2008

Research paper thumbnail of Dissecting the polysaccharide-rich grape cell wall changes during winemaking using combined high-throughput and fractionation methods

Carbohydrate Polymers, 2015

Limited information is available on grape wall-derived polymeric structure/composition and how th... more Limited information is available on grape wall-derived polymeric structure/composition and how this changes during fermentation. Commercial winemaking operations use enzymes that target the polysaccharide-rich polymers of the cell walls of grape tissues to clarify musts and extract pigments during the fermentations. In this study, we have assessed changes in polysaccharide composition/turnover throughout the winemaking process by applying recently developed cell wall profiling approaches for monosaccharide composition (GC-MS), infra-red (IR) spectroscopy and comprehensive microarray polymer profiling (CoMPP). CoMPP performed on the concentrated soluble wine polysaccharides showed a fraction rich in rhamnogalacturonan I (RGI), homogalacturonan (HG) and arabinogalactan proteins (AGPs). We also used chemical and enzymatic fractionation techniques in addition to CoMPP to understand the berry deconstruction process more in-depth. CoMPP and gravimetric analysis of the fractionated pomace used aqueous buffers and CDTA solutions to obtain a pectin-rich fraction (pulp tightly-bound to skins) containing HG, RGI and AGPs; and then alkali (sodium carbonate and potassium hydroxide), liberating a xyloglucan-rich fraction (mainly skins). Interestingly this fraction was found to include pectins consisting of tightly associated and highly methyl-esterified HG and RGI networks. This was supported by enzymatic fractionation targeting pectin and xyloglucan polymers. A unique aspect is datasets suggesting that enzyme-resistant pectin polymers 'coat' the inner xyloglucan-rich skin cells. This data has important implications for developing effective strategies for efficient release of favorable compounds (pigments, tannins, aromatics, etc.) from the berry tissues during winemaking. This study provides a framework to understand the complex interactions between the grape matrix and carbohydrate-active enzymes to produce wine of desired quality and consistency.

Research paper thumbnail of The resurrection plant, Myrothamnus flabellifolius: one species or many?: classifying plants

Research paper thumbnail of Following the Compositional Changes of Fresh Grape Skin Cell Walls during the Fermentation Process in the Presence and Absence of Maceration Enzymes

Journal of Agricultural and Food Chemistry, 2015

Cell wall profiling technologies were used to follow compositional changes that occurred in the s... more Cell wall profiling technologies were used to follow compositional changes that occurred in the skins of grape berries (from two different ripeness levels) during fermentation and enzyme maceration. Multivariate data analysis showed that the fermentation process yielded cell walls enriched in hemicellulose components because pectin was solubilized (and removed) with a reduction as well as exposure of cell wall proteins usually embedded within the cell wall structure. The addition of enzymes caused even more depectination and the enzymes unravelled the cell walls enabling better access to, and extraction of, all cell wall polymers. Overripe grapes had cell walls that were extensively hydrolysed and depolymerized probably by natural grape tissue ripening enzymes and this enhanced the impact that the maceration enzymes had on the cell wall monosaccharide profile. The combination of the techniques that were used is an effective direct measurement of the hydrolysis actions of maceration enzymes on the cell walls of grape berry skin.

Research paper thumbnail of A Systems-Based Molecular Biology Analysis of Resurrection Plants for Crop and Forage Improvement in Arid Environments

John P. Moore and Jill M. FarrantResurrection plants represent a remarkable group of plants posse... more John P. Moore and Jill M. FarrantResurrection plants represent a remarkable group of plants possessing vegetativetissuecapableofsurvivingwaterlosstoanair-drystate.Manyofthesespeciesgrowinsemiarid and arid countries, and a rich diversity is found in Southern Africa. Wereviewthemechanismsproposedtoexplainhowtheytoleratedesiccation,highlight-ingtheprocessesthatprotectthemfrommetabolicdisruption,oxidativedamage,andmechanicalstressduringdehydration.Alsoreviewedarethemolecularmechanismsassociated with sensing water deficit and activating transcriptional processes asso-ciated with desiccation-induced gene expression in these species. Functional genes,whichencodeprotectivemacromoleculesandenzymes,andthesystemsapproaches(transcriptomics and proteomics) utilized are also discussed. The application ofresurrection plant studies in the molecular engineering of valuable crop plants andpotentially providing new forages is highlighted.17.1IntroductionTheabilityoforganismstosurviveextremedehydration(i.e.,desiccation),referredtoas anhydrobiosis (i.e., life without water), has evolved on multiple occasions in theplant,animal,fungal,andmicrobialkingdoms.Anumberofhigherplants,tracheo-phytes, were found to be capable of tolerating desiccation and so these differentspecies became collectively referred to as “resurrection plants” [1, 2]. The nameresurrectionplantoriginatesfromtheobservationoftheseplantsduringrehydrationand denotes the seemingly miraculous manner by which the leaves and stems of adesiccated resurrection plant unfolds and regreens upon water availability.Desiccation tolerance is generally defined as “the ability to survive drying to, orbelow, the absolute water content of 0.1g H

Research paper thumbnail of An overview of the biology of the desiccation-tolerant resurrection plant Myrothamnus flabellifolia

Annals of botany, 2007

Myrothamnus flabellifolia is unique as the only woody resurrection plant. It is an important plan... more Myrothamnus flabellifolia is unique as the only woody resurrection plant. It is an important plant in southern Africa because of its widespread occurrence and usage in African medicine and traditional culture. Many reports have investigated facets of its biology and the mechanisms associated with its desiccation tolerance. The general biology of the woody resurrection plant Myrothamnus flabellifolia is reviewed. The review focuses on the geography and ecology, systematic placement, evolution, morphology and reproductive ecology of M. flabellifolia as well as the wood anatomy and re-filling mechanism. In addition, the desiccation tolerance, ethnobotanical importance and medicinal properties of the plant are reviewed. Also, future research avenues are suggested, in particular the necessity to research the biogeography and systematics of the species and the role of the polyphenols present, as well as the molecular basis of the plant's desiccation tolerance.

Research paper thumbnail of Towards a systems-based understanding of plant desiccation tolerance

Trends in Plant Science, 2009

Research paper thumbnail of Arabinose-rich polymers as an evolutionary strategy to plasticize resurrection plant cell walls against desiccation

Planta, 2012

A variety of Southern African resurrection plants were surveyed using high-throughput cell wall p... more A variety of Southern African resurrection plants were surveyed using high-throughput cell wall profiling tools. Species evaluated were the dicotyledons, Myrothamnus flabellifolia and Craterostigma plantagineum; the monocotyledons, Xerophyta viscosa, Xerophyta schlecterii, Xerophyta humilis and the resurrection grass Eragrostis nindensis, as well as a pteridophyte, the resurrection fern, Mohria caffrorum. Comparisons were made between hydrated and desiccated leaf and frond material, with respect to cell wall composition and polymer abundance, using monosaccharide composition analysis, FT-IR spectroscopy and comprehensive microarray polymer profiling in combination with multivariate data analysis. The data obtained suggest that three main functional strategies appear to have evolved to prepare plant cell walls for desiccation. Arabinan-rich pectin and arabinogalactan proteins are found in the resurrection fern M. caffrorum and the basal angiosperm M. flabellifolia where they appear to act as 'pectic plasticizers'. Dicotyledons with pectin-rich walls, such as C. plantagineum, seem to use inducible mechanisms which consist of up-regulating wall proteins and osmoprotectants. The hemicellulose-rich walls of the grass-like Xerophyta spp. and the resurrection grass E. nindensis were found to contain highly arabinosylated xylans and arabinogalactan proteins. These data support a general mechanism of 'plasticising' the cell walls of resurrection plants to desiccation and implicate arabinose-rich polymers (pectin-arabinans, arabinogalactan proteins and arabinoxylans) as the major contributors in ensuring flexibility is maintained and rehydration is facilitated in these plants.

Research paper thumbnail of Response of the Leaf Cell Wall to Desiccation in the Resurrection Plant Myrothamnus flabellifolius

Plant Physiology, 2006

The Myrothamnus flabellifolius leaf cell wall and its response to desiccation were investigated u... more The Myrothamnus flabellifolius leaf cell wall and its response to desiccation were investigated using electron microscopic, biochemical, and immunocytochemical techniques. Electron microscopy revealed desiccation-induced cell wall folding in the majority of mesophyll and epidermal cells. Thick-walled vascular tissue and sclerenchymous ribs did not fold and supported the surrounding tissue, thereby limiting the extent of leaf shrinkage and allowing leaf morphology to be rapidly regained upon rehydration. Isolated cell walls from hydrated and desiccated M. flabellifolius leaves were fractionated into their constituent polymers and the resulting fractions were analyzed for monosaccharide content. Significant differences between hydrated and desiccated states were observed in the water-soluble buffer extract, pectin fractions, and the arabinogalactan protein-rich extract. A marked increase in galacturonic acid was found in the alkali-insoluble pectic fraction. Xyloglucan structure was a...