N-glycome profiling of patatins from different potato species of Solanum genus

Biofortification of potato nutrition

BACKGROUND

Potato (Solanum tuberosum L.) is the fourth most important food crop after rice, wheat and maize in the world with the potential to feed the world's population, and potato is a major staple food in many countries. Currently, potato is grown in more than 100 countries and is consumed by more than 1 billion people worldwide, and the global annual output exceeds 300 million tons. With the rapid increase in the global population, potato will play a key role in food supply. These aspects have driven scientists to genetically engineer potato for yield and nutrition improvement.

AIM OF REVIEW

Potato is an excellent source of carbohydrates, rich in vitamins, phenols and minerals. At present, the nutritional fortification of potato has made remarkable progress, and the biomass and nutrient compositions of potato have been significantly improved through agronomic operation and genetic improvement. This review aims to summarize recent advances in the nutritional fortification of potato protein, lipid and vitamin, and provides new insights for future potato research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review comprehensively summarizes the biofortification of potato five nutrients from protein, lipid, starch, vitamin to mineral. Meanwhile, we also discuss the multilayered insights in the prospects of edible potato fruit, vaccines and high-value products synthesis, and diploid potato seeds reproduction.

N-Linked Glycoproteome Analysis of Diosorea alata Tuber Shows Atypical Glycosylation and Indicates Central Role of Glycosylated Proteins in Tuber Maturation

Glycosylation is an important post translational modification in plants. First analysis of N-linked glycosylated proteins of Dioscorea alata using Concanavalin A lectin affinity chromatography enrichment coupled with label free quantification is presented. In total, 114 enriched glycoproteins were detected. Signal P and sub-cellular localization showed 42.2% of proteins to be secretory. These included peroxidases, endochitinases, calreticulin, calnexin, thaumatins and lipid transfer proteins. Gene Ontology and MapMan analysis predicted the enriched glycoproteins to be involved in processes essential for tuber maturation namely: signal transduction, lignification, protein trafficking, endoplasmic reticulum quality control and cell wall remodeling. This was supported by biochemical validation of the essential glycoproteins. Interestingly, out of the two dioscorin isoforms, Dio B was the only N-glycosylated form. In silico analysis showed O-glycosylation sites in the other form, Dio A suggesting its similarity with sporamin, the storage protein of sweet potato. Absence of signal peptide in Dio B and the presence of non-canonical motif hints towards its atypical glycosylation. The analysis revealed that N-glycosylation of Dio B isoform maintains the activities associated with Dioscorin at maturity and provides an overview of protein N-glycosylation, enriching the glycoproteome database of plants especially tubers.

Differentiation of Sialyl Linkages Using a Combination of Alkyl Esterification and Phenylhydrazine Derivatization: Application for N-Glycan Profiling in the Sera of Patients with Lung Cancer

Alterations in oligosaccharides and types of sialic acid (SA) attachments have been associated with different pathological states. Matrix-assisted laser desorption mass spectrometry (MS) is commonly used for glycosylation studies. However, native sialylated glycans are suppressed or not detected during MS experiments. Consequently, different approaches have been employed to neutralize the negative charge of the carboxyl group. In this study, we present the advantage of phenylhydrazine (PHN) labeling for the detection and efficient discrimination of SA linkages when this derivatization follows alkyl esterification. As expected, PHN-labeled sialylated oligosaccharides with the 2,6-linkage type can be easily recognized according to the additional shift in mass corresponding to the presence of a methyl or ethyl group. Surprisingly, oligosaccharides with the 2,3-linked SA residue instead of a lactone were detected carrying the second PHN unit. This was beneficial as no further processing after esterification was needed to stabilize the lactone form. Moreover, during tandem mass experiments, all modified glycans produced favorable fragmentation patterns with a coherent recognition of SA linkages. Although both types of esterification, herein called the EST-PHN approach, provided comparable results, methylation exhibited marginally higher linkage specificity than ethyl esterification. The simplicity and effectiveness of the methodology are demonstrated on the model compound, sialyllactose, and its applicability for biological studies is presented on N-glycan profiling in the sera of lung cancer patients.

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

Patatin primary structural properties and effects on lipid metabolism

Patatin, the major protein found in potatoes, was purified and shows several isoforms. The essential amino acid content of patatin was ashighas 76%, indicating that it is a valuable protein source. Patatin was an O-linked glycoprotein that contained fucose monosaccharides, as well as mannose, rhamnose, glucose, galactose, xylose, and arabinose. Patatin had a fucosylated glycan structural feature, which strongly bound AAL (Aleuria aurantia Leukoagglutinin), a known fucose binding lectin. Moreover, thelipid metabolism regulatory effects of patatin on the fat catabolism, fat absorption, and inhibition of lipase activity were measured after high-fat feeding of zebrafish larvae. Results revealed that 37.0 μg/mL patatin promoted 23% lipid decomposition metabolism. Meanwhile patatin could inhibite lipase activity and fat absorption, whose effects accounted for half that of a positive control drug. Our findings suggest that patatin, a fucosylated glycoprotein, could potentially be used as a naturalactiveconstituent with anti-obesity effects.

Applicability of Phenylhydrazine Labeling for Structural Studies of Fucosylated N-Glycans

Fucosylation is a common modification, and its site in glycans refers to different normal and pathological processes. Despite intensive research, there is still a lack of methods to discriminate unambiguously the fucose position in one-step. In this work, we propose utility of phenylhydrazine (PHN) labeling for structural studies of fucosylated N-glycans by tandem MALDI mass spectrometry (MS) in the positive ion mode. PHN-tag influences the production of specific ion types, and the MS/MS fragmentation pattern provides useful structural information. All types of core fucosylated N-glycans have produced two abundant ions consistent with B- and C-glycosidic cleavages corresponding to the loss of the FucGlcNAcPHN residue with a mass 457 and 441 Da from the parent ions. These types of fragment ions in N-glycans without a core fucose were associated with the loss of the GlcNAcPHN unit (311 and 295 Da), and fucose cleavage followed the loss of the chitobiose residue. Since diagnostic useful cleavages produce peaks with significant intensities, this approach is also beneficial for rapid recognition of antenna from core fucosylation in glycans detected with low abundances. Moreover, in multifucosylated glycans, this type of labeling allows to distinguish how many fucose residues are on the specific antenna and provides additional information on the topology of N-glycans, such as type of antennarity or identification of bisecting moiety. The practical applicability of the approach is demonstrated on the analysis of multifucosylated N-glycans detected with lower abundances in lung cancer samples.

Antifungal and antimicrobial proteins and peptides of potato (Solanum tuberosum L.) tubers and their applications

Potato proteins are well known for their nutritional, emulsifying, foaming, gel forming or antioxidant properties that all make from them valuable protein source for food industry. Antifungal, antimicrobial and also antiviral properties, described for potato proteins in the review, enrich the possibilities of potato protein usage. Potato proteins were divided into patatin, protease inhibitors and fraction of other proteins that also included, besides others, proteins involved in potato defence physiology. All these proteins groups provide proteins and peptides with antifungal and/or antimicrobial actions. Patatins, obtained from cultivars with resistance to Phytophthora infestans, were able to inhibit spore germination of this pathogen. Protease inhibitors represent the structurally heterogeneous group with broad range of antifungal and antimicrobial activities. Potato protease inhibitors I and II reduced the growth of Phytophthora infestans, Rhizoctonia solani and Botrytis cinerea or of the fungi of Fusarium genus. Members of Kunitz family (proteins Potide-G, AFP-J, Potamin-1 or PG-2) were able to inhibit serious pathogens such as Staphylococcus aureus, Listeria monocytogenes, Escherichia coli or Candida albicans. Potato snakins, defensins and pseudothionins are discussed for their ability to inhibit serious potato fungi as well as bacterial pathogens. Potato proteins with the ability to inhibit growth of pathogens were used for developing of pathogen-resistant transgenic plants for crop improvement. Incorporation of potato antifungal and antimicrobial proteins in feed and food products or food packages for elimination of hygienically risk pathogens brings new possibility of potato protein usage.

Advances in the Biology of Seed and Vegetative Storage Proteins Based on Two-Dimensional Electrophoresis Coupled to Mass Spectrometry

Seed storage proteins play a fundamental role in plant reproduction and human nutrition. They accumulate during seed development as reserve material for germination and seedling growth and are a major source of dietary protein for human consumption. Storage proteins encompass multiple isoforms encoded by multi-gene families that undergo abundant glycosylations and phosphorylations. Two-dimensional electrophoresis (2-DE) is a proteomic tool especially suitable for the characterization of storage proteins because of their peculiar characteristics. In particular, storage proteins are soluble multimeric proteins highly represented in the seed proteome that contain polypeptides of molecular mass between 10 and 130 kDa. In addition, high-resolution profiles can be achieved by applying targeted 2-DE protocols. 2-DE coupled with mass spectrometry (MS) has traditionally been the methodology of choice in numerous studies on the biology of storage proteins in a wide diversity of plants. 2-DE-based reference maps have decisively contributed to the current state of our knowledge about storage proteins in multiple key aspects, including identification of isoforms and quantification of their relative abundance, identification of phosphorylated isoforms and assessment of their phosphorylation status, and dynamic changes of isoforms during seed development and germination both qualitatively and quantitatively. These advances have translated into relevant information about meaningful traits in seed breeding such as protein quality, longevity, gluten and allergen content, stress response and antifungal, antibacterial, and insect susceptibility. This review addresses progress on the biology of storage proteins and application areas in seed breeding using 2-DE-based maps.

Current (Food) Allergenic Risk Assessment: Is It Fit for Novel Foods? Status Quo and Identification of Gaps

Food allergies are recognized as a global health concern. In order to protect allergic consumers from severe symptoms, allergenic risk assessment for well-known foods and foods containing genetically modified ingredients is installed. However, population is steadily growing and there is a rising need to provide adequate protein-based foods, including novel sources, not yet used for human consumption. In this context safety issues such as a potential increased allergenic risk need to be assessed before marketing novel food sources. Therefore, the established allergenic risk assessment for genetically modified organisms needs to be re-evaluated for its applicability for risk assessment of novel food proteins. Two different scenarios of allergic sensitization have to be assessed. The first scenario is the presence of already known allergenic structures in novel foods. For this, a comparative assessment can be performed and the range of cross-reactivity can be explored, while in the second scenario allergic reactions are observed toward so far novel allergenic structures and no reference material is available. This review summarizes the current analytical methods for allergenic risk assessment, highlighting the strengths and limitations of each method and discussing the gaps in this assessment that need to be addressed in the near future.

Mass Spectrometric Analysis of N-Glycoforms of Soybean Allergenic Glycoproteins Separated by SDS-PAGE

Glycosylation of many proteins has been revealed to be closely related with food allergies, and screening and structural analysis of related glycoproteins and glycoallergens are essential for studies in this field. Herein, we describe detailed N-glycoform analysis of all glycoprotein fractions of soybean protein isolate (SPI) separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to disclose structural features of the glycan moieties of more soybean glycoproteins. SPI was fractionated by SDS-PAGE, and the generated protein bands were recovered and subjected to in-gel N-glycan release and labeling using a one-pot method newly developed by our group, followed by detailed analysis by electrospray ionization mass spectrometry (ESI-MS) and online hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HILIC-ESI-MS/MS). As a result, we found seven bands mainly containing oligomannose-type glycans; two mainly contain core α1,3-fucosylated glycans, and six have no glycans. This study is the first report that discovers core α1,3-fucosylated N-glycans in bands 1, 2, and 6 and discloses bands 3, 4, 5, and 7 as glycoproteins and their N-glycoforms. Therefore, it can expand our knowledge about soybean protein glycosylation and provide significant structural reference for research of soybean allergens.

Rapid Sample Preparation Methodology for Plant N-Glycan Analysis Using Acid-Stable PNGase H+

The quantification of potentially allergenic carbohydrate motifs of plant and insect glycoproteins is increasingly important in biotechnological and agricultural applications as a result of the use of insect cell-based expression systems and transgenic plants. The need to analyze N-glycan moieties in a highly parallel manner inspired us to develop a quick N-glycan analysis method based on a recently discovered bacterial protein N-glycanase (PNGase H(+)). In contrast to the traditionally used PNGase A, which is isolated from almond seeds and only releases N-glycans from proteolytically derived glycopeptides, the herein implemented PNGase H(+) allows for the release of N-glycans directly from the glycoprotein samples. Because PNGase H(+) is highly active under acidic conditions, the consecutive fluorescence labeling step using 2-aminobenzamide (2AB) can be directly performed in the same mixture used for the enzymatic deglycosylation step. All sample handling and incubation steps can be performed in less than 4 h and are compatible with microwell-plate sampling, without the need for tedious centrifugation, precipitation, or sample-transfer steps. The versatility of this methodology was evaluated by analyzing glycoproteins derived from various plant sources using ultra-performance liquid chromatography (UPLC) analysis and further demonstrated through the activity analysis of four PNGase H(+) mutant variants.