Wheat amylase/trypsin inhibitors (ATIs) : occurrence, function and health aspects

Amylase/trypsin inhibitors (ATIs) are widely consumed in cereal-based foods and have been implicated in adverse reactions to wheat exposure, such as respiratory and food allergy, and intestinal responses associated with coeliac disease and non-coeliac wheat sensitivity. ATIs occur in multiple isoforms which differ in the amounts present in different types of wheat (including ancient and modern ones). Measuring ATIs and their isoforms is an analytical challenge as is their isolation for use in studies addressing their potential effects on the human body. ATI isoforms differ in their spectrum of bioactive effects in the human gastrointestinal (GI), which may include enzyme inhibition, inflammation and immune responses and of which much is not known. Similarly, although modifications during food processing (exposure to heat, moisture, salt, acid, fermentation) may affect their structure and activity as shown in vitro, it is important to relate these changes to effects that may present in the GI tract. Finally, much of our knowledge of their potential biological effects is based on studies in vitro and in animal models. Validation by human studies using processed foods as commonly consumed is warranted. We conclude that more detailed understanding of these factors may allow the effects of ATIs on human health to be better understood and when possible, to be ameliorated, for example by innovative food processing. We therefore review in short our current knowledge of these proteins, focusing on features which relate to their biological activity and identifying gaps in our knowledge and research priorities.Peer reviewe

Variabilité du protéome des graines de colza en relation avec leur processus de sélection (analyse comparative de quatre lignées quasi isogéniques de colza à teneurs variables en acide érucique et glucosinolates)

Le colza est une plante qui représente un intérêt économique important en France, tant sur le plan alimentaire qu industriel. Afin d éliminer deux composés toxiques de la graine de colza (l acide érucique et les glucosinolates) en vue de son utilisation alimentaire, des schémas de rétrocroisements ont été mis en oeuvre et ont abouti à l obtention de variétés dites 00 entraînant la modification d une partie de la composition protéique de la graine de colza. En effet, celles-ci contiennent majoritairement des protéines de réserve : les globulines 12S (cruciférines) et les albumines 2S (napines) dont la teneur relative (rapport 12S/2S) a été modifiée par le processus de sélection. La diminution du taux de glucosinolates a été réalisée au détriment de la teneur en napines, qui pourtant présentent la composition en acides aminés la plus intéressante sur le plan nutritionnel. L analyse que nous avons menée a eu pour objectif principal d étudier plus en détail l impact de la sélection sur le protéome de la graine de colza. Pour cela, quatre lignées quasi-isogéniques de colza, reflétant le schéma de sélection a été choisie afin de mener une analyse protéomique comparative tout en limitant les variations liées à la variété. Notre matériel d étude contient de nombreux composés interférant avec l électrophorèse bi-dimensionnelle, or cette approche nécessite des extraits protéiques les plus propres et complets possibles aussi bien sur le plan qualitatif que quantitatif. Nous avons donc dans un premier temps optimisé les conditions d extraction et défini les conditions d électrophorèse les plus adaptées à une telle étude. Sur la base de ces conditions, nous avons dans un second temps établi une des deux cartes protéiques de graine de colza disponibles actuellement et regroupant une centaine de protéines. Cette carte a servi de base à la suite de l étude. L analyse comparative des graines de quatre lignées de colza a mis en évidence, comme attendu, une faible variation du protéome inter variétal, nous confortant dans le choix d étudier l impact de la sélection au sein d une lignée quasi isogénique. Les résultats obtenus montrent que le processus de sélection utilisé n a qu un impact limité sur l ensemble de la physiologie de la graine que ce soit au cours du développement ou à maturité. Les spots exprimés différentiellement correspondent principalement à des protéines impliquées dans le métabolisme des glucides et dans les systèmes de défense/détoxification de la graine. Nos résultats montrent également d une part, que les protéines de réserve de type 12S ne sont pas affectées par le processus de sélection et d autre part, que le rapport 12S/2S varie. Ceci nous amène à envisager un impact de la sélection sur la teneur en albumine 2S.Brassica napus (Rapeseed) is a crop of nutritional and industrial importance in France. For consumption uses, conventional breeding schemes were developed to eliminate two toxic compounds (erucic acid and glucosinolates) leading to "double zero" varieties but modifing the protein composition of the seeds too. In fact, these seeds mainly contain storage proteins : 12S globulins (cruciferin) and 2S albumins (napin) whose relative content (ratio 12S/2S) has been shown to be modified by breeding process leading to a decrease of the nutritional value of B. Napus meals. The aim of the present study is to investigate more precisely the impact of breeding on the whole proteome of Brassica napus seeds. To this end, a near isogenic line of four rapeseed varieties, reflecting a conventional breeding process, was used to perform a differential comparative proteomic analysis. Many compounds present in these seeds can interfere with two dimensional gel electrophoresis method. For proteomic analysis using this approach, protein extracts have to be the cleanest and the most qualitatively and quantitatively complete as possible. First of all, we have then optimized the protein extraction procedure and the electrophoretic conditions to perform such study. With these conditions we have, in a second time, established one of the two actually available proteome map of B. Napus seeds. This map of about hundred proteins was used as basis for the following study. This later comparative analysis of mature and immature seeds of four rapeseed varieties show, as expected, only few variations of their proteomes, confirming the good choice of studying the impact of breeding on such near isogenic lines. The results either show that the breeding process has only few effect on the seed physiology at proteome level. The sixty five spots of protein differentially expressed between the varieties, mainly correspond to proteins implicated in sugar metabolism and in plant defense system. Our results point out the fact that 12S seed storage proteins are not affected by the process breeding whereas the 12S/2S ratio does. These observations bring us to hypothesize that breeding affect mostly napins,the second major class of seed storage proteins.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Qualité des protéines de colza: quels acquis?

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Revisiting the cell wall of the wheat endosperm

National audienceThe wheat grain is an important source of food, animal feed and industrial raw material. The grain starchy endosperm is a storage tissue that corresponds approximately to the wheat flour. Cell walls only account for about 3% of the endosperm weight but they are prominent for wheat end-use quality (milling, bread-making) and as dietary fibre, they have a major impact on nutritional quality. The cell wall polysaccharides in the wheat endosperm consist in 70 % feruloylated arabinoxylans (AX) and 20% mixed-linked beta-glucans (MLG) which are deposited in the walls during the grain development. Early works have shown that in addition to these major polysaccharides, cellulose and mannans are also found in minor amounts in the dry grain endosperm. More recently callose and xyloglucans were detected transiently in the developing endosperm. No pectins were ever detected although pectins accumulate in the endosperm of the closely related Brachypodium distachyon. By proteomic analysis of Golgi-enriched fractions obtained from the endosperm of developing wheat we identified glycosyltransferases (GT) belonging to families implicated in the synthesis of xylans, MLG, mannans, xyloglucans and pectins. We therefore decided to further analyse the cell wall composition in the endosperm. Positive signals were obtained for mannans, xyloglucans and several pectin domains (homogalacturonans, rhamnogalacturonans, galactans and arabinans) using specific antibodies and after removing the major polysaccharides. Interestingly, some of the minor polysaccharides accumulate evenly in the whole endosperm while others specifically in specialized cells. The transfer cells in the crease region appeared strongly labelled for galactans, arabinans and xyloglucans. The endosperm cell wall is therefore more complex than once thought. We are generating transgenic wheat to silence several genes potentially involved in the synthesis of these polymers to evaluate their role in the developing grain

The seed nuclear proteome

OPEN ACCESS Cette revue date de 2010 mini review article Repetto, Ombretta : ex UMR LEG 0102, n'a jamais intégré l'UMR Agro Present adress : CRO, IRCCS, Centro di Riferimento Oncologico, Istituto di Ricovero e Cura a Carattere Scientifico - Proteomics Core Facility, Experimental and Clinical Pharmacology, Aviano PN, Italie. BAP GEAPSI CT2International audienceUnderstanding the regulatory networks coordinating seed development will help to manipulate seed traits, such as protein content and seed weight, in order to increase yield and seed nutritional value of important food crops, such as legumes. Because of the cardinal role of the nucleus in gene expression, sub-proteome analyses of nuclei from developing seeds were conducted, taking advantage of the sequences available for model species. In this review, we discuss the strategies used to separate and identify the nuclear proteins at a stage when the seed is preparing for reserve accumulation. We present how these data provide an insight into the complexity and distinctive features of the seed nuclear proteome. We discuss the presence of chromatin-modifying enzymes and proteins that have roles in RNA-directed DNA methylation and which may be involved in modifying genome architecture in preparation for seed filling. Specific features of the seed nuclei at the transition between the stage of cell divisions and that of cell expansion and reserve deposition are described here which may help to manipulate seed quality traits, such as seed weight