Storage Proteins Accumulation and Aggregation in Developing Wheat Grains

The aggregative properties of wheat grain prolamins are largely responsible for the technological functionalities of the flours and doughs. The ability of wheat prolamins to form a plastic three-dimensional network during the mixing depends to a large extent on their ability to interact. These aggregative properties, which can be evaluated by measuring their molecular weight distribution, are dependent on the polymorphism of the protein subunits present but also on the environmental conditions that are applied during grain development. Much progress has been made in the last 30 years at a genetic level to better understand and/or to favour the interaction properties of the storage proteins. However, these improvements can be strongly limited by environmental conditions. Any modification of the redox status of the grain cells in response to an oxidative stress can lead to a decrease in the degree of association of the prolamins by limiting the protein-protein interactions during the grain desiccation. Considering the current and projected environmental impacts (i.e. climate change with increasing heat stress), it is essential to better understand these phenomena to implement new breeding strategies for a sustainable quality

The Effect of Plant Genotype, Growth Stage, and Mycosphaerella graminicola Strains on the Efficiency and Durability of Wheat-Induced Resistance by Paenibacillus sp. Strain B2

Plant-growth-promoting rhizobacteria are known as potential biofertilizers and plant-resistance inducers. The current work aims to study the durability of the resistance induced as a response to the inoculation of wheat grains with Paenibacillus sp. strain B2 (PB2) and its influence by plant genotype, growth stage, and Mycosphaerella graminicola strain (the causal agent of Septoria tritici blotch or STB). The results of the plate-counting method showed that PB2 has high potential for wheat-root external colonization [>106 colony-forming unit (CFU)/g of root], and the quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated its internal root-colonization capacity on all tested cultivars. However, the colonization seems to be dependent on wheat-growth stage. The durability of PB2-induced resistance (PB2-IR) was tested at the 3-leaf, tillering, and flag-leaf-growth stages. Additionally, the results showed that the PB2-IR is durable and able to protect the flag leaf, the most important leaf layer during grain fill. It conferred a high protection efficiency (55–94%) against four virulent strains of M. graminicola and over 11 wheat cultivars with different resistance levels to STB. Although, PB2-IR is dependent on M. graminicola strains, wheat genotypes and growth stages, its efficiency, under field conditions, at protecting the last wheat-leaf layers was not an influence. However, it showed 71–79% of protection and reached 81–94% in association with half of the recommended dose of Cherokee® fungicide. This may be explained using laboratory results by its direct impact on M. graminicola strains in these leaf layers and by the indirect reduction of the inoculum coming from leaves infected during the earlier growth stages. Gene expression results showed that PB2-IR is correlated to upregulation of genes involved in defense and cell rescue and a priming effect in the basal defense, jasmonic acid signaling, phenylpropanoids and phytoalexins, and reactive oxygen species gene markers. To conclude, PB2 induces a high and durable resistance against M. graminicola under controlled and field conditions. The PB2-IR is a pathogen strain and is plant-growth-stage and genotype dependent. These results highlight the importance of taking into consideration these factors so as to avoid losing the effectiveness of induced resistance under field conditions

Formation des polymères gluténiques du grain de blé tendre (Triticum aestivum L.)

De nombreuses questions sur la formation des polymères gluténiques dans le grain de blé tendre et leur structure finale demeurent sans réponse. Ainsi la présente étude est effectuée pour mieux comprendre la formation et la structure des agrégats gluténiques. Nous nous sommes attachés à préciser les mécanismes de formation des polymères gluténiques durant le développement du grain dans la mesure où ces associations protéiques conditionnent en grande partie la qualité d'utilisation de la farine de blé tendre. En étudiant l'évolution du statut rédox des protéines de réserve au cours du développement du grain il nous a été notamment possible de démontrer que la formation des très hauts polymères est liée à un phénomène d'oxydation des groupements sulfhydryls libres portés par les sous-unités gluténiques. Ce phénomène, favorisé par le rapprochement des structures polymériques au cours de la séshydratation, conduit à l'apparition de nouvelles liaisons disulfures intermoléculaires et se traduit à la fois par une augmentation de la masse moléculaire et une augmentation du degré de compacité des agrégats gluténiques. Nous avons également pu démontrer que le glutathion était capable de se lier de manière prépondérante à la fraction gluténique limitant ainsi ses capacités d'association lors de la dessiccation. Enfin, une étude exploratoire de modélisation moléculaire a été entreprise afin de proposer une démarche méthodologique permettant d'appréhender les capacités d'interaction des sous-unité gluténiques de haut poids moléculaire.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF

PARAFAC analysis of front-face fluorescence data: Absorption and scattering effects assessed by means of Monte Carlo simulations

International audienc

The Effect of Plant Genotype, Growth Stage, and Mycosphaerella graminicola Strains on the Efficiency and Durability of Wheat-Induced Resistance by Paenibacillus sp. Strain B2

International audiencePlant-growth-promoting rhizobacteria are known as potential biofertilizers and plant-resistance inducers. The current work aims to study the durability of the resistance induced as a response to the inoculation of wheat grains with Paenibacillus sp. strain B2 (PB2) and its influence by plant genotype, growth stage, and Mycosphaerella graminicola strain (the causal agent of Septoria tritici blotch or STB). The results of the plate-counting method showed that PB2 has high potential for wheat-root external colonization [>106 colony-forming unit (CFU)/g of root], and the quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated its internal root-colonization capacity on all tested cultivars. However, the colonization seems to be dependent on wheat-growth stage. The durability of PB2-induced resistance (PB2-IR) was tested at the 3-leaf, tillering, and flag-leaf-growth stages. Additionally, the results showed that the PB2-IR is durable and able to protect the flag leaf, the most important leaf layer during grain fill. It conferred a high protection efficiency (55–94%) against four virulent strains of M. graminicola and over 11 wheat cultivars with different resistance levels to STB. Although, PB2-IR is dependent on M. graminicola strains, wheat genotypes and growth stages, its efficiency, under field conditions, at protecting the last wheat-leaf layers was not an influence. However, it showed 71–79% of protection and reached 81–94% in association with half of the recommended dose of Cherokee® fungicide. This may be explained using laboratory results by its direct impact on M. graminicola strains in these leaf layers and by the indirect reduction of the inoculum coming from leaves infected during the earlier growth stages. Gene expression results showed that PB2-IR is correlated to upregulation of genes involved in defense and cell rescue and a priming effect in the basal defense, jasmonic acid signaling, phenylpropanoids and phytoalexins, and reactive oxygen species gene markers. To conclude, PB2 induces a high and durable resistance against M. graminicola under controlled and field conditions. The PB2-IR is a pathogen strain and is plant-growth-stage and genotype dependent. These results highlight the importance of taking into consideration these factors so as to avoid losing the effectiveness of induced resistance under field condition

Bread wheat quality under limiting environmental conditions: II – Rheological properties of Lebanese wheat genotypes

International audienc

Resolution of mixtures of fluorophores in biological media using fluorescence spectroscopy and Monte Carlo simulation

International audienceIn excitation–emission fluorescence spectroscopy, the simultaneousquantitative prediction and qualitative resolution of mixturesof fluorophores using chemometrics is a major challenge becauseof the scattering and reabsorption effects (turbidity) presentedmainly in biomaterials. The measured fluorescence spectra aredistorted by multiple scattering and reabsorption events in thesurrounding medium, thereby diminishing the performance of thecommonly used three-way resolution methods such as parallelfactor (PARAFAC) analysis or multivariate curve resolutionalternatingleast squares (MCR-ALS). In this work we show thatspectral loadings and concentration profiles from model mixturesprovided using PARAFAC and MCR-ALS are severely distorted byreabsorption and scattering phenomena, although both models fitrather well the experimental data in terms of percentage of theexplained variance. The method to correct the fluorescenceexcitation–emission matrix (EEM) consisted in measuring theoptical properties (absorption parameter la , scattering parameterls, and anisotropy factor g) of samples and calculating thecorresponding transfer function by means of the Monte Carlosimulation method. By applying this transfer function to themeasured EEM, it was possible to compensate for reabsorptionand scattering effects and to restore the ideal EEM, i.e., the EEMthat is due only to fluorophores, without distortions from theabsorbers and scatterers that are present. The PARAFAC and MCRALSdecomposition of the resulting ideal EEMs provided spectralloadings and concentration profiles that matched the true profiles

La qualité technologique du blé tendre (effets de la distribution des masses moléculaires des protéines de réserve )

La valorisation de farines de blé tendre pour la meunerie et la boulangerie est définie actuellement par des critères agronomiques, technologiques et biochimiques. Ils sont dépendants de facteurs (variété, lieu et année) et de leurs interactions. Pour des raisons de performance et stabilité au champ et en transformation boulangère, des variétés hybrides de blé tendre ont été analysées pour répondre à ces deux principales demandes de la filière blé tendre. Aussi bien pour la performance que pour la stabilité, la distribution des masses moléculaires (DMM) des protéines de blé a été reliée avec des variables du test de panification et du mixographe. L'écueil de non caractérisation de la DMM des polymères de taille supérieure à la limite d'exclusion stérique d'un support chromatographique a été levé par la mise en place d'une application de fractionnement par flux-force couplée avec un détecteur UV et de diffusion laser. Ainsi des échantillons de farine ont été différenciés selon la DMM des polymères de gluténine ; le dispositif expérimental comportant 5 variétés hybrides et 11 lignées fixées (dont neufs étaient parentales), obtenues sur 16 lieux en deux années. L'héritabilité des caractères a été calculée et est apparue faible pour les variables de DMM des polymères de gluténine. Ceci confirmerait l'hypothèse d'hyper agrégation des polymères de gluténine au cours de la phase de maturation du grain, régie principalement par l'effet lieu. Nos travaux ont permis d'identifier des critères agronomiques, biochimiques et technologiques pour lesquels les variétés hybrides de blé tendre à notre disposition étaient performantes (rendement) et/ou stables (volume de pain, temps de développement du pic au maximum de consistance au mixographe et paramètres de DMM) par rapport à des variétés fixées parentales et témoins. La stabilité du volume de pain a été reliée avec celle de la DMM des polymères de gluténine (R2 compris entre 0.70 et 0.76).Milling and breadmaking end-uses are defining by agronomical, technological and biochemical criterion. Roots of variations are variety, location, year and theirs respective interactions. As for performance as stability, molecular weight distribution (MWD) of wheat proteins are related with mixograph test and breadmaking. Lacks of the characterization of molecular weight distribution for polymer sizes upper than steric exclusion size limit do not exist with the use of field-flow fractination combined with UV and light scattering detectors. This application allowed us to differentiate flours saples for their MWD ; experimental design contained 5 hybrid wheat warieties and 11 cultivars (9 parental) on 8 localisations for 2 years (at different location). Heritability for all criterions was calculated and was small calculated and was small for glutenin polymers MWD. It confirmed polymers hyperagration hypothesis during grain maturation, witch was major influenced by location effect. For performance and stability reasons for yield and end-use quality, hybrid wheat varieties have been analysed to respond at miller and baker industries. Our works identified agronomical, technological and biochemical parameters for witch analysed hybrid flours were performing (yield) and stable (loaf volume, mixograph peak time MWD parameters) comparing with fixed varieties. Loaf volume stability has been related with glutenin polymers MWD stability (R2 between 0.70 et 0.76)RENNES-Agrocampus-CRD (352382323) / SudocSudocFranceF