ESKIMO1 Disruption in Arabidopsis Alters Vascular Tissue and Impairs Water Transport

Water economy in agricultural practices is an issue that is being addressed through studies aimed at understanding both plant water-use efficiency (WUE), i.e. biomass produced per water consumed, and responses to water shortage. In the model species Arabidopsis thaliana, the ESKIMO1 (ESK1) gene has been described as involved in freezing, cold and salt tolerance as well as in water economy: esk1 mutants have very low evapo-transpiration rates and high water-use efficiency. In order to establish ESK1 function, detailed characterization of esk1 mutants has been carried out. The stress hormone ABA (abscisic acid) was present at high levels in esk1 compared to wild type, nevertheless, the weak water loss of esk1 was independent of stomata closure through ABA biosynthesis, as combining mutant in this pathway with esk1 led to additive phenotypes. Measurement of root hydraulic conductivity suggests that the esk1 vegetative apparatus suffers water deficit due to a defect in water transport. ESK1 promoter-driven reporter gene expression was observed in xylem and fibers, the vascular tissue responsible for the transport of water and mineral nutrients from the soil to the shoots, via the roots. Moreover, in cross sections of hypocotyls, roots and stems, esk1 xylem vessels were collapsed. Finally, using Fourier-Transform Infrared (FTIR) spectroscopy, severe chemical modifications of xylem cell wall composition were highlighted in the esk1 mutants. Taken together our findings show that ESK1 is necessary for the production of functional xylem vessels, through its implication in the laying down of secondary cell wall components

Metabolic consequences of various fruit-based diets in a generalist insect species

All data & code generated during this study have been deposited in the INRAE dataverse: https://entrepot.recherche.data.gouv.fr/dataset.xhtml?persistentId=doi:10.57745/G4D3PG. The shiny application enabling the exploration and analysis of our complete dataset (PCA, GLM/Elastic Net and associated visualizations) is available here: https://fruitfliesmetabo.shinyapps.io/shiny.International audienceMost phytophagous insect species exhibit a limited diet breadth and specialize on a few or a single host plant. In contrast, some species display a remarkably large diet breadth, with host plants spanning several families and many species. It is unclear, however, whether this phylogenetic generalism is supported by a generic metabolic use of common host chemical compounds ('metabolic generalism') or alternatively by distinct uses of diet-specific compounds ('multi-host metabolic specialism')? Here, we simultaneously investigated the metabolomes of fruit diets and of individuals of a generalist phytophagous species, Drosophila suzukii, that developed on them. The direct comparison of metabolomes of diets and consumers enabled us to disentangle the metabolic fate of common and rarer dietary compounds. We showed that the consumption of biochemically dissimilar diets resulted in a canalized, generic response from generalist individuals, consistent with the metabolic generalism hypothesis. We also showed that many diet-specific metabolites, such as those related to the particular color, odor, or taste of diets, were not metabolized, and rather accumulated in consumer individuals, even when probably detrimental to fitness. As a result, while individuals were mostly similar across diets, the detection of their particular diet was straightforward. Our study thus supports the view that dietary generalism may emerge from a passive, opportunistic use of various resources, contrary to more widespread views of an active role of adaptation in this process. Such a passive stance towards dietary chemicals, probably costly in the short term, might favor the later evolution of new diet specializations

TNT oxidation by Fenton reaction: Reagent ratio effect on kinetics and early stage degradation pathways

International audienceThe removal of TNT from contaminated water can be achieved through advanced oxidation treatment. In the present study, its degradation by Fenton reaction was investigated at laboratory scale. Degradation efficiencies were compared by varying Fenton's reagents concentration and ratios. The parallel monitoring of Fenton's reagents concentrations allowed evidencing hydrogen peroxide or ferrous ion contents as limiting factors for TNT removal. The absolute rate constant of the reaction between TNT and hydroxyl radicals was also determined. TNT by-products corresponding to early stage degradation were identified by LC-ESI-MS and LC-ESI-MS/MS after solid phase pre-concentration. For the first time, formation of 2,4,6-trinitro-cyclohexa-2,4-dienol (uncommon), 2,4,6-trinitrobenzylalcohol, 2,4,6-trinitrobenzaldehyde, and one of the dinitro-hydroxy-benzaldehyde isomers were evidenced. Degradation pathways involving hydroxyl radical attacks resulting in methyl group oxidation, decarboxylation, aromatic ring breakage and hydrolysis, were finally proposed. (C) 2011 Elsevier B.V. All rights reserved

Wood degradation by Fomitiporia mediterranea M. Fischer: Physiologic, metabolomic and proteomic approaches

Fomitiporia mediterranea (Fmed) is one of the main fungal species found in grapevine wood rot, also called “amadou,” one of the most typical symptoms of grapevine trunk disease Esca. This fungus is functionally classified as a white-rot, able to degrade all wood structure polymers, i.e., hemicelluloses, cellulose, and the most recalcitrant component, lignin. Specific enzymes are secreted by the fungus to degrade those components, namely carbohydrate active enzymes for hemicelluloses and cellulose, which can be highly specific for given polysaccharide, and peroxidases, which enable white-rot to degrade lignin, with specificities relating to lignin composition as well. Furthermore, besides polymers, a highly diverse set of metabolites often associated with antifungal activities is found in wood, this set differing among the various wood species. Wood decayers possess the ability to detoxify these specific extractives and this ability could reflect the adaptation of these fungi to their specific environment. The aim of this study is to better understand the molecular mechanisms used by Fmed to degrade wood structure, and in particular its potential adaptation to grapevine wood. To do so, Fmed was cultivated on sawdust from different origins: grapevine, beech, and spruce. Carbon mineralization rate, mass loss, wood structure polymers contents, targeted metabolites (extractives) and secreted proteins were measured. We used the well-known white-rot model Trametes versicolor for comparison. Whereas no significant degradation was observed with spruce, a higher mass loss was measured on Fmed grapevine culture compared to beech culture. Moreover, on both substrates, a simultaneous degradation pattern was demonstrated, and proteomic analysis identified a relative overproduction of oxidoreductases involved in lignin and extractive degradation on grapevine cultures, and only few differences in carbohydrate active enzymes. These results could explain at least partially the adaptation of Fmed to grapevine wood structural composition compared to other wood species, and suggest that other biotic and abiotic factors should be considered to fully understand the potential adaptation of Fmed to its ecological niche. Proteomics data are available via ProteomeXchange with identifier PXD036889

A detailed survey of seed coat flavonoids in developing seeds of Brassica napus L.

Proanthocyanidins (PAs) are seed coat flavonoids that impair the digestibility of Brassica napus meal. Development of low-PA lines is associated with a high-quality meal and with increased contents in oil and proteins, but requires better knowledge of seed flavonoids. Flavonoids in Brassica mature seed are mostly insoluble so that very few qualitative and quantitative data are available yet. In the present study, the profiling of seed coat flavonoids was established in eight black-seeded B. napus genotypes, during seed development when soluble flavonoids were present and predominated over the insoluble forms. Thirteen different flavonoids including (−)-epicatechin, five procyanidins (PCs which are PAs composed of epicatechin oligomers only) and seven flavonols (quercetin-3-O-glucoside, quercetin-dihexoside, isorhamnetin-3-O-glucoside, isorhamnetin-hexoside-sulfate, isorhamnetin-dihexoside, isorhamnetin-sinapoyl-trihexoside and kaempferol-sinapoyl-trihexoside) were identified and quantified using liquid chromatography coupled to electrospray ionization-mass spectrometry (LC−ESI-MSn). These flavonol derivatives were characterized for the first time in the seed coat of B. napus, and isorhamnetin-hexoside-sulfate and isorhamnetin-sinapoyl-trihexoside were newly identified in Brassica spp. High amounts of PCs accumulated in the seed coat, with solvent-soluble polymers of (−)-epicatechin reaching up to 10% of the seed coat weight during seed maturation. In addition, variability for both PC and flavonol contents was observed within the panel of eight black-seeded genotypes. Our results provide new insights into breeding for low-PC B. napus genotypes

Screening of naturally occurring resistance inducers for biocontrol of two wheat leaf diseases: Septoria Tritici Blotch and powdery mildew

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Criblage d’inducteurs de résistance d’origine naturelle pour le biocontrôle de maladies foliaires du blé : étude sur la septoriose et l’oïdium du blé

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Hydroxycinnamic acid amide accumulation and PR-protein encoding gene expressionare major responses of wheat during the early stages of powdery mildew infection

International audienceBlumeria graminis f.sp. tritici (Bgt) is an obligate biotrophic fungal pathogen responsible for powdery mildew in bread wheat (Triticum aestivum L.). During the firststeps of this pathogenic interaction, basal defense mechanisms take place in wheat leaves. We used RT-qPCR and metabolomic approaches to analyze these earlystages of the interaction between Bgt and the moderately susceptible wheat cultivar Pakito. The expression of genes encoding pathogenesis-related (PR) proteins (PR1,PR4, PR5 and PR8), known to target the pathogen, increased during the first 48 hours post-inoculation. Moreover, RT-qPCR and metabolomic analyses pointed out theimportance of the phenylpropanoid pathway in quantitative resistance against Bgt. Among metabolites of this pathway, hydroxycinnamic acid amides containing agmatineand putrescine as amine components accumulated from the second to the fourth day after inoculation. This suggests the involvement of these metabolites in quantitativeresistance via cross-linking processes in cell wall for reinforcement, what is supported by the up-regulation of PAL (phenylalanine ammonia-lyase), PR15 (encoding anoxalate oxidase) and POX (peroxidase) further inoculation. This study increases knowledge on basal resistance in wheat, giving new targets to investigate inducedresistance in wheat towards Bgt

Analysis of defense-related gene expression and leaf metabolome in wheat during the early infection stages of Blumeria graminis f.sp. tritici

International audienceBlumeria graminis f.sp. tritici (Bgt) is an obligate biotrophic fungal pathogen responsible for powdery mildew in bread wheat (Triticum aestivum L.). Upon Bgt infection, the wheat plant activates basal defense mechanisms namely PAMP-triggered immunity (PTI) in the leaves during the first few days. Understanding this early stage of quantitative resistance is crucial for developing new breeding tools and evaluating plant resistance inducers for sustainable agricultural practices. In this sense, we used a combination of transcriptomic and metabolomic approaches to analyze the early steps of the interaction between Bgt and the moderately susceptible wheat cultivar Pakito. Bgt infection resulted in an increasing expression of genes encoding pathogenesis-related proteins (PR-proteins, PR1, PR4, PR5 and PR8), known to target the pathogen, during the first 48 hours post-inoculation. Moreover, RT-qPCR and metabolomic analyses pointed out the importance of the phenylpropanoid pathway in quantitative resistance against Bgt. Among metabolites linked to this pathway, hydroxycinnamic acid amides containing agmatine and putrescine as amine component accumulated from the second to the fourth day after inoculation. This suggests their involvement in quantitative resistance via cross-linking processes in cell wall for reinforcement, what is supported by the up-regulation of PAL (phenylalanine ammonia-lyase), PR15 (encoding an oxalate oxidase) and POX (peroxidase) after inoculation. Finally, pipecolic acid, which is considered as a signal involved in systemic acquired resistance (SAR), accumulated after inoculation. These new insights lead to a better understanding of basal defense in wheat leaves after Bgt infection