Regulatory Role of Silicon in Mediating Differential Stress Tolerance Responses in Two Contrasting Tomato Genotypes Under Osmotic Stress

Previous studies have shown the role of silicon (Si) in mitigating the adverse effect of drought stress in different crop species. However, data are lacking on a comparison of drought tolerant and drought sensitive crop cultivars in response to Si nutrition. Therefore, the aim of this study was to elucidate the mechanism (s) by which two contrasting tomato genotypes respond to Si nutrition under osmotic stress condition. Two tomato lines contrasting in their response to drought stress were hydroponically grown under polyethylene glycol (PEG, 6000) and two regimes of Si (0 and 1.5 mM). Metabolite profiling was performed in two lines. Growth and relevant physiological parameters, and expression levels of selected genes were also measured. Si application resulted in improved osmotic stress tolerance in both drought tolerant line LA0147 and drought sensitive line FERUM. In the drought tolerant line, Si enhanced uptake of sulfur (S) and ammonium (NH4+) which led to a significantly higher production of amino acids arginine, methionine, serine, and glycine. While in the drought sensitive line, Si significantly increased production of amino acids proline and GABA which further lowered the level of GSSG to GSH ratio and thus balanced the redox homeostasis under osmotic stress. The higher significant production of amino acids arginine, methionine, GABA, and proline enhanced production of free polyamines putrescine and spermidine and improved osmotic stress tolerance. Therefore, we conclude that Si distinctively regulated osmotic stress tolerance in two contrasting tomato genotypes by differential accumulation of relevant amino acids which eventually led to enhanced polyamine metabolism

Responses of hydroponically grown maize to various urea to ammonium ratios: physiological and molecular data

To date urea and ammonium are two nitrogen (N) forms widely used in agriculture. Due to a low production cost, urea is the N form most applied in agriculture. However, its stability in the soil depends on the activity of microbial ureases, that operate the hydrolysis of urea into ammonium. In the soil ammonium is subjected to fast volatilization in form of ammonia, an environmental N loss that contributes to the atmospheric pollution and impacts on farm economies. Based on these considerations, the optimization of N fertilization is useful in order to maximize N acquired by crops and at the same time limit N losses in the environment. The use of mixed nitrogen forms in cultivated soils allows to have urea and ammonium simultaneously available for the root acquisition after a fertilization event. A combination of different N-sources is known to lead to positive effects on the nutritional status of crops. It is plausible suppose that N acquisition mechanisms in plants might be responsive to N forms available in the root external solution, and therefore indicate a cross connection among different N forms, such as urea and ammonium

From bud formation to flowering: transcriptomic state defines the cherry developmental phases of sweet cherry bud dormancy.

Funder: Centre Mondial de l’Innovation Roullier (FR)BACKGROUND: Bud dormancy is a crucial stage in perennial trees and allows survival over winter to ensure optimal flowering and fruit production. Recent work highlighted physiological and molecular events occurring during bud dormancy in trees. However, they usually examined bud development or bud dormancy in isolation. In this work, we aimed to further explore the global transcriptional changes happening throughout bud development and dormancy onset, progression and release. RESULTS: Using next-generation sequencing and modelling, we conducted an in-depth transcriptomic analysis for all stages of flower buds in several sweet cherry (Prunus avium L.) cultivars that are characterized for their contrasted dates of dormancy release. We find that buds in organogenesis, paradormancy, endodormancy and ecodormancy stages are defined by the expression of genes involved in specific pathways, and these are conserved between different sweet cherry cultivars. In particular, we found that DORMANCY ASSOCIATED MADS-box (DAM), floral identity and organogenesis genes are up-regulated during the pre-dormancy stages while endodormancy is characterized by a complex array of signalling pathways, including cold response genes, ABA and oxidation-reduction processes. After dormancy release, genes associated with global cell activity, division and differentiation are activated during ecodormancy and growth resumption. We then went a step beyond the global transcriptomic analysis and we developed a model based on the transcriptional profiles of just seven genes to accurately predict the main bud dormancy stages. CONCLUSIONS: Overall, this study has allowed us to better understand the transcriptional changes occurring throughout the different phases of flower bud development, from bud formation in the summer to flowering in the following spring. Our work sets the stage for the development of fast and cost effective diagnostic tools to molecularly define the dormancy stages. Such integrative approaches will therefore be extremely useful for a better comprehension of complex phenological processes in many species

Copper-deficiency in Brassica napus induces copper remobilization, molybdenum accumulation and modification of the expression of chloroplastic proteins

During the last 40 years, crop breeding has strongly increased yields but has had adverse effects on the content of micronutrients, such as Fe, Mg, Zn and Cu, in edible products despite their sufficient supply in most soils. This suggests that micronutrient remobilization to edible tissues has been negatively selected. As a consequence, the aim of this work was to quantify the remobilization of Cu in leaves of Brassica napus L. during Cu deficiency and to identify the main metabolic processes that were affected so that improvements can be achieved in the future. While Cu deficiency reduced oilseed rape growth by less than 19% compared to control plants, Cu content in old leaves decreased by 61.4%, thus demonstrating a remobilization process between leaves. Cu deficiency also triggered an increase in Cu transporter expression in roots (COPT2) and leaves (HMA1), and more surprisingly, the induction of the MOT1 gene encoding a molybdenum transporter associated with a strong increase in molybdenum (Mo) uptake. Proteomic analysis of leaves revealed 33 proteins differentially regulated by Cu deficiency, among which more than half were located in chloroplasts. Eleven differentially expressed proteins are known to require Cu for their synthesis and/or activity. Enzymes that were located directly upstream or downstream of Cu-dependent enzymes were also differentially expressed

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Chemical induction of larval metamorphosis of Pecten maximus with a note on the nature of naturally occurring triggering substances

Delayed metamorphosis usually occurs when scallop Pecten maximus (L.) larvae are reared in still water. Metamorphosis rates may be increased by adding aqueous extracts of certain marine red algae, including one [Delesseria sanguinea (Linne) Lamouroux (Delesseriaceae, Rhodomelaceae)] from which various chemical inducers have been isolated. Of these, jacaranone (a simple quinol) is by far the most active component; other components (p-OH phenylacetic acid methyl ester, p-OH benzaldehyde, p-OH benzyl alcohol) are only weak inducers. All are catabolic derivatives of tyrosine. Homogentisic acid (biosynthetically related to jacaranone) and some catecholamines (L-DOPA, epinephrine) can also induce metamorphosis of P. maximus larvae. All these compounds can be transformed into quinones by oxidation. This result, together with literature data, strongly suggests that the true inducer(s) present in the environment might possess a quinone or quinone-like structure, as is the case for jacaranone

Etude de la nutrition uréique et ammoniacale chez le colza (Brassica napus L.) et développement de nouveaux inhibiteurs d uréases et de la nitrification

Le développement de nouveaux fertilisants azotés présentant une efficience nutritionnelle améliorée et respectueux de l environnement, présente un intérêt particulier dans le contexte agricole actuel. Ce travail de thèse s est donc attaché (1) à cribler et à tester l efficacité de nouveaux inhibiteurs d uréases et de la nitrification dans le sol, (2) à étudier l impact d un inhibiteur d uréases sur la physiologie et le métabolisme azoté du colza et (3) à évaluer pour la même espèce, l efficacité de différents types d engrais azotés sur la croissance et la nutrition en conditions hydroponiques et de plein champ, ainsi que leur impact sur l environnement. Les différents criblages réalisés ont permis de sélectionner deux inhibiteurs de la nitrification et deux inhibiteurs d uréases qui présentent des caractéristiques agronomiques intéressantes en terme d hydrosolubilité et d écotoxicité. En hydroponie, la présence d un inhibiteur d uréase ou l absence de nickel dans le milieu de culture pénalisent la croissance et la nutrition azotée du colza. Ce dernier présente cependant une faible capacité d absorption racinaire de l urée, relativement à l ammonium et surtout au nitrate, permettant d émettre l hypothèse, sur la base d éléments moléculaires et biochimiques d un état de carence lors d une alimentation uréique, et d un effet toxique en présence d ammonium. En conditions lysimétriques, l application conjointe d urée et d un inhibiteur d uréases (NPBT) permet cependant d obtenir les meilleurs résultats agro-environnementaux (meilleure efficience d utilisation et volatilisation restreinte) relativement à d autres formulations. L ensemble des résultats est ensuite discuté et plusieurs perspectives de recherche sont finalement proposées.The development of new nitrogen fertilizer with improved nutritional efficiency and minimal impact on the environment is of particular interest in the current context of modern agriculture. The aims of this thesis were to (1) to screen and test the effectiveness of new inhibitors which affect the enzyme urease and the process of nitrification in the soil, (2) to study the impact of a urease inhibitor and the lack of nickel on physiology and nitrogen metabolism in oilseed rape and (3) to evaluate, in hydroponic and field studies, the efficiency of different N fertilizers on yield and to assess their impact on the environment. Screening led to the development of two nitrification and urease inhibitors which showed attractive agronomic characteristics in terms of solubility and ecotoxicity. In hydroponic conditions, growth and nitrogen nutrition of oilseed rape were negatively affected by the presence of a urease inhibitor and by the absence of nickel. The capacity of roots to take up urea was found to be low compared to ammonium, and more specifically, to nitrate uptake. Based on biochemical and molecular data we hypothesise that plants were N deficient when grown on urea while, with ammonium nutrition, plants showed signs of toxicity. However, under lysimetric conditions, simultaneous application of urea and a urease inhibitor showed the best agri-environmental performances (higher fertilizer use efficiency with lower N volatilization) relative to other N fertilizers. Several research perspectives are discussed.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Effet d’un agent hépatoprotecteur naturel sur le fonctionnement hépatique et les performances des chèvres laitières en périodes peripartum

La cétose chez la vache laitière et la toxémie de gestation chez la chèvre sont les principales maladies rencontrées en peripartum, elles sont responsables d’importantes pertes économiques. Ces troubles résultent d’un fort déficit énergétique et d’une demande accrue en glucose. Ils se caractérisent par un dérèglement hépatique, une perte de l’appétit et une diminution de la production laitière (Dann et al., 2005). Pour limiter la prévalence et les impacts économiques des cétoses en élevage de ruminants, le centre R&D du groupe Roullier a sélectionné un coproduit naturel issu de l’industrie agroalimentaire, l’OX23P®, pour ses propriétés hépatoprotectrices. L’objectif de ce travail a été d’évaluer l’efficacité de ce produit sur le fonctionnement hépatique et sur les performances des chèvres laitières atteintes par une toxémie de gestation subclinique expérimentalement induite