Discovery of the biostimulant effect of asparagine and glutamine on plant growth in Arabidopsis thaliana

Protein hydrolysates have gained interest as plant biostimulants due to their positive effects on plant performances. They are mainly composed of amino acids, but there is no evidence of the role of individual of amino acids as biostimulants. In this study we carried out in vitro experiments to monitor the development of Arabidopsis seedlings on amino acid containing media in order to analyze the biostimulant properties of the twenty individual proteinogenic amino acids. We demonstrated that proteinogenic amino acids are not good nitrogen sources as compared to nitrate for plant growth. Biostimulant analyses were based on leaf area measurements as a proxy of plant growth. We developed the Amino Acid Use Efficiency index to quantify the biostimulating effect of individual amino acids in the presence of nitrate. This index allowed us to classify amino acids into three groups, characterized by their inhibiting, neutral, and beneficial effects regarding leaf area. Glutamine and asparagine demonstrated the most significant effects in promoting leaf area in the presence of nitrate supply. The stimulating effect was confirmed by using the L and D enantiomeric forms. Both L-glutamine and L-asparagine stimulated leaf area at low concentrations, emphasizing their biostimulating properties. Our plant growth design and AAUE index pave the way for the identification of other bioactive molecules in protein hydrolysates and for the comparison of biostimulant performances

Transcriptional Regulation of Ribosome Components Are Determined by Stress According to Cellular Compartments in Arabidopsis thaliana

Plants have to coordinate eukaryotic ribosomes (cytoribosomes) and prokaryotic ribosomes (plastoribosomes and mitoribosomes) production to balance cellular protein synthesis in response to environmental variations. We identified 429 genes encoding potential ribosomal proteins (RP) in Arabidopsis thaliana. Because cytoribosome proteins are encoded by small nuclear gene families, plastid RP by nuclear and plastid genes and mitochondrial RP by nuclear and mitochondrial genes, several transcriptional pathways were attempted to control ribosome amounts. Examining two independent genomic expression datasets, we found two groups of RP genes showing very different and specific expression patterns in response to environmental stress. The first group represents the nuclear genes coding for plastid RP whereas the second group is composed of a subset of cytoribosome genes coding for RP isoforms. By contrast, the other cytoribosome genes and mitochondrial RP genes show less constraint in their response to stress conditions. The two subsets of cytoribosome genes code for different RP isoforms. During stress, the response of the intensively regulated subset leads to dramatic variation in ribosome diversity. Most of RP genes have same promoter structure with two motifs at conserved positions. The stress-response of the nuclear genes coding plastid RP is related with the absence of an interstitial telomere motif known as telo box in their promoters. We proposed a model for the “ribosome code” that influences the ribosome biogenesis by three main transcriptional pathways. The first pathway controls the basal program of cytoribosome and mitoribosome biogenesis. The second pathway involves a subset of cytoRP genes that are co-regulated under stress condition. The third independent pathway is devoted to the control of plastoribosome biosynthesis by regulating both nuclear and plastid genes

synthesis of biobased polymers for the development of new alkyd waterborne paints with high performance and low environmental impact

Remises à l’honneur grâce à la récente prise de conscience des enjeux environnementaux et la diminution des ressources pétrolières, les résines alkydes connaissent un essor ces dernières années. En effet le développement de produits plus respectueux de la nature et de l’Homme est devenu une priorité dans le monde d’aujourd’hui. Issues de la polycondensation de matières premières renouvelables, elles s’inscrivent dans une chimie plus durable. Cependant, les peintures alkydes reposent sur un séchage oxydatif lent, contrairement au peintures acryliques dont le séchage est uniquement physique. Ainsi des catalyseurs métalliques toxiques sont nécessaires pour obtenir des temps de séchage raisonnables de moins de 6h. Ces catalyseurs sont potentiellement cancérogènes et soumis au règlement REACH, il convient donc de les remplacer. L’objectif de cette thèse est de s’affranchir de la nécessité d’un séchage oxydatif via l’augmentation des masses molaires des résines.Dans un premier temps, un état de l’art sur les alkydes est présenté. Vient ensuite une étude approfondie de la résine Secoia® 1400, la résine commerciale de Ecoat biosourcée à plus de 85% qui sert d’appui pour les études suivantes. Puis, étude modèle de la résine Secoia® 1400 a été effectuée afin de déterminer le rôle de chacun des constituants présents dans sa formulation complexe. Différents phénomènes mis en jeu lors de la montée en masse des résines ont été investigués. À la suite de ces observations, des modifications du procédé de synthèse ainsi que de nouvelles formulations sont mises en œuvre afin de répondre à la problématique de la thèse. Enfin, un état de l’art de la technologie des alkydes hybrides est présenté.Brought back into the spotlight thanks to the recent awareness of environmental issues and the decrease in petroleum resources, alkyd resins have experienced a boom in recent years. Indeed, the development of products that are more respectful of nature and humans has become a priority in today's world. Resulting from the polycondensation of renewable raw materials, they are part of a more sustainable chemistry. However, alkyd paints rely on slow oxidative drying, unlike acrylic paints which dry only physically. Thus toxic metal catalysts are necessary to obtain reasonable drying times of less than 6 hours. These catalysts are potentially carcinogenic and subject to the REACH regulation, so they should be replaced. The objective of this thesis is to overcome the need for oxidative drying by increasing the molar masses of resins.First, a state of the art on alkyds is presented. This is followed by an in-depth study of Secoia® 1400 resin, Ecoat’s more than 85% bio-based commercial resin which is used as a support for the following studies. Then, model study of the Secoia® 1400 resin was carried out in order to determine the role of each of the constituents present in its complex formulation. Various phenomena brought into play during the rise in mass of resins have been investigated. Following these observations, modifications to the synthesis process as well as new formulations are implemented in order to respond to the problem of the thesis. Finally, a state of the art of hybrid alkyd technology is presented

Le colchique et la colchicine (utilisation thérapeutique et intoxications)

STRASBOURG ILLKIRCH-Pharmacie (672182101) / SudocSudocFranceF

Natural Variation of Arabidopsis Root Architecture Reveals Complementing Adaptive Strategies to Potassium Starvation

Root architecture is a highly plastic and environmentally responsive trait that enables plants to counteract nutrient scarcities with different foraging strategies. In potassium (K) deficiency (low K), seedlings of the Arabidopsis (Arabidopsis thaliana) reference accession Columbia (Col-0) show a strong reduction of lateral root elongation. To date, it is not clear whether this is a direct consequence of the lack of K as an osmoticum or a triggered response to maintain the growth of other organs under limiting conditions. In this study, we made use of natural variation within Arabidopsis to look for novel root architectural responses to low K. A comprehensive set of 14 differentially responding root parameters were quantified in K-starved and K-replete plants. We identified a phenotypic gradient that links two extreme strategies of morphological adaptation to low K arising from a major tradeoff between main root (MR) and lateral root elongation. Accessions adopting strategy I (e. g. Col-0) maintained MR growth but compromised lateral root elongation, whereas strategy II genotypes (e.g. Catania-1) arrested MR elongation in favor of lateral branching. K resupply and histochemical staining resolved the temporal and spatial patterns of these responses. Quantitative trait locus analysis of K-dependent root architectures within a Col-0 3 Catania-1 recombinant inbred line population identified several loci each of which determined a particular subset of root architectural parameters. Our results indicate the existence of genomic hubs in the coordinated control of root growth in stress conditions and provide resources to facilitate the identification of the underlying genes

Hybrid alkyds, the glowing route to reach cutting-edge properties?

International audienceThis review highlights both the various polymers grafted to alkyd resins reported in the literature and the different routes to synthesize these alkyd hybrids. Alkyd resins were discovered in the mid-1920s. Then, they quickly found a prominent place among coatings and paint binders thanks to their numerous advantages such as good heat resistance, excellent gloss, and low cost. Nevertheless, in the 50s, the emergence of new synthetic polymers with better properties (chemical resistance, mechanical and thermal properties) such as epoxy, acrylic or polyurethane, weakened the position of the alkyd resins among coating industry. Nowadays, due to global issues such as health and environmental concerns, research focuses on biobased polymers. Since, alkyd resins are mainly biobased, they have gained increasing attention in the last decade. Nevertheless, the issue of using volatile organic compounds (VOC) and the urge of replacing them, have led to the development of new synthetic routes. Moreover, in order to enhance alkyd properties and bridge the gap with new materials, other polymers such as epoxy, acrylates, polyurethanes or siloxanes were used to form alkyd hybrids. Hence, the different strategies to perform alkyd hybrids are detailed and discussed in this review. Furthermore, composites made with alkyd hybrid matrix are presented. Finally, the perspectives about the future developments of alkyd hybrids and the most promising hybrids are discussed