Inselbergs: potential conservation areas for plant diversity in the face of anthropization

Faced with the loss of biodiversity, particularly plant diversity, due to anthropogenic pressure, particular ecosystems such as inselbergs can constitute refuge areas. The objective of this study is to determine the conservation potential of plant biodiversity on inselbergs in Burkina Faso. A comparative study was carried out between inselberg’s vegetation and the surrounding plains vegetation. In each of these vegetation types, stratified and random sampling was adopted and data were collected in plots of 900 m² for the woody stratum and 100 m² for the herbaceous stratum. The specific diversity was evaluated through the effective numbers of Hill of order Q = 0; 1; 2. The Hill index does not vary between inselbergs and plains and thus reflects a strong similarity in floristic diversity between the two ecosystems. Sorensen’s similarity coefficient also shows a similarity in terms of floristic composition between inselbergs and surrounding plains. In inselbergs, relict species that have disappeared from the surrounding plains of some phytogeographic sectors occur. The flora of inselbergs is also characterised by indicative species of anthropized ecosystem absence. However, these species are present on the surrounding plains. Indeed, the flora of inselbergs is characterised by 11 endemic species. Inselberg’s vegetation is characterised by unique plant communities such as rock pools and Afrotrilepis pilosa mats. The exploitation and mortality rates of woody plants are significantly higher on the surrounding plains than on the inselbergs. The flora and vegetation of inselbergs show the absence of indicator species of disturbed ecosystems. They present endemic and relict species and stable woody stands. Due to the steep slope, lack of suitable soil for agriculture and sacred status of someones, the inselbergs constitute a refuge for plant species and thus contribute to the conservation of biodiversity like the protected areas

The soil microbiome reduces Striga infection of sorghum by modulation of host-derived signaling molecules and root development

Sorghum bicolor is one of the most important cereals in the world and a staple crop for smallholder famers in sub-Saharan Africa. However approximately 20% of sorghum yield is annually lost on the African continent due to infestation with the root parasitic weed Striga hermonthica. Existing Striga management strategies often show an inconsistent to low efficacy. Hence, novel and integrated approaches are needed as an alternative strategy. Here, we demonstrate that the soil microbiome suppresses Striga infection in sorghum. We associate this suppression with microbiome-mediated induction of root endodermal suberization and aerenchyma formation, and depletion of haustorium inducing factors (HIFs), root exudate compounds that are critical for the initial stages of Striga infection. We further identify microbial taxa associated with reduced Striga infection with concomitant changes in root cellular anatomy and differentiation as well as HIF degradation. Our study describes novel microbiome-mediated mechanisms of Striga suppression, encompassing repression of haustorium formation and induction of physical barriers in the host root tissue. These findings open new avenues to broaden the effectiveness of Striga management practices

Phenylpropanoid metabolism study during flax seed germination

Les graines de lin accumulent des quantités exceptionnelles de sécoisolaricirésinol diglucoside estérifié avec d'autres composés phénoliques dans un polymère (macromolécule de lignanes : LM) de rôle encore méconnu et dont la structure reste à compléter. Cette thèse vise à étudier la remobilisation de la LM au cours de la germination en se basant sur des données métabolomiques des graines et des exsudats de graines acquises par GC-MS et LC-MS. L'étude structurale de la LM native a été réalisée en développant une méthodologie basée sur des hydrolyses basiques ménagées. Les résultats qui en découlent révèlent que la dénomination macromolécule de phénylpropanoïdes (PM) est plus adaptée du fait de la diversité des sous-unités constituant cette macromolécule. Une supplémentation avec de l'acide coumarique marqué au 13C dans les premiers stades de la germination montre une réactivation de différentes voies de biosynthèse des phénylpropanoïdes, dont celle des lignanes mais pas du sécoisolaricirésinol. L'accumulation observée pour ce dernier est due sans doute à la dégradation de la PM. La production des phénylpropanoïdes durant la germination semble être dirigée vers deux voies majeures. D'une part, la néo-synthèse de dérivés de sinapoyl-glucose prépare les plantules à l'exposition au rayonnement UV. D'autre part, les produits de dégradation de la PM sont exsudés dans l'exo-métabolome et jouent probablement un rôle important dans la structuration précoce des communautés microbiennes. Dans des stades plus avancés, le rôle de la PM est repris par la néo-synthèse à partir de photosynthétats de composés phénoliques de même type que ceux présents dans la MP et l'exsudation de ces composés dans l'environnement des plantulesFlax seeds accumulate exceptionally high amounts of secoisolariciresinol diglucoside, esterified to aother phenolic compounds in a polymer (the lignan macromolecule: LM). The role of this LM remains unknown and its structure is not fully characterized up to today. This thesis aims to study the remobilization of the LM phenylpropanoids during germination, based on metabolomic data acquired by GC-MS and LC-MS. The structural study of the LM was performed by the development of a method based on mild alkalic hydrolysis. The results hereof show a high diversity in constituants so that «phenylpropanoid macromolecule (PM )» is a more appropriate name. Feeding germinating seeds with 13C marked p-coumaric acid showed a reactivation of different phenylpropanoid biosynthesis pathways, including the biosynthesis of lignans, with the exception of secoisolariciresinol, which is probably derived from the degradation of the PM. The production of phenylpropanoids during germination seems to be directed into two major ways. On the one hand, the neosynthesis of sinapoyl glucose derivatives prepares the seedlings to exposure to UV light. On the other hand, the degradation products of the PM are exudated to the exo-metabolome and probably play an important role in the early structuration of the spermosphere microbial communities. In later stages, the role of the MP is taken over by photosynthetate derived neosynthesis of phenolic compounds of the same type as those present in the PM and exudation of these phenolics in the environment of the seedling

Spatio-temporal dynamics of land use / land cover in the commune of Dori

Land use / land cover is a fundamental variable for the sustainable management of resources as well as for the study and understanding of environmental phenomena. Nowadays, it has become essential in most mapping and monitoring inventories of environmental phenomena. This study aims to assess the changes affecting land use / land cover in the municipality of Dori. The methodological approach is based on the interpretation of Landsat images from three periods (1995, 2006 and 2015). Cartographic data analysis revealed a decrease in the area of natural formations by 16.86% and an increase in anthropized areas by 80%. The matrix of changes made it possible to observe that the tree steppe underwent a more marked transformation of 6.45% into shrub and grassy steppe; 1.42% in rainfed crops. The conversion of shrub / grassy steppes into mosaics of fields is notably observed with a conversion of 13.77%. The study found that human activities are the main drivers of observed changes in land use and occupation in the study area, but variability in rainfall likely also contributed to these observed changes. The results of this study therefore constitute fundamental elements that will help decision-makers in decision-making for the sustainable management of natural resources

An untargeted liquid chromatography-mass spectrometry-based workflow for the structural characterization of plant polyesters

International audienceCell wall localized heterogeneous polyesters are widespread in land plants. The composition of these polyesters, such as cutin, suberin, or more plant-specific forms such as the flax seed coat lignan macromolecule, can be determined after total hydrolysis of the ester linkages. The main bottleneck in the structural characterization of these macromolecules, however, resides in the determination of the higher order monomer sequences. Partial hydrolysates of the polyesters release a complex mixture of fragments of different lengths, each present in low abundance and therefore are challenging to structurally characterize. Here, a method is presented by which liquid chromatography-mass spectrometry (LC-MS) profiles of such partial hydrolysates are searched for pairs of related fragments. LC-MS peaks that show a mass difference corresponding to the addition of one or more macromolecule monomers were connected in a network. Starting from the lowest molecular weight peaks in the network, the annotation of the connections as the addition of one or more polyester monomers allows the prediction of consecutive and increasingly complex adjacent peaks. Multi-stage MS (MSn) experiments further helped to reject, corroborate, and sometimes refine the structures predicted by the network. As a proof of concept, this procedure was applied to partial hydrolysates of the flax seed coat lignan macromolecule, and allowed to characterize 120 distinct oligo-esters, consisting of up to six monomers, and containing monomers and linkages for which incorporation in the lignan macromolecule had not been described before. These results showed the capacity of the approach to advance the structural elucidation of complex plant polyesters

Etching of the seed cuticle by cold plasma shortens imbibitional leakage in Linum usitatissimum L.

International audiencePre-sowing treatment of seeds with cold plasma, a reactive mixture of charged particles, is an emerging, environmentally friendly method, shown to improve water absorption, germination and seedling growth in many crop species. We studied how plasma affects different structural layers in flax seed coats, and focused on the effects on some of the earliest germination events, directly related to imbibition: solute leakage and mucilage extrusion. We characterized the ultrastructure of flax seed coats using scanning electron microscopy (SEM) and observed mucilage extrusion in situ, using environmental SEM. Time-courses of water uptake and solute leakage during germination were recorded, respectively, by weighing the seeds and semi-quantitative metabolite profiling of the exudates using GC-MS, LC-MS and LC-UV. Plasma treatment perforated the cuticle of flax seeds but did not visibly etch the underlying mucilage secretory cell (MSC) walls. Plasma treated seeds took up more water than untreated seeds during imbibition. Mucilage expansion of untreated seeds detached the distal MSC walls from the radial walls and extrusion occurred, relatively slowly, via sparse cracks in the distal cell wall layer. In plasma treated seeds, mucilage extrusion occurred fast, via rupture of distal cell walls of almost every single MSC, and the junctions between distal and radial MSC walls remained intact. Initially, imbibitional solute leakage was higher in plasma treated seeds but the leakage had quasi stopped after one hour of imbibition. In untreated seeds, the leakage continued amply more than two hours after the start of imbibition. Fragments of the lignan macromolecule, stored in parenchymatous cells under the MCS, were released more abundantly in the spermosphere of plasma treated than untreated flax seeds. It is concluded that plasma treatment etches the cuticle of flax seeds and weakens the underlying MSC cell walls, and that such treatment leads to significantly faster recovery of membranes during imbibition, reducing leakage time in germinating seeds

Metabolite profiling of developing Camelina sativa seeds

International audienceIntroduction Camelina sativa is a Brassicaceae with interesting agronomic potential and is considered an alternative oilseed crop. Currently, Camelina is grown mainly for its seed, which shows a high oil content with an unusual fatty acid profile particularly rich in polyunsaturated fatty acids. Camelina seeds contain other potentially valuable compounds and their composition is now relatively well described. However, little information is available on the accumulation dynamics of these compounds during seed development. Objectives Our aim is to describe the dynamics of metabolites accumulation during C. sativa seed development. Methods After purification by HPLC, the fractions were analyzed by LC-MS and NMR to characterize new compounds. The dynamic of metabolites accumulation during seed development was monitored during 15, 25 and 35 days after flowering, and metabolic profilings were performed by LC-MS and GC-MS. Results This study describes for the first time two compounds (quercetin-5b-O-sinapyl-2 `'-O-apiosyl-3-O-rutinoside and epicatechin-7-O-glucose) that have not previously been identified in the seeds of C. sativa. We also show the accumulation kinetics of various metabolites involved in seed development. These investigations highlight a major reorganization of the metabolome with a depletion of the content of most primary metabolites and a high accumulation of most fatty acids, glucosinolates, flavonoids and sinapic acid derivatives. Conclusion This study resulted in the metabolic profile of C. sativa during seed development and enabled to identify two novel compounds in Camelina seeds

Age-Dependent Metabolic Profiles Unravel the Metabolic Relationships within and between Flax Leaves (Linum usitatissimum)

International audienceFlax for oil seed is a crop of increasing popularity, but its cultivation needs technical improvement. Important agronomic traits such as productivity and resistance to stresses are to be regarded as the result of the combined responses of individual organs and their inter-communication. Ultimately, these responses directly reflect the metabolic profile at the cellular level. Above ground, the complexity of the plant phenotype is governed by leaves at different developmental stages, and their ability to synthesise and exchange metabolites. In this study, the metabolic profile of differently-developed leaves was used firstly to discriminate flax leaf developmental stages, and secondly to analyse the allocation of the metabolites within and between leaves. For this purpose, the concentration of 52 metabolites, both primary and specialized, was followed by gas chromatography (GC-) and liquid chromatography coupled to mass spectrometry (LC-MS) in alternate pairs of flax leaves. On the basis of their metabolic content, three populations of leaves in different growth stages could be distinguished. Primary and specialized metabolites showed characteristic distribution patterns, and compounds similarly evolving with leaf age could be grouped by the aid of the Kohonen self-organising map (SOM) algorithm. Ultimately, visualisation of the correlations between metabolites via hierarchical cluster analysis (HCA) allowed the assessment of the metabolic fluxes characterising different leaf developmental stages, and the investigation of the relationships between primary and specialized metabolites