Open field study of some Zea mays hybrids, lipid compounds and fumonisins accumulation

Lipid molecules are increasingly recognized as signals exchanged by organisms interacting in pathogenic and/or symbiotic ways. Some classes of lipids actively determine the fate of the interactions. Host cuticle/cell wall/membrane components such as sphingolipids and oxylipins may contribute to determining the fate of host–pathogen interactions. In the present field study, we considered the relationship between specific sphingolipids and oxylipins of different hybrids of Zea mays and fumonisin by F. verticillioides, sampling ears at different growth stages from early dough to fully ripe. The amount of total and free fumonisin differed significantly between hybrids and increased significantly with maize ripening. Oxylipins and phytoceramides changed significantly within the hybrids and decreased with kernel maturation, starting from physiological maturity. Although the correlation between fumonisin accumulation and plant lipid profile is certain, the data collected so far cannot define a cause-effect relationship but open up new perspectives. Therefore, the question—“Does fumonisin alter plant lipidome or does plant lipidome modulate fumonisin accumulation?”—is still open

Post Rift Evolution of the Indian Margin of Southern Africa

International audienceThe objective of this study is to discuss the evolution of the South African Plateau along the Indian margin ofSouthern Africa. Since the classical works of A. du Toit and L.C. King and the improvement of thermochronologicalmethods and numerical models, the question of the uplift of South African Plateau was highly debatedwith numerous scenarios: early Cretaceous at time of rifting (Van der Beek et al., J.Geophys.Res., 2002), lateCretaceous (Braun et al., Solid Earth, 2014), late Cenozoic (Burke & Gunnell, Geol.Soc.of America, 2008).Limited attention has been paid on the constraints provided by the offshore stratigraphic record of the surroundingmargins. The objective of our study is to integrate onshore and offshore data (seismic profiles andindustrial wells) to (1) analyse the infill of the whole margin (21S to 31S) from its hinterland to the distal deepwater basin, (2) to constrain and quantify the vertical movements. We discuss the impact on accommodation andsediments partitioning, and their significance on South African Plateau uplift history.1. Sedimentary basins of the Indian margin of Southern Africa are related to the break-up of Gondwanaduring late Jurassic, resulting in rifts and flexural basins. First marine incursions started during early Cretaceoustimes (oldest marine outcropping sediments are of Barremian age 128 Ma). The region developed as a normalcontinental shelf at the Aptian-Albian transition (113 Ma).2. The Cretaceous geological history of the basins is characterized by differential uplift and subsidence of thebasement, controlled by structures inherited from break up. As example, major early Cretaceous depocenters of themargin are located on the north of Save-Limpopo uplift (Forster, Paleogography, Paleoclimatology, Paleoecology,1975) showing an eastward drainage pattern, maybe related to a proto Limpopo drainage. Those observationssuggest that the escarpment bordering the Bushveld depression is an old relief inherited from early Cretaceous.3. Two major uplift events occur during upper Cretaceous along the Kwazulu-Maputaland margin (25.5S to31S). During late Cenomanian (95 Ma) and during late Cretaceous (71-66 Ma). Both events are coeval with amajor tilting and erosion of the upstream part of the margin, river incision and the growth of basin floor fans.4. At first order, the margin shows a retrogradational trend up to a major flooding during mid Eocene time (54Ma), dominated by carbonate sedimentation. A widespread tilt of the margin occur during early Miocene (18Ma) times leading to progradational geometries and the actual high elevation topography of the margin.These results suggest that the South African plateau results from a polyphased uplift history. Most of therelief is inherited from three uplift of the margin, during the continental break-up, during late Cenomanian andduring late Cretaceous. The actual high elevation topography was acquired during a widespread tilting of themargin during late Cenozoic

Bilan "Source to Sink" à l’échelle d’un continent - L’Afrique : Dynamique du manteau et routage sédimentaire

International audienceA source to sink approach was performed at the scale of a continent – Africa - in the frame of the TopoAfrica project, with three main objectives (1) the characterization of the relative importance of deformation (uplift) and climate (precipitation) (2) the quantification of the deformation, its nature and causes, (3) the effect of those deformations on the past African topography and on the sediment routing system. We mainly focused on Western, Central and Austral Africa, characterized by anorogenic relief (plains and plateaus) record of long (several 100 km) to very long (several 1000 km) wavelength deformations, respectively of lithospheric and mantle origin. The sink measurement was based on the seismic stratigraphic analysis of numerous regional seismic lines (from the upstream part of the margin to the abyssal plain) merge of industrial and academic data, calibrated in ages and lithologies on reevaluated wells to get the best possible ages. Volumes measured between successive time-lines, were compacted for a comparison with solid eroded volumes.The source study was performed using dated stepped planation surfaces (etchplains and pediplains) - key morphological features of Africa - mappable at catchments-scale. During Late Paleocene to Middle Eocene times, Africa experienced a very hot and very humid climate leading to the formation of an African-scale weathering surface (etchplain) known as the African Surface. This surface today deformed and preserved as large plains, domes or plateaus, can be used as (1) a marker of the very long wavelength deformations and (2) a reference level to measure eroded volumes since 40 Ma. Some other younger planation surfaces were also mapped of (1) Early Oligocene and (2) Late Miocene ages.(1) Deformation (uplift) is the dominant control of the sediment budget. Climate (precipitation) changes only enhance or inhibit a deformation-controlled flux.(2) The sources of clastic sediments are or closed marginal bulges or far field domes due to mantle dynamics with by-pass (transfer zones) along long-lasting polygenic surfaces located in

Mouvements verticaux post-rift des margesindiennes d’Afrique australe

National audienceL’objectif de cette étude est de discuter de la mise en place duPlateau Sud-Africain en amont des marges transformantes Indiennesd’Afrique Australe. Depuis le développement des méthodesthermochronologiques et des modèles numériques, la cinétique etles mécanismes de mise en place du Plateau Sud-Africain est trèsdébattue.- Les modèles thermochronologiques et numériques d’érosion(e.g. Van der Beek et al., J.Geophys.Res., 2002) suggèrent qu’ils’agirait d’un relief ancien, hérité de la phase de rift au Crétacéinférieur.- Les données thermochronologiques (e.g. Brown et al.,J.Geophys.Res., 2002) mettent en évidence une phased’exhumation rapides au Crétacé (110 - 90 Ma) qui concordeavec une accélération des flux silicoclastiques dans les bassinssédimentaires à mer (e.g. Braun et al., Solid Earth, 2014).- Les études géomorphologiques des surfaces d’aplanissementpréservées à terre, l’interprètent comme un relief hérité de surrectionssuccessives (e.g. King, Univ.NatalPress, 1982) avecune phase majeure de déformation au Cénozoïque (~30 Ma) rattachéeà la mise en place dôme Est-Africain (Burke & Gunnell,Geol.Soc.of America, 2008).Peu d’attention a été portée aux bassins côtiers qui bordent cePlateau. L’objectif ici est (1) de réaliser une analyse stratigraphiquedu remplissage sédimentaire des marges indiennesd’Afrique Australe (21S to 31S) en intégrant des observationsde terrains et des données de subsurface (forages et sismique 2D); (2) de contraindre et quantifier les mouvements verticaux qui affectentcette marge ; (3) de discuter l’impact de ces déformationssur la morphologie de la marge (accomodation, partitionnementsédimentaire entre le plateau continental et le bassin profond)et de leurs implications sur la mise en place du Plateau Sud-Africain.- La mise en place du Plateau Sud-Africain est une histoirepolyphasée avec trois phases de déformations majeures : A labase du Turonien (92 Ma), au Crétacé supérieur (78-65 Ma), àla transition Oligocène-Miocène (23 Ma). L’essentiel du reliefest créé pendant le Crétacé, mais sa topographie est acquise auCénozoïque.- Les bassins côtier enregistrent différents types de déformationsdes marges, e.g. (1) basculement de la marge associé à un basculementdu bassin et la mise en place d’une discordance angulairedans le domaine amont ; (2) surrection horizontale de la margequi se traduit par une chute du niveau marin relatif, une reprise del’érosion continentale (incisons fluviatiles) en amont du bassin etla mise en place de prismes de bas-niveau dans le domaine aval.- L’origine de ces déformations est mal comprise, mais leurlongueur d’onde (×1000 km) suggère une origine mantelliqueet/ou des déformations d’échelle continentale

GROWTH OF THE GREAT ESCARPMENT ACROSS THE INDIAN MARGIN OF SOUTH AFRICA: a couple stratigraphic-geomorphologicstudy

International audienceThe South African Plateau is formed by marginal bulges clustered around an intracontinental basin (the KalahariBasin) with a mean elevation between 1000 and 1400 m. On seaward side, marginal bulges form major escarpmentsthat can reach an elevation up to 3500 m in the Drakensberg area, boundering the high elevation continentfrom a dissected coastal region.The factors controlling escarpment evolution of those high-elevation passive margins are highly debated. On theone hand, geomorphic studies interpret escarpments in term of pulses of uplift and scarp retreat (King, The NatalMonocline, 1982; Partridge & Maud, S.Afr.J.Geol., 1987). On the other hand, thermochronological data andnumerical models of escarpment erosion (Gallagher & Brown, Phil.Trans.R.Soc.Lon., 1999; Van der Beek et al.,J.Geophys.Res., 2002) suggest that escarpments predate the breakup with a minimal escarpment retreat duringpost-rift margin evolution.To answer this question, we studied the Indian margin of South Africa (from Bushveld area to Port-Elizabeth)using sequence stratigraphy analysis of industrial seismic lines and wells. This study is coupled with an analysisof the adjacent landforms, constrained by dated sediments and weathering deposits.The first outcomes of our study are:1. A first uplift during Late Cenomanian (95-90 Ma) created an initial escarpment along the Indian coast.2. A second uplift occurred during the latest Cretaceous to earliest Cenozoïc with a sequential tilting andtruncations of the inner part of the margin followed by the incision of pediments on the seaward side of the initialescarpment,3. A third uplift that occurred during Late Eocene – Early Oligocene and Miocene with the incision of two newgenerations of pediments.These preliminary results suggest that the “Great Escarpment” along the Indian coast of South Africa resultsfrom the stepping of at least four generations of pediments which record the polyphasic uplift history of theSouth African Plateau during the last 100 My

Post-Rift Vertical Movements Of The Southern African Margins - Implications For The South African Plateau Uplift

International audienceThe South African Plateau (SAP) is the world’s largest non-orogenic plateau. It forms a large-scale topographic anomaly which rises from sea level to > 1000 m. Most mechanisms proposed to explain its elevation gain imply mantle processes. The age of the uplift and the different steps of relief growth are still debated. On one hand, a Late Cretaceous uplift is supported both by thermochronological studies and sedimentary flux quantifications. On the other hand, geomorphological studies suggest a Late Cenozoic uplift scenario (<30 Ma). However few attentions were paid to the evolution of the overall geomorphic system, from the upstream erosional system to the downstream depositional system. This study is based on two different approaches: - Onshore, on the mapping and chronology of all the macroforms (weathering surfaces, pediments and pediplains, incised rivers, wave-cut platforms) dated by intersection with the few preserved sediments and the volcanics. - Offshore, on a more classical dataset of seismic lines and petroleum wells, coupled with biostratigraphic revaluations (characterization and dating of vertical movements of the margins - sediment volume measurement). The main result of this study is that the SAP is an old Upper Cretaceous relief (90-70 Ma) reactivated during Oligocene (30-15 Ma) times

MASS TRANSFER BETWEEN THE SOUTH AFRICAN PLATEAU AND THE ADJACENT ATLANTIC MARGIN (NAMIBIA - SOUTH AFRICA) SINCE THE GONDWANA BREAK-UP

International audienceThe South African Plateau (SAP) forms a large - scale topographic anomaly (×1000 km)which rises from sea level to up to 3000 m elevation. Tomographic models suggest that thehigh elevated southern African topography is the expression of a surface upwelling caused byflows in the underlying mantle. However, documenting the surface uplift due to mantle flowsis a major challenge in geology. Here we link onshore landforms (planation surfaces, incisedvalleys) of the SAP to offshore sediment accumulation along the Atlantic margin (from 18°S to38°S), using numerous seismic reflexion profiles, well data and outcrops. We attempt to relatesource and sink analysis in order to solve some first order issues relative to the timing of theexhumation and the growth of the Southern African Plateau.Offshore, we calculate the solid sediment volumes history of the margin for the last 131Ma (i.e. late Hauterivian – today) based on Guillocheau et al. [1] approach. Volumes and accumulationrates were higher during the Upper Cretaceous (335 ×103 km3 at 51.5 ×103 km3/Mafrom 100 to 93.5 Ma, 790 ×103 km3 at 63 ×103 km3/Ma from 93.5 to 81 Ma, and 395 ×103 km3 at26.3 ×103 km3/Ma from 81 to 66 Ma). Volumes and accumulation rates were lower for the LowerCretaceous (73 ×103 km3 at 4 ×103 km3/Ma from 131 to 113 Ma, and 16 ×103 km3 at 12.2 ×103km3/Ma from 113 to 100 Ma) and the Cenozoic (67 ×103 km3 at 1.6 ×103 km3/Ma from 66 to 30Ma, and 92 ×103 km3 at 6.5 ×103 km3/Ma from 30 to 11 Ma, and 35 ×103 km3 at 32 ×103 km3/Ma).Onshore, four generations of landforms were recognised and dated by geometrical relationshipswith volcanism and sediments. The successive growth of these landforms are relatedto uplifts (Guillocheau et al. [2]).• > 80 Ma: two generations of planation surfaces (at least). The oldest one forms thehighest reliefs of the study area, which are preserved as remnant plateaus (Etchplains). Its ageis not known. The younger, form a large - scale pediplain that could be related to the increaseof the sedimentary flux occurring during the Upper Cretaceous (i.e. 100 to 81 Ma), driven by aregional uplift.• 80 - 75 to 70 - 65 Ma: large scale pediplain called the Bushmanland Surface. It canbe related to a strike flexure of the margin (i.e. seaward tilting) recognised offshore from 23°Sto 36°S. Most of the present-day relief was probably created by that time. This is supported bythe decrease of the sedimentary flux which suggests a reorganisation of the interior drainagepattern.• 35 - 25 to 15 - 12 Ma: degradation by river incision of the Bushmanland Surface inresponse to a continental scale uplift (?) and/or change of the climate conditions.These results suggest that the Southern African plateau (SAP) results from a two phasesuplift history: (1) a widespread tilting of the margin during late Cretaceous, (2) continental scaledeformations during the Oligocene. Most of the relief is inherited from the Upper CretaceousReferences:[1] Guillocheau et al. (2012) Basin Res., 24(1), 3-30[2] Guillocheau et al. (2016) accepted Gondwana Res

SINK MEASUREMENT OF THE ZAMBEZI SYSTEM (DELTA TO DEEPSEAFAN): A RECORD OF THE EAST AFRICAN RIFT UPLIFT ANDASSOCIATED CLIMATE CHANGES

International audienceThe Zambezi deltaic system is one of the largest in Africa after the Niger, the Congo and the Nile. Thispassive margin-scale delta is characterized by a topographically and tectonically segmented depositionalprofile studied in the frame of the project PAMELAPassive Margin Exploration Laboratoriesfounded byTOTAL and IFREMER): (1) an upstream 10 km thick deltaic wedge with no gravitary tectonics, (2) theAngoche pounded deep depositional area and (3) the Zambezi deep-sea fan, bounded fromm the Angoche areby a major contouritic drift.The sink measurement was based on the seismic stratigraphic analysis of numerous regional seismiclines (from the upstream part of the margin to the abyssal plain) merge of industrial and academic data,calibrated in ages and lithologies on reevaluated wells to get the best possible ages. Volumes measuredbetween successive time-lines, were compacted for a comparison with solid eroded volumes. Uncertaintieswere calculated (including ages, time-depth conversion law, porosities...) using the VolumeEstimator software.Four main periods of sediments delivery were identified: (1) 94-66 Ma (Turonian-Maastrichtian) firstsilicilastic imput, (2) 66-34 Ma (Paleocene-Eocene) – very low siliciclastic supply, (3) 34-5.5 Ma (Oligocene-Miocene) – second input of siliciclastic sediments and 5.5-0 Ma (Plio-Pleistocene) – sharp increase of thesediment supply.These changes correspond to major deformation and/or climate changes. The reconstruction of theclimate (precipitation) evolution was based on a palynological study along wells of the Zambezi Delta andsummarized as follows: 100 to 90 Masemi-arid, 90 Ma (base Coniacian)sharp increase to very humidconditions up to 40 Ma, 40-30 Ma and 15-11 Ma dryer periods, 30-20 Ma and 11-7 Ma very humid conditionsagain.(1) The 94-66 Ma first siliciclastic sediments supply can be related to the uplift of the South AfricanPlateau and the erosion of the Bushveld reentrant. This can be enhanced after 90 by the sharp increase of thehumidity.(2) The 66-34 Ma period of low siliciclasctic supply is both a period of tectonic stability, very humidconditions and then of intense weathering with carbonate platforms.(3) The 34 Ma second increase of siliciclastic sediments results from an African-scale upliftrelated tomantle dynamics – onset of a mechanical erosion of the Eocene weathering profiles.(4) The sharp increase of sediment supply around 5.5 Ma result from more local processes. They are nomajor climate changes with an amplitude higher than the other Neogene variations. This even is related to amajor change of the drainage pattern of the Zambezi River at time of the initiation of the Malawi Rift

Degradation of aflatoxins by means of laccases from trametes versicolor: An in silico insight

Mycotoxins are secondary metabolites of fungi that contaminate food and feed, and are involved in a series of foodborne illnesses and disorders in humans and animals. The mitigation of mycotoxin content via enzymatic degradation is a strategy to ensure safer food and feed, and to addresstheforthcomingissuesinviewoftheglobaltradeandsustainability. Nevertheless, the search for active enzymes is still challenging and time-consuming. The in silico analysis may strongly support the research by providing the evidence-based hierarchization of enzymes for a rational designofmoreeffectiveexperimentaltrials. Thepresentworkdealtwiththedegradationofaflatoxin B1 andM1 bylaccaseenzymesfromTrametesversicolor. Theenzymes–substrateinteractionforvarious enzymeisoformswasinvestigatedthrough3Dmolecularmodelingtechniques. Structuraldifferences among the isoforms have been pinpointed, which may cause different patterns of interaction between aflatoxin B1 and M1. The possible formation of different products of degradation can be argued accordingly. Moreover, the laccase gamma isoform was identified as the most suitable for protein engineering aimed at ameliorating the substrate specificity. Overall, 3D modeling proved to be an effective analytical tool to assess the enzyme–substrate interaction and provided a solid foothold for supporting the search of degrading enzyme at the early stag

MOUVEMENTS VERTICAUX ET BILANS SEDIMENTAIRES DE MADAGASCAR AUCENOZOÏQUE : ETUDE COUPLEE GEOMORPHOLOGIE/STRATIGRAPHIE SISMIQUE

National audienceL’objectif de ce projet est de comprendre la surrection d’un continent de petite taille, l’île deMadagascar et les bilans d’érosion associés. Il s’inscrit dans le cadre du projet PAssive MarginExploration LAboratory (PAMELA – thèse cofinancée par TOTAL-IFREMER), dans lequel noussouhaitons comprendre l’évolution d’une marge dans son intégralité terre-mer au travers de l’analysedes formes du relief à Madagascar et de l’étude stratigraphique des bassins sédimentaires côtiers deMorondava et Majunga (Madagascar). En effet, les formes du relief résultent d’une histoiregéologique associant des mouvements verticaux de plus ou moins grande longueur d’onde à des processusd’érosion, de transport et d’altération, eux-mêmes intimement liés au climat.Madagascar est une île, constituée d’un haut plateau central culminant entre 1200 et 1800md’altitude en moyenne et qui s’étend du nord au sud sur près de 1600km. Il est limité à l’Est par unescarpement côtier majeur, alors que vers l’Ouest, la transition avec la plaine côtière est marquée par lasuccession de surfaces d’aplanissement (etchplain : surfaces plus ou moins altérées et pédiments).L’essentiel des produits d’érosion de cette surrection sont préservés dans deux marges passives, le bassinde Morondava, à l’Ouest limité par la ride de Davie et se déversant lui-même dans la plaine sousmarinedu Zambèze (océan mozambicain), et au Nord, le bassin de Majunga connecté avec la marge sudde l’océan Somalie.L’étude géomorphologique se fonde sur la cartographie des différentes surfaces d’aplanissementétagées, qui traduisent des chutes successives du niveau de base, du fait de la surrection. Cettecartographie est établie d’après l’étude des MNT à 30 et 90m (SRTM), et à des observations deterrain, couplée à des profils topographiques. Concernant les marges, seuls les puits clés du bassin deMorondava ont été analysés pour l’instant.(1) Les puits offshore montrent une succession de 3 périodes. Une période volcano-clastique (trappsde Madagascar au Crétacé supérieur), suivie d’une gigantesque plate-forme carbonatée sans apportsterrigènes, du Paléocène au Miocène moyen. Le retour de la sédimentation clastique est observé àpartir du Miocène moyen cependant contemporaine de quelques plates-formes carbonatées.(2) Des hauts plateaux centraux à la plaine côtière, 5 surfaces ont été identifiées. La première et plushaute donc est une surface d’altération bauxitique, suivie de 4 surfaces pédimentaires.(3) L’intersection de ces surfaces avec le volcanisme, abondant et bien daté (K/Ar sur roche totale)à Madagascar, et avec les séries sédimentaires des bassins côtiers, permet de contraindre l’âge desmouvements verticaux. Tous ces reliefs sont postérieurs à l’Oligocène supérieur.(4) La surface la plus ancienne a subit une déformation importante et apparait particulièrement “bombée ” dans le paysage malgache, conférant à l’île une forme en dôme caractéristique.(5) L’Eocène dans le bassin de Morondava est caractérisé par des dépôts carbonatés très étendus, du sudde l’ile jusqu’au centre du bassin, au niveau de la Tsiribihina. Ils culminent à près de 900m au Nordestde Tuléar, ce qui traduit, aux corrections eustatiques près, des mouvements verticaux d’une ampleurde 900m au minimum.Les données géomorphologiques montrent que la surrection débute donc au Miocène, ce qui esten accord avec les données de puits qui montrent que les premiers dépôts clastiques n’arrivent pasavant le Miocène moyen, sous réserve d’une meilleure datation. Madagascar est le résultat d’unedéformation de type “ dôme ” qui n’est pas sans rappeler celle des dômes éthiopiens et est-africains(Kenyans), qui sont eux, plus anciens