14 research outputs found
Valorization of treated wastewater in high saline and waterlogging soil by agroforestry species
Impact of grazing on the floristic diversity of arid rangelands in South Tunisia
If the
effects of grazing on plant diversity have been extensively studied in a wide range of ecosystems, effects of
controlled grazing are still largely unknown. Species diversity indices are useful indicators of the sustainability
of collective rangelands in southern Tunisia. In order to determine an optimal management method of
arid rangelands with high heritage value, we examined the respective effects of continuous grazing, moderate
grazing and rest on the plant communityâs diversity. We compared diversity indices of the vegetation
for three levels of grazing pressure (null, moderate and heavy) in the collective rangelands dominated by
Gymnocarpos decander, Hammada schmittiana, Stipagrostis pungens and Anthyllis sericea of Dhahars in
the south-eastern region of Tataouine (Tunisia). Species richness and Simpsonâs diversity tended to decrease
with increased grazing pressure, but the difference was not significant between ungrazed and moderately
grazed rangelands. By contrast, species evenness tended to increase with grazing pressure. Diversity and
vegetation biological spectrum were only slightly affected by controlled grazing. This study demonstrates
the value of this management practice for biodiversity conservationSi les effets du pùturage sur la diversité floristique ont été largement étudiés sur une large gamme d'écosystÚmes, les effets du pùturage contrÎlé restent encore trÚs peu connus. Les indices de diversité spécifique sont des
indicateurs utiles pour l'évaluation de la durabilité des parcours collectifs. En vue de déterminer un mode de gestion optimal des parcours arides à forte valeur patrimoniale du sud tunisien, nous avons examiné les effets respectifs du pùturage continu, modéré et de mise en repos sur la
diversité des communautés végétales. Les indices de diversité de la végétation ont été comparés en fonction de trois niveaux de pression pastorale (nulle, modérée, forte) sur des parcours communautaires à Gymnocarpos decander, Hammada schmittiana, Stipagrostis pungens et Anthyllis sericea
des Dhahars de la région au sud-est de Tataouine (Tunisie). La richesse spécifique et la diversité de Simpson tendent à diminuer quand la pression de pùturage est plus élevée, mais la différence n'est pas significative entre les parcours non ou modérément pùturés. L'équitabilité tend par
contre Ă augmenter avec l'augmentation de la charge animale. La diversitĂ© spĂ©cifique et le spectre biologique de la vĂ©gĂ©tation n'ont Ă©tĂ© que peu affectĂ©s par le pĂąturage contrĂŽlĂ©. Cette Ă©tude montre donc l'intĂ©rĂȘt de ce type de gestion pour la conservation de la biodiversitĂ©
The Phosphate Fast-Responsive Genes <i>PECP1</i> and <i>PPsPase1</i> Affect Phosphocholine and Phosphoethanolamine Content
International audiencePhosphate starvation-mediated induction of the HAD-type phosphatases PPsPase1 (AT1G73010) and PECP1 (AT1G17710) has been reported in Arabidopsis (Arabidopsis thaliana). However, little is known about their in vivo function or impact on plant responses to nutrient deficiency. The preferences of PPsPase1 and PECP1 for different substrates have been studied in vitro but require confirmation in planta. Here, we examined the in vivo function of both enzymes using a reverse genetics approach. We demonstrated that PPsPase1 and PECP1 affect plant phosphocholine and phosphoethanolamine content, but not the pyrophosphate-related phenotypes. These observations suggest that the enzymes play a similar role in planta related to the recycling of polar heads from membrane lipids that is triggered during phosphate starvation. Altering the expression of the genes encoding these enzymes had no effect on lipid composition, possibly due to compensation by other lipid recycling pathways triggered during phosphate starvation. Furthermore, our results indicated that PPsPase1 and PECP1 do not influence phosphate homeostasis, since the inactivation of these genes had no effect on phosphate content or on the induction of molecular markers related to phosphate starvation. A combination of transcriptomics and imaging analyses revealed that PPsPase1 and PECP1 display a highly dynamic expression pattern that closely mirrors the phosphate status. This temporal dynamism, combined with the wide range of induction levels, broad expression, and lack of a direct effect on Pi content and regulation, makes PPsPase1 and PECP1 useful molecular markers of the phosphate starvation response
In vivo characterization of the role of phosphatases family PS2;1 to 3, early markers of phosphate deficiency in Arabidopsis thaliana
Le phosphate (Pi) est un macroĂ©lĂ©ment essentiel au dĂ©veloppement de la plante. Lors d'une carence en Pi, l'expression de plusieurs gĂšnes est dĂ©rĂ©gulĂ©e permettant Ă la plante de s'adapter Ă ce type de stress abiotique. Chez Arabidopsis thaliana, la carence induit trĂšs fortement PS2;1 (At1g73010) et PS2;2 (At1g17710), deux phosphatases de type HAD. La fonction biochimique de ces deux protĂ©ines a Ă©tĂ© caractĂ©risĂ©e prĂ©cĂ©demment in vitro, mais leur rĂŽle in vivo reste Ă Ă©tablir.Dans ce travail de thĂšse, nous avons examinĂ© la fonction in planta de ces deux protĂ©ines en utilisant des approches de gĂ©nĂ©tique inverse. Affecter leur niveau d'expression par surexpression ou inactivation nâa dâeffet ni sur la teneur en Pi de la cellule vĂ©gĂ©tale, ni sur des marqueurs classiques de la carence en Pi. Par contre, nous montrons que PS2;1 et PS2;2 assurent la dĂ©gradation de la phosphocholine et potentiellement la phosphoĂ©thanolamine, deux composĂ©s identifiĂ©s comme substrats potentiels lors des analyses in vitro.Nos donnĂ©es ne suggĂšrent pas dâimplication de PS2;1 et PS2;2 dans la dĂ©gradation du pyrophosphate, un troisiĂšme substrat potentiel proposĂ© suites aux analyses in vitro. Nos rĂ©sultats suggĂšrent que les deux protĂ©ines PS2;1 et PS2;2 interviennent in planta dans le remodelage des lipides membranaires dĂ©clenchĂ©s par la carence en Pi, permettant de convertir les phospholipides en galacto ou sulfolipides. Plus particuliĂšrement, ces enzymes permettraient le recyclage du Pi des tĂȘtes polaires phosphocholine et phosphoĂ©thanolamine, issues de la dĂ©gradation des phospholipides phosphatidylcholine et phosphatidylĂ©thanolaminePhosphate (Pi) is a macroelement essential to plant development. During Pi deficiency, the expression of several genes is deregulated, allowing the plant to cope with this type of abiotic stress. In Arabidopsis thaliana, Pi deficiency strongly induces PS2;1 (At1g73010) and PS2;2 (At1g17710), two HAD-type phosphatases. The biochemical functions of these two proteins were previously characterized in vitro, although their in vivo roles have not yet been established.Here, the functions of these two proteins were examined in plants using reverse genetics approaches. Overexpression or inactivation of their expression levels had no effect on the Pi content of the plant cell, or on classic markers of Pi deficiency. Furthermore, PS2;1 and PS2;2 affect phosphocholine levels in planta (and potentially phosphoethanolamine), two compounds identified as their potential substrates by in vitro assays.In contrast, these findings do not suggest any involvement of PS2;1 or PS2;2 in the degradation of pyrophosphate, another potential substrate according to previous in vitro assays. In conclusion, these results suggest that PS2;1 and PS2;2 are involved in the remodeling of membrane lipids triggered by Pi deficiency, allowing the conversion of phospholipids to galactolipids or sulfolipids. Specifically, these enzymes should allow the recycling of Pi from phosphocholine and phosphoethanolamine polar heads, byproducts of the degradation of phospholipid phosphatidylcholine and phosphatidylethanolamin
Exchange rate regime management in the economic reforms of a small developing economy : the Case of Mauritania
La prĂ©sente thĂšse Ă©tudie le cheminement rĂ©cent de lâĂ©conomie mauritanienne avec un accent particulier sur les volets relatifs aux politiques choisies pour la gestion du rĂ©gime de change. La pĂ©riode concernĂ©e par cette recherche va de lâindĂ©pendance du pays en 1960 jusquâĂ la fin de 2013, annĂ©e au cours de laquelle le pays a mis fin Ă une succession de programmes dâajustement structurel entamĂ©e une vingtaine dâannĂ©es plutĂŽt avec le concours du fonds monĂ©taire international et la banque mondiale. Nous avons montrĂ© les principales Ă©tapes de la politique de change mise en place par les gouvernements successifs avec une tentative dâĂ©valuation des rĂ©sultats obtenus. La recherche apporte â aprĂšs avoir figĂ© les contours thĂ©oriques de la littĂ©rature qui traite du rĂ©gime de change et Ă©tabli une rĂ©trospective sur les choix Ă©conomiques opĂ©rĂ©s par le pays â des Ă©clairages sur la pertinence des approches suivies par les autoritĂ©s pour faire face aux dĂ©fis posĂ©s dans ce domaine. Le travail explique Ă la fois les raisons, et les mĂ©thodes utilisĂ©es par les dirigeants, pour contourner les impĂ©ratifs liĂ©s Ă la gestion Ă©conomique et financiĂšre orthodoxe qui a Ă©tĂ© convenue avec les partenaires au dĂ©veloppement. Ce contournement sâest traduit, entre autres, par des dysfonctionnements importants sur le marchĂ© de change avec la naissance, et le dĂ©veloppement, dâun marchĂ© parallĂšle devenu avec le temps, particuliĂšrement dynamique et important. La thĂšse analyse les consĂ©quences de ce phĂ©nomĂšne et Ă©tudie les circonstances dans lesquelles il a Ă©tĂ© Ă©lucidĂ© et corrigĂ©.This thesis examines the recent progress of the Mauritanian economy with a particular focus on the policy aspects chosen for the management of the exchange rate regime. The period covered by this research ranges from the independence of the country in 1960 to the end of 2013, the year in which the country ended a succession of structural adjustment programs that began around 20 years ago with the support of the International Monetary Fund and the World Bank. We have shown the key steps of the exchange rate policy put in place by successive governments with an attempt to assess the achieved results. The research brings - after having frozen the theoretical outlines of the literature that addresses the exchange rate regime and established a retrospective on the economic choices made by the country - insights into the adequacy of approaches taken by the authorities to face the challenges posed in this domain. The work explains both the reasons and the methods used by leaders to circumvent the imperatives linked to orthodox economic and financial management that has been concluded with development partners. This circumvention has led, among other things, to major dysfunctions in the foreign exchange market with the birth and development of a parallel market that has become particularly dynamic and important over time. The thesis analyzes the consequences of this phenomenon and studies the circumstances in which it has been elucidated and corrected
Variations de la diversité floristique en fonction du mode de gestion des parcours arides de la Tunisie méridionale
The evolution of plant diversity according to three levels of pastoral pressure (null, moderate and strong) was studied in the collective rangelands of Dhahars in the south-eastern region of Tataouine (Tunisia). The study was carried out in the saharian zones in rangelands of Gymnocarpos decander, Hammada schmittiana, Stipagrostis pungens, and Anthyllis sericea. Under moderate grazing species diversity is only slightly affected. The study suggested that moderate grazing might be an effective means to maintain the diversity of the Saharan rangelands because overgrazing resulted in deterioration of this vital resource, which dropped more than 3/4.La variation de la diversitĂ© spĂ©cifique en fonction de trois niveaux de pression pastorale (nulle, modĂ©rĂ©e, forte) a Ă©tĂ© Ă©tudiĂ©e sur des parcours collectifs des Dhahars de la rĂ©gion au sud-est de Tataouine. LâĂ©tude a Ă©tĂ© conduite sur des parcours des zones sahariennes Ă Gymnocarpos decander, Hammada schmittiana, Stipagrostis pungens et Anthyllis sericea.
Sous une pression pastorale modĂ©rĂ©e, la diversitĂ© spĂ©cifique nâest que trĂšs lĂ©gĂšrement affectĂ©e. Ces rĂ©sultats suggĂšrent que le pĂąturage modĂ©rĂ© est un moyen efficace de maintenir la diversitĂ© des parcours sahariens puisque le surpĂąturage a entraĂźnĂ© une dĂ©tĂ©rioration de cette ressource vitale, qui rĂ©gresse de plus de trois quarts.Gamoun Mouldi, Ouled Belgacem Azaiez, Hanchi Belgacem, Neffati Mohamed. Variations de la diversitĂ© floristique en fonction du mode de gestion des parcours arides de la Tunisie mĂ©ridionale. In: Ecologia mediterranea, tome 37 n°2, 2011. NumĂ©ro spĂ©cial, 7e confĂ©rence europĂ©enne SER en Ă©cologie de la restauration, 23-27 aoĂ»t 2010, Avignon, France. pp. 33-44
Effet du pùturage sur la diversité floristique des parcours arides du Sud Tunisien
Impact of grazing on the floristic diversity of arid rangelands in South Tunisia.
If the effects of grazing on plant diversity have been extensively studied in a wide range of ecosystems, effects of controlled grazing are still largely unknown. Species diversity indices are useful indicators of the sustainability of collective rangelands in southern Tunisia. In order to determine an optimal management method of arid rangelands with high heritage value, we examined the respective effects of continuous grazing, moderate grazing and rest on the plant communityâs diversity. We compared diversity indices of the vegetation for three levels of grazing pressure (null, moderate and heavy) in the collective rangelands dominated by Gymnocarpos decander, Hammada schmittiana, Stipagrostis pungens and Anthyllis sericea of Dhahars in the south-eastern region of Tataouine (Tunisia). Species richness and Simpsonâs diversity tended to decrease with increased grazing pressure, but the difference was not significant between ungrazed and moderately grazed rangelands. By contrast, species evenness tended to increase with grazing pressure. Diversity and vegetation biological spectrum were only slightly affected by controlled grazing. This study demonstrates the value of this management practice for biodiversity conservation.Si les effets du pĂąturage sur la diversitĂ© floristique ont Ă©tĂ© largement Ă©tudiĂ©s sur une large gamme dâĂ©cosystĂšmes, les effets du pĂąturage contrĂŽlĂ© restent encore trĂšs peu connus. Les indices de diversitĂ© spĂ©cifique sont des indicateurs utiles pour lâĂ©valuation de la durabilitĂ© des parcours collectifs. En vue de dĂ©terminer un mode de gestion optimal des parcours arides Ă forte valeur patrimoniale du sud tunisien, nous avons examinĂ© les effets respectifs du pĂąturage continu, modĂ©rĂ© et de mise en repos sur la diversitĂ© des communautĂ©s vĂ©gĂ©tales. Les indices de diversitĂ© de la vĂ©gĂ©tation ont Ă©tĂ© comparĂ©s en fonction de trois niveaux de pression pastorale (nulle, modĂ©rĂ©e, forte) sur des parcours communautaires Ă Gymnocarpos decander, Hammada schmittiana, Stipagrostis pungens et Anthyllis sericea des Dhahars de la rĂ©gion au sud-est de Tataouine (Tunisie). La richesse spĂ©cifique et la diversitĂ© de Simpson tendent Ă diminuer quand la pression de pĂąturage est plus Ă©levĂ©e, mais la diffĂ©rence nâest pas significative entre les parcours non ou modĂ©rĂ©ment pĂąturĂ©s. LâĂ©quitabilitĂ© tend par contre Ă augmenter avec lâaugmentation de la charge animale. La diversitĂ© spĂ©cifique et le spectre biologique de la vĂ©gĂ©tation nâont Ă©tĂ© que peu affectĂ©s par le pĂąturage contrĂŽlĂ©. Cette Ă©tude montre donc lâintĂ©rĂȘt de ce type de gestion pour la conservation de la biodiversitĂ©.Gamoun Mouldi, Ouled Belgacem Azaiez, Hanchi Belgacem, Neffati Mohamed, Gillet François. Effet du pĂąturage sur la diversitĂ© floristique des parcours arides du Sud Tunisien. In: Revue d'Ăcologie (La Terre et La Vie), tome 67, n°3, 2012. pp. 271-282
Changes in the Epidemiology of Respiratory Pathogens in Children during the COVID-19 Pandemic
Since the outbreak of the COVID-19 pandemic, a significant decrease in non-COVID-19 respiratory illnesses were observed, suggesting that the implementation of measures against COVID-19 affected the transmission of other respiratory pathogens. The aim of this study was to highlight the changes in the epidemiology of respiratory pathogens in children during the COVID-19 pandemic. All children with Severe Acute respiratory illness admitted to the pediatric departments between January 2018 and December 2021 with negative COVID-19 PCR, were enrolled. The detection of respiratory pathogens was made by the Film Array Respiratory Panel. A total of 902 respiratory specimens were tested. A significantly lower positivity rate during the COVID-19 period was found (p = 0.006), especially in infants under 6 months (p = 0.008). There was a substantial absence of detection of Respiratory Syncytial Virus and Influenza A during the winter season following the outbreak of the pandemic (p < 0.05; p = 0.002 respectively). An inter-seasonal resurgence of Respiratory Syncytial Virus was noted. Human Rhinovirus was detected throughout the year, and more prevalent in winter during COVID-19 (p = 0.0002). These changes could be explained by the impact of the implementation of preventive measures related to the COVID-19 pandemic on the transmission of respiratory pathogens in children
Composition of Aliphatic Hydrocarbons in Tunisian Textile Sludge and Produced Composts as a Function of Sludge Ratio
Plant Nitrate Reductases Regulate Nitric Oxide Production and Nitrogen-Fixing Metabolism During the Medicago truncatulaâSinorhizobium meliloti Symbiosis
Nitrate reductase (NR) is the first enzyme of the nitrogen reduction pathway in plants, leading to the production of ammonia. However, in the nitrogen-fixing symbiosis between legumes and rhizobia, atmospheric nitrogen (N 2) is directly reduced to ammonia by the bacterial nitrogenase, which questions the role of NR in symbiosis. Next to that, NR is the best-characterized source of nitric oxide (NO) in plants, and NO is known to be produced during the symbiosis. In the present study, we first surveyed the three NR genes (MtNR1, MtNR2, and MtNR3) present in the Medicago truncatula genome and addressed their expression, activity, and potential involvement in NO production during the symbiosis between M. truncatula and Sinorhizobium meliloti. Our results show that MtNR1 and MtNR2 gene expression and activity are correlated with NO production throughout the symbiotic process and that MtNR1 is particularly involved in NO production in mature nodules. Moreover, NRs are involved together with the mitochondrial electron transfer chain in NO production throughout the symbiotic process and energy regeneration in N 2-fixing nodules. Using an in vivo NMR spectrometric approach, we show that, in mature nodules, NRs participate also in the regulation of energy state, cytosolic pH, carbon and nitrogen metabolism under both normoxia and hypoxia. These data point to the importance of NR activity for the N 2-fixing symbiosis and provide a first explanation of its role in this process.Développement d'une infrastructure française distribuée pour la métabolomique dédiée à l'innovationMécanismes contrÎlant la transition entre fixation d'azote et sénescence dans les nodosités symbiotiques de légumineuse