The Population Structure of Glossina palpalis gambiensis from Island and Continental Locations in Coastal Guinea

Guinea is the country with the highest prevalence of sleeping sickness in West Africa, and we undertook a population genetics analysis there of the most dangerous tsetse fly species of West Africa, Glossina palpalis gambiensis. Our aims were to estimate effective population size and the degree of isolation between coastal sites on the mainland of Guinea (including Dubréka, a highly prevalent sleeping sickness focus) and Loos Islands in order to get the most possible accurate vision of feasibility and sustainability of anti-tsetse strategies of these sites. We found very low migration rates of tsetse between sites except between those situated in the Dubréka area, which seems to contain a widely distributed panmictic tsetse population (i.e. a population where mating occurs at random). Effective population sizes on Loos islands estimated with various techniques all converged to surprisingly small values. These values might be explained by a recent decrease in tsetse numbers on Kassa Island due to bauxite mining activities. But on the other sites, other explanations have to be found, including possible variance in reproductive success. Our genetic results suggest that different control strategies should be advised on the mainland (reduction in tsetse densities, no elimination) compared to the islands (total elimination feasible). This approach could be extended to many areas where vector control of Human and Animal Trypanosomoses is contemplated

Caractérisation des modifications physiologiques et métaboliques induites chez Brassica napus L. par l’apport d’extraits algaux ou d’acides humiques

Rapeseed is characterized by a low nitrogen use efficiency, thus requiring high N fertilization rate to maintain yield. Biostimulant application on this crop could improve its agroenvironmental balance. Seaweed extracts and humic acids are known for their beneficial effects on plant growth and yield. However, despite some physiological effects that have been already l described, only few studies focused on the action of these extracts on transcriptome expression to identify their metabolic targets. A screening procedure of 10 humic acids and 5 seaweed extracts was used to identify one humic acid (AH7) and one seaweed extract (AZAL5) which increased rapeseed growth weight and leaf chlorophyll content. A microarray comparison of treated and non-treated rapeseed transcriptome was associated with enzymatic activity analysis and q-PCR analysis of gene expressions. It revealed that humic acid and seaweed extract presents a global action on rapeseed metabolism (with more than 1000 genes differentially expressed). The effect of plant exposition to AH7 and AZAL5 occurred at short and long term, respectively, through a stimulation of nitrogen and sulphur metabolisms with for the latter an increase that was higher than the one expected from higher growth rate. These effects were associated with massive enhancement of chloroplast number per cell during the first 24 hours of rapeseed exposition to humic acid or seaweed extract. A general discussion of results is then presented before perspectives of this work.Le colza est caractérisé par une faible efficience d’utilisation de l’azote et requiert une fertilisation azotée importante. L’utilisation de substances ayant un rôle biostimulant pourrait constituer une alternative d’amélioration de son bilan agroenvironnemental. Les actions bénéfiques des extraits algaux ou dérivés d’acides humiques ont été décrites sur l’augmentation de production de biomasse et le rendement des plantes. Bien que ces effets aient été largement décrits sur le plan physiologique, aucune étude n’a été réalisée à l’échelle du transcriptome afin de déterminer leurs cibles métaboliques chez les plantes. Dans ce travail, un criblage réalisé à partir de 10 extraits humiques et de 5 extraits algaux à permis d’identifier un acide humique (AH7) et un extrait algal (AZAL5) augmentant la production de biomasse et la teneur foliaire en chlorophylles du colza. Une comparaison par microarray des transcriptomes de colzas traités ou non par ces extraits, couplée à des analyses d’activités enzymatiques et d’expression de gènes par q-PCR a permis de mettre en évidence une action globale des extraits AH7 et AZAL5 sur le métabolisme du colza (expression différentielle de plus de 1000 gènes). Les effets d’une exposition à AH7 et AZAL5 se traduisent à moyen et long termes, respectivement, par une stimulation des nutritions azotée et soufrée avec pour cette dernière, une augmentation supérieure à celle requise par l’augmentation de biomasse. Cette activation des voies d’assimilation est associée à une augmentation massive du nombre de chloroplastes par cellule observée dès les 24 premières heures de contact entre le colza et l’extrait algal ou l’acide humique. Après une discussion générale des résultats, les perspectives de ce travail sont présentées

Caractérisation des modifications physiologiques et métaboliques induites chez Brassica napus L. par l apport d extraits algaux ou d acides humiques (Thèse soutenue sur un ensemble de travaux)

Le colza est caractérisé par une faible efficience d utilisation de l azote et requiert une fertilisation azotée importante. L utilisation de substances ayant un rôle biostimulant pourrait constituer une alternative d amélioration de son bilan agroenvironnemental. Les actions bénéfiques des extraits algaux ou dérivés d acides humiques ont été décrites sur l augmentation de production de biomasse et le rendement des plantes. Bien que ces effets aient été largement décrits sur le plan physiologique, aucune étude n a été réalisée à l échelle du transcriptome afin de déterminer leurs cibles métaboliques chez les plantes. Dans ce travail, un criblage réalisé à partir de 10 extraits humiques et de 5 extraits algaux à permis d identifier un acide humique (AH7) et un extrait algal (AZAL5) augmentant la production de biomasse et la teneur foliaire en chlorophylles du colza. Une comparaison par microarray des transcriptomes de colzas traités ou non par ces extraits, couplée à des analyses d activités enzymatiques et d expression de gènes par q-PCR a permis de mettre en évidence une action globale des extraits AH7 et AZAL5 sur le métabolisme du colza (expression différentielle de plus de 1000 gènes). Les effets d une exposition à AH7 et AZAL5 se traduisent à moyen et long termes, respectivement, par une stimulation des nutritions azotée et soufrée avec pour cette dernière, une augmentation supérieure à celle requise par l augmentation de biomasse. Cette activation des voies d assimilation est associée à une augmentation massive du nombre de chloroplastes par cellule observée dès les 24 premières heures de contact entre le colza et l extrait algal ou l acide humique. Après une discussion générale des résultats, les perspectives de ce travail sont présentées.Rapeseed is characterized by a low nitrogen use efficiency, thus requiring high N fertilization rate to maintain yield. Biostimulant application on this crop could improve its agroenvironmental balance. Seaweed extracts and humic acids are known for their beneficial effects on plant growth and yield. However, despite some physiological effects that have been already l described, only few studies focused on the action of these extracts on transcriptome expression to identify their metabolic targets. A screening procedure of 10 humic acids and 5 seaweed extracts was used to identify one humic acid (AH7) and one seaweed extract (AZAL5) which increased rapeseed growth weight and leaf chlorophyll content. A microarray comparison of treated and non-treated rapeseed transcriptome was associated with enzymatic activity analysis and q-PCR analysis of gene expressions. It revealed that humic acid and seaweed extract presents a global action on rapeseed metabolism (with more than 1000 genes differentially expressed). The effect of plant exposition to AH7 and AZAL5 occurred at short and long term, respectively, through a stimulation of nitrogen and sulphur metabolisms with for the latter an increase that was higher than the one expected from higher growth rate. These effects were associated with massive enhancement of chloroplast number per cell during the first 24 hours of rapeseed exposition to humic acid or seaweed extract. A general discussion of results is then presented before perspectives of this work.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Two biostimulants derived from algae or humic acid induce similar responses in the mineral content and gene expression of winter oilseed rape (<em>Brassica napus</em> L.)

International audienceDifferent strategies, known as crop biofortification, can be used to increase micronutrient concentrations in harvested parts to reduce nutrient deficiencies in the human diet. Apart from fertilization and genetic selection, a more environmentally friendly, less expensive, and more immediate solution could rely on the use of biostimulants derived from natural materials. Two biostimulants, AZAL5 and HA7, which are derived from seaweed and black peat, respectively, have been previously described as promoting growth of Brassica napus and having a substantial effect on gene expression. They were further studied to evaluate their effects on N and S and a wide range of other nutrients (that is, K, Ca, P, Mg, Fe, Na, Mn, B, Si, Cu, and Zn). Providing these two biostimulants in the nutrient solution did not change the mineral supply significantly, but they mostly stimulated root growth and macronutrient uptake (N, S, K, and P) at a level similar to growth. Both biostimulants also stimulate chloroplast division. More surprisingly, they also increased Mg, Mn, Na, and Cu plant concentrations and root-to-shoot translocation of Fe and Zn. These observations were associated with an increased expression of a Cu transporter (COPT2) and NRAMP3, a gene putatively involved in Fe and Zn translocation. Overall, this study showed that specific nutrient balance and transport were stimulated by both biostimulants more significantly than growth, offering new perspectives for biofortification strategies

Hydroponics versus field lysimeter studies of urea, ammonium and nitrate uptake by oilseed rape(Brassica napus L.)

International audienceN-fertilizer use efficiencies are affected by their chemical composition and suffer from potential N-losses by volatilization. In a field lysimeter experiment, N-15-labelled fertilizers were used to follow N uptake by Brassica napus L. and assess N-losses by volatilization. Use of urea with NBPT (urease inhibitor) showed the best efficiency with the lowest N losses (8% of N applied compared with 25% with urea alone). Plants receiving ammonium sulphate, had similar yield achieved through a better N mobilization from vegetative tissues to the seeds, despite a lower N uptake resulting from a higher volatilization (43% of applied N). Amounts of N-15 in the plant were also higher when plants were fertilized with ammonium nitrate but N-losses reached 23% of applied N. In parallel, hydroponic experiments showed a deleterious effect of ammonium and urea on the growth of oilseed rape. This was alleviated by the nitrate supply, which was preferentially taken up. B. napus was also characterized by a very low potential for urea uptake. BnDUR3 and BnAMT1, encoding urea and ammonium transporters, were up-regulated by urea, suggesting that urea-grown plants suffered from nitrogen deficiency. The results also suggested a role for nitrate as a signal for the expression of BnDUR3, in addition to its role as a major nutrient. Overall, the results of the hydroponic study showed that urea itself does not contribute significantly to the N nutrition of oilseed rape. Moreover, it may contribute indirectly since a better use efficiency for urea fertilizer, which was further increased by the application of a urease inhibitor, was observed in the lysimeter study

A physiological and molecular study of the effects of nickel deficiency and phenylphosphorodiamidate (PPD) application on urea metabolism in oilseed rape (Brassica napus L.)

Urea is the major nitrogen (N) form supplied as fertilizer in agriculture. However, urease, a nickel-dependent enzyme, allows plants to use external or internally generated urea as a nitrogen source. Since a urease inhibitor is frequently applied in conjunction with urea fertilizer, the N-metabolism of plants may be affected. The aim of this study was to determine physiological and molecular effects of nickel deficiency and a urease inhibitor on urea uptake and assimilation in oilseed rape. Plants were grown on hydroponic solution with urea as the sole N source under three treatments: plants treated with nickel (+Ni) as a control, without nickel (-Ni) and with nickel and phenylphosphorodiamidate (+Ni+PPD). Urea transport and assimilation were investigated. The results show that Ni-deficiency or PPD supply led to reduced growth and reduced N-15-uptake from urea. This effect was more pronounced in PPD-treated plants, which accumulated high amounts of urea and ammonium. Thus, Ni-deficiency or addition of PPD, limit the availability of N and decreased shoot and root amino acid content. The up-regulation of BnDUR3 in roots indicated that this gene is a component of the stress response to nitrogen-deficiency. A general decline of glutamine synthetase (GS) activity and activation of glutamate dehydrogenase (GDH) and increases in its expression level were observed in control plants. At the same time, in (-N) or (+Ni+PPD) treated plants, no increases in GS or GDH activities and expression level were found. Overall results showed that plants require Ni as a nutrient (while most widely used nutrient solutions are devoid of Ni), whether they are grown with or without a urea supply, and that urease inhibitors may have deleterious effects at least in hydroponic grown oilseed rape

Brassica napus Growth is Promoted by Ascophyllum nodosum (L.) Le Jol. Seaweed Extract: Microarray Analysis and Physiological Characterization of N, C, and S Metabolisms

International audienceDespite its high capacity to take up nitrate from soil, winter rapeseed (Brassica napus) is characterized by a low N recovery in seeds. Thus, to maintain yield, rapeseed requires a high fertilization rate. Increasing nutrient use efficiency in rapeseed by addition of a biostimulant could help improve its agroenvironmental balance. The effects of marine brown seaweed Ascophyllum nodosum on plant growth have been well described physiologically. However, to our knowledge, no study has focused on transcriptomic analyses to determine metabolic targets of these extracts. A preliminary screening of different extracts revealed a significant effect of one of them (AZAL5) on rapeseed root (+102 %) and shoot ( 23 %) growth. Microarray analysis was then used on AZAL5-treated or nontreated plants to characterize changes in gene expression that were further supported by physiological evidence. Stimulation of nitrogen uptake (+21 and +115 % in shoots and roots, respectively) and assimilation was increased in a similar manner to growth, whereas sulfate content (+63 and +133 % in shoots and roots, respectively) was more strongly stimulated leading to sulfate accumulation. Among the identified genes whose expression was affected by AZAL5, MinE, a plastid division regulator, was the most strongly affected. Its effect was supported by microscopic analysis showing an enhancement of chloroplast number per cell and starch content but without a significant difference in net photosynthetic rate. In conclusion, it is suggested that AZAL5, which promotes plant growth and nutrient uptake, could be used as a supplementary tool to improve rapeseed agroenvironmental balance

Microarray analysis of humic acid effects on Brassica napus growth: Involvement of N, C and S metabolisms

International audienceWinter rapeseed (Brassica napus) is characterized by a low N recovery in seeds and requires high rates of fertilization to maintain yield. Its nutrient use efficiency could be improved by addition of a biostimulant such as humic acids whose physiological effects have been described previously in some plant species. However, to our knowledge, no study has focused on transcriptomic analyses to determine metabolic targets of this extract. A preliminary screening of ten humic acids revealed a significant effect of one of them (HA7) on rapeseed root growth. Microarray analysis was then used on HA7-treated or non-treated plants to characterize changes in gene expression that were further supported by physiological evidence. Stimulation of nitrogen uptake (+15% in shoots and +108% in roots) and assimilation was found to be increased in a similar manner to growth while sulfate content (+76% in shoots and +137% in roots) was more strongly stimulated leading to higher sulfate accumulation. In parallel, microscopic analysis showed an enhancement of chloroplast number per cell. It is therefore suggested that HA7, which promotes plant growth and nutrient uptake, could be used as a supplementary tool to improve rapeseed nitrogen use efficiency

Potential direct mechanisms involved in the action of humic substances on plant development

International audienceThe main aim of this communication is to discuss the current knowledge about the potential direct mechanisms that are involved in the beneficial action of humic substances on plant development. To this end, we present and discuss here recent results obtained in our laboratory, along with other findings published by other authors. Finally, we propose a hypothetical whole mechanism for explaining the action of humic substances on plant development. In this schema, we point out those steps that remain unclear

Two Biostimulants Derived from Algae or Humic Acid Induce Similar Responses in the Mineral Content and Gene Expression of Winter Oilseed Rape (Brassica napus L.)

International audienceDifferent strategies, known as crop biofortification, can be used to increase micronutrient concentrations in harvested parts to reduce nutrient deficiencies in the human diet. Apart from fertilization and genetic selection, a more environmentally friendly, less expensive, and more immediate solution could rely on the use of biostimulants derived from natural materials. Two biostimulants, AZAL5 and HA7, which are derived from seaweed and black peat, respectively, have been previously described as promoting growth of Brassica napus and having a substantial effect on gene expression. They were further studied to evaluate their effects on N and S and a wide range of other nutrients (that is, K, Ca, P, Mg, Fe, Na, Mn, B, Si, Cu, and Zn). Providing these two biostimulants in the nutrient solution did not change the mineral supply significantly, but they mostly stimulated root growth and macronutrient uptake (N, S, K, and P) at a level similar to growth. Both biostimulants also stimulate chloroplast division. More surprisingly, they also increased Mg, Mn, Na, and Cu plant concentrations and root-to-shoot translocation of Fe and Zn. These observations were associated with an increased expression of a Cu transporter (COPT2) and NRAMP3, a gene putatively involved in Fe and Zn translocation. Overall, this study showed that specific nutrient balance and transport were stimulated by both biostimulants more significantly than growth, offering new perspectives for biofortification strategies