PrCYP707A1, an ABA catabolic gene, is a key component of Phelipanche ramosa seed germination in response to the strigolactone analogue GR24

After a conditioning period, seed dormancy in obligate root parasitic plants is released by a chemical stimulus secreted by the roots of host plants. Using Phelipanche ramosa as the model, experiments conducted in this study showed that seeds require a conditioning period of at least 4 d to be receptive to the synthetic germination stimulant GR24. A cDNA-AFLP procedure on seeds revealed 58 transcript-derived fragments (TDFs) whose expression pattern changed upon GR24 treatment. Among the isolated TDFs, two up-regulated sequences corresponded to an abscisic acid (ABA) catabolic gene, PrCYP707A1, encoding an ABA 8\u27-hydroxylase. Using the rapid amplification of cDNA ends method, two full-length cDNAs, PrCYP707A1 and PrCYP707A2, were isolated from seeds. Both genes were always expressed at low levels during conditioning during which an initial decline in ABA levels was recorded. GR24 application after conditioning triggered a strong up-regulation of PrCYP707A1 during the first 18h, followed by an 8-fold decrease in ABA levels detectable 3 d after treatment. In situ hybridization experiments on GR24-treated seeds revealed a specific PrCYP707A1 mRNA accumulation in the cells located between the embryo and the micropyle. Abz-E2A, a specific inhibitor of CYP707A enzymes, significantly impeded seed germination, proving to be a non-competitive antagonist of GR24 with reversible inhibitory activity. These results demonstrate that P. ramosa seed dormancy release relies on ABA catabolism mediated by the GR24-dependent activation of PrCYP707A1. In addition, in situ hybridization corroborates the putative location of cells receptive to the germination stimulants in seeds

Homologie d’évolution de peuplements benthiques soumis aux épandages d’insecticides antisimulidiens

L’utilisation hebdomadaire d’insecticides pour lutter contre les Simulles modifie l’abondance des populations benthiques. Les variations ne sont ni de la même ampleur ni du même signe, selon l’insecticide (Abate, chlorphoxime, B.t.) et les taxons.Parmi les dizaines de rivières savanicoles traitées aux insecticides antisimulidiens, seules quelques unes font l’objet d’une surveillance de la faune non-cible. La problématique de ce travail est de savoir s’il est possible de généraliser à l’ensemble des rivières, les fluctuations d’abondance des populations observées sur une station de référence.Sur la station de référence, l’évolution de l’abondance des populations pour les trois insecticides étudiés est mesurée à l’aide du rapport : R/P = log APTi/log AVT, où log APTi est le logarithme de l’effectif moyen pour la période de traitement à l’insecticide i et où log AVT est le logarithme de l’effectif moyen avant traitement. Pour chaque taxon ainsi que pour la faune totale on obtient donc un rapport Abate, un rapport chlorphoxime et un rapport B.t.Les valeurs de ces rapports obtenus pour la station d’Entomokro, sont ensuite appliquées aux effectifs récoltés avant traitement sur trois autres stations. Les valeurs calculées sont comparées aux valeurs observées dans le cadre de la surveillance des rivières.Pour la faune totale, l’écart entre les valeurs calculées et les valeurs observées est très faible, r = 0,98.L’étude par taxon montre que la prédiction de ce modèle est excellente pour les Caenidae et les Hydropsychidae, bonne pour les Baetidae, les Chironomini, les Tricorythidae et les Orthocladiinae, médiocre pour les Tanypodinae et les Tanytarsini.The weekly utilization of insecticides sprayed by the Onchocerciasis Control Programme to control Simulium damnosum larvae modifies the abundance of the non target benthic populations. These insecticides (B.t., Abate and chlorphoxim) have neither the same toxicity nor the same selectivity for the principal taxa. In consequence, the long-term variations of the abundance of the populations are neither of the same importance nor of the same sign (some of them remain the same or decrease while others increase), according to the product and the taxa. In long term, these variations being mainly the consequence of direct toxicity but also take into account the duration of the life cycles as well as spatial and trophic competitions.In this study, only the saxicolous fauna is taken into account. It has been collected on rocks with the Surber sampler during the low water period (December to March).Among the ten savannah rivers treated with antiblackfly insecticides, only few are the object of a non-target fauna monitoring. The object of this work is to find out if it is possible to generalize to all the rivers, the variations in population abundance observed for an insecticide on a control station.In the reference station, the variation of population abundance for each of the insecticides is calculated by means of the ratio R/P = log APTI/log AVT, where log APTi is the logarithm of the average for the period treated with the i insecticide, and where log AVT is the logarithm of the average before treatment. For each taxa as well as for the total fauna, Abate, chlorphoxim and B.t. ratio were defined.The values of these ratio obtained for the Entomokro station on the Marahoué river in the Ivory Coast are then applied to the data collected before treatment on three rivers or stations (Amou-Oblo on the Amou river in Togo, Asubende on the Pru river in Togo and Danangoro on the Marahoué river in the ivory coast). The calculated values are then compared to the values collected after treatment in the river monitoring programme.In the reference station the ratio of the populations collected before and after treatment are sometimes greater, sometimes lower than unit (when the ratio is greater than unit, it means that there is an increase of the abundance of populations during the Processing period).The ratios are very close to the one for the B.t. which is the less toxic insecticide against the non target fauna, the greatest for the chlorphoxim which is the more toxic product and intermediate for Abate which has an intermediate toxicity. It appears that the more insecticides were estimated to be toxic in gutter tests, the more population abundance differ from the reference ones.For the total fauna, differences between the values calculated ans observed were very low (r = 0,98). For the taxa, the prediction of this model is excellent for Caenidae and Hydropsychidae, good for Baetidae, Chironomini, Tricorythidae and Orthocladiinae, but mediocre for Tanypodinae and Tanytarsini. The authors submit some hypotheses to explain the bad adequation of the model for these two taxa; hypotheses based on taxonomic problems and niche releasing

Typology of susceptibilities of aquatic insect larvae to different larvicides in a tropical environment

Multi-gutter tests are used by the Onchocerciasis Control Programme in West Africa to screen antiblackfly larvicides with reference to non-target aquatic insect larvae. Because the tests are not always conducted under the same environmental conditions, direct comparison of results by the usual methods of data analysis presents some difficulties. The application of reciprocal averaging (correspondence analysis) to data from tests carried out using the same protocol indicates that the test periods have no incidence on the impact in gutter of the larvicides. The analysis also makes it possible to classify the insecticide families according to their degree of general toxicity on fauna. In addition there is no evidence of a uniform effect produced by each insecticide family on the principal taxa

Pêches scientifiques. Peuplements de poissons des écosystèmes estuariens, lagunaires et continentaux d'Afrique de l'Ouest. v1.7. IRD - Institute of Research for Development. Occurrence Dataset

Base de données en ligneno abstrac

Fluctuating asymmetry in fish otoliths and heterozygosity in stressful estuarine environments (West Africa)

Fluctuating asymmetry (FA) is assumed to reflect the developmental instability caused by environmental or genetic stress. Fish otoliths represent a very good tool for investigating the consequence of different effects on FA. Otolith FA analysis, coupled with genetic analysis, has been undertaken on two common West African estuarine species, Ethmalosa fimbriata (EFI) and Sarotherodon melanotheron (SME), in two neighbouring estuaries, in order to highlight the impact of salinity on developmental stability. The Gambia estuary has a normal functioning and the Saloum estuary is inverse (saltier waters in the upper river), reaching extremely high salinities (>100 psu) and constituting severe environmental stress. Five sub-populations of EFI and six of SME were studied along a salinity gradient. The differences between right and left otoliths were estimated with image processing by measuring five dimensions (area, perimeter, diameter, rostrum and posterior radii). Analyses of genetic differentiation at three EPIC and one anonymous nuclear gene loci for EFI and six polymorphic enzymatic loci for SME were carried out to measure the level of heterozygosity. Absolute FA in all otolith traits examined was unaffected by gender but increased significantly with fish size. Size-corrected absolute FA did not show any significant difference among sites differing largely in salinity, although a higher asymmetry in otolith area was recorded in the saltiest site. These findings suggest that otolith asymmetry is a poor indicator of osmotic stress. The individual heterozygosity level did not seem to have an effect on otolith FA for either species, even though a slight correlation appeared with otolith area or perimeter. Otolith FA cannot be considered to be a useful indicator for estimating changes linked with environmental or genetic stress in these estuaries

Impact d'une aire marine protégée sur les activités de pêche : l'exemple de l'AMP de Bamboung (Sénégal)

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Identifying consensus on coastal lagoons ecosystem services and conservation priorities for an effective decision making : a Q approach

Coastal lagoons ecosystems, while representing benefits for the local populations, have been subjected to high anthropogenic pressures for decades. Hence, conservation measures of these ecosystems are urgently needed and should be combined with their sustainable uses. To address these issues, new research avenues for decision support systems have emphasized the role of the assessment of ecosystem services for establishing conservation priorities by avoiding monetarization approaches. These approaches, because they flatten the various values of nature by projecting them on the single monetary dimension, are often rejected by the stakeholders. We undertake a Q analysis to identify levels of consensus and divergence among stakeholders on the prioritization of ecosystem services provided by two French Mediterranean coastal lagoons areas. The results highlighted that there is a strong consensus among categories of stakeholders in the study sites about the paramount importance of regulation and maintenance services. Three groups of stakeholders, each sharing the same points of view regarding ecosystem services conservation, were identified for each study site. As a non-monetary valuation, Q methodology is very instrumental for the new pluralistic approach of decision support by capturing the values expressed by the stakeholders, without triggering a rejection reflex due to the monetarization

Re-oligotrophication trajectories of macrophyte assemblages in Mediterranean coastal lagoons based on 17-year time-series

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