Etude de l'adaptation de Bruchus affinisàLathyrus sylvestris: analyse de la mortalité avant l'installation des larves dans les graines

Résumé Bruchus affinis Frölich (Coléoptère, Bruchidae), est une espèce univoltine attirée sélectivement par les fleurs de L. sylvestris, qui constitue l'une des trois plantes dont les larves consomment les graines. Il s'agit d'un insecte typiquement spécialisé à l'exploitation de plantes particulières. Cependant, les femelles distribuent leurs ufs sur les gousses jeunes de L. sylvestris sans tenir compte, ni de leur disponibilité en graines, ni du nombre d'ufs déjà présents, alors que le développement des larves est solitaire. Les larves néonates perforent la gousse et gagnent des ovules. Plusieurs larves peuvent atteindre le même ovule, mais une seule se développe dans la graine en formation. Le nombre d'ufs pondus sur les premières gousses dépasse largement le nombre de graines qui se développeront dans ces gousses. La surabondance d'ufs sur les premières gousses entraîne une forte mortalité.Les déplacements des larves dans les gousses et leur comportement de pénétration dans les graines en croissance ne suppriment pas la compétition intraspécifique larvaire.Aucune adaptation n'ajuste la distribution des ufs et la répartition des larves à l'utilisation optimale des disponibilités en graines. Aucune stratégie adaptative ne limite le gaspillage de progéniture; la spécialisation trophique n'a pas entraîné un comportement reproducteur optimisant l'utilisation des ressources et la survie de la descendance.Bien que la période étudiée corresponde à moins de 10% de la durée du cycle annuel de B. affinis, la très forte mortalité observée entre la ponte et l'installation dans les graines constitue vraisemblablement le facteur-clé des fluctuations annuelles de la population. Les causes de cette mortalité varient d'une station à l'autre, et il est impossible de les hiérarchiser.     

Morphological development of Geissois pruinosa (Cunoniaceae) from seed to adult,and the expression of plesiomorphic characters in seedlings

Marked morphological changes occur during development from young seedlings to adults in Geissois pruinosa. At successive stages, leaves change from simple to trifoliolate and finally to 5-foliolate, palmately compound leaves, the margin of the blades changes from dentate to entire, the venation from craspedodromous to brochidodromous, and the stipules switch at about the 7th level from four free lateral ones per node to two fused intrapetiolar ones. Stems and leaves in young seedlings have sparse, erect hairs, but are glabrous in adults. Scattered and often incomplete information on other Cunoniaceae suggest that differences between seedlings and adults in other genera are generally less pronounced. Some seedling characters of G. pruinosa (including toothed leaflet margins and free lateral stipules) occur in the adult foliage of some of its close relatives (the genera Lamanonia and Pseudoweinmannia and Geissois in Australia) and are plesiomorphic within this clade.     

Towards more equal footing in north–south biodiversity research: European and sub-Saharan viewpoints

Research collaboration between developed countries from the northern hemisphere and developing countries in the southern hemisphere is essential for the understanding and protection of the major proportion of biodiversity located in the tropics. Focusing on the case of sub-Saharan Africa, we here assess the real involvement of northern versus southern contributors, and caution against unequal academic benefit sharing arising from non-commercial biodiversity research that may ultimately hamper sustainable knowledge transfer and long-term biodiversity conservation. We discuss possible drivers that may have led to a business of raw biodiversity data. While we fully support the current efforts to stamp out biopiracy through international biodiversity policies and agreements, we illustrate that such legislative frameworks may further constrain biodiversity research, especially in countries where regulations are poorly streamlined and bureaucracy remains rather inert. We therefore ask for workable solutions towards more equal footing in north–south biodiversity research, and propose a number of steps to transgress the current barriers towards a more fair and equitable sharing of benefits arising from biodiversity research.     

Performance of a semiochemical‐baited autoinoculation device treated with Metarhizium anisopliae for control of Frankliniella occidentalis on French bean in field cages

The performance of an autoinoculation device was evaluated in field cage experiments for control of Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), in French bean, Phaseolus vulgaris L. var. Samantha (Fabaceae). Treatments consisted of a fungus‐treated device with and without semiochemical (Lurem‐TR), and a fungus‐free device as control; the fungus used was Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae). The overall mean number of conidia acquired by a single insect was higher in the fungus‐treated semiochemical‐baited device than in the device without semiochemical: 5.0 ± 0.6 × 10⁴ vs. 2.2 ± 0.4 × 10⁴ conidia per insect. The overall thrips mortality was also higher in the semiochemical‐baited device than in the device without the semiochemical: 59.3 ± 3.9 vs. 41.7 ± 3.5%. Conidial viability was not affected in the M. anisopliae‐treated device without semiochemicals, 7 days after treatment, whereas it was considerably decreased – from 81.0 ± 1.3 to 6.5 ± 1.1%, 2 and 7 days post‐inoculation – in the M. anisopliae‐treated semiochemical‐baited device. Thrips mortality was positively correlated with M. anisopliae conidial viability, and conidial viability was negatively correlated with conidial acquisition. This suggests that the semiochemical volatiles reduced the conidial viability, which in turn resulted in significant reduction in thrips mortality, despite the highest conidial acquisition in the semiochemical‐baited fungus‐treated device. Thrips density per plant was significantly reduced in both fungus‐treated treatments (with semiochemical: 8.7 ± 1.7 adults per plant; without semiochemical: 6.6 ± 1.4 adults per plant) compared with the fungus‐free control (19.8 ± 2.6 adults per plant). These results demonstrate the potential for an autoinoculation device strategy for the control of thrips, particularly in screenhouses.     

Phylogenetic diversity of indigenous cowpea bradyrhizobia from soils in Japan based on sequence analysis of the 16S-23S rRNA internal transcribed spacer (ITS) region

Cowpea [Vigna unguiculata (L.) Walp.] is an important legume crop and yet its rhizobia have not been well characterized in many areas. In the present study, sequence analysis of the bacterial 16S-23S rRNA internal transcribed spacer (ITS) region was performed to characterize genetically 76 indigenous cowpea rhizobia from five different geographic regions (Okinawa, Miyazaki, Kyoto, Fukushima and Hokkaido) of Japan. The sequence analysis clustered all isolates in the genus Bradyrhizobium. They were conspecific with B. japonicum, B. yuanmingense, B. elkanii and Bradyrhizobium sp., although none of them grouped with B. liaoningense, B. canariense, B. betae or B. iriomotense. B. yuanmingense was only isolated from the southern region (Okinawa) where it achieved the highest frequency of 69%. B. japonicum was predominant at Miyazaki, Fukushima and Hokkaido with more than 60% of the isolates. B. elkanii was mainly recorded in the southern (Okinawa: 31%, Miyazaki: 33%) and middle (Kyoto: 33%) regions. This species was present at a very low frequency in Fukushima and absent in Hokkaido in the northern area. Bradyrhizobium sp. like-strains were absent in the southern part (Okinawa, Miyazaki) but were concentrated either in the middle regions with 67% of Kyoto isolates and 28% of Fukushima isolates, and in the northern region with 40% of the Hokkaido isolates. This study revealed a geographical distribution of cowpea bradyrhizobia which seemed to be related to the differences in the environmental characteristics (soil type and soil pH, temperature, climate, moisture) of the different regions in Japan.     

Activity of monomeric, dimeric, and trimeric flavonoids on NO production, TNF-alpha secretion, and NF-kappaB-dependent gene expression in RAW 264.7 macrophages

Flavonoids are potent antioxidants and have been associated with lowering the risk of cardiovascular diseases. In this study, the effect of flavonoids (monomers, dimers and a trimer) as well as French maritime pine bark extract, Pycnogenol, on NO production, tumor necrosis factor-alpha (TNF-alpha) secretion and nuclear factor (NF)-kappaB activity was compared. Monomers and dimers repressed NO production, TNF-alpha secretion and NF-kappaB-dependent gene expression induced by interferon gamma, whereas the trimeric procyanidin C2 and Pycnogenol enhanced these parameters. In addition, in unstimulated RAW 264.7 macrophages, both procyanidin C2 and Pycnogenol increased TNF-alpha secretion in a concentration- and time-dependent manner. These results demonstrate that procyanidins act as modulators of the immune response in macrophages.     

Differences between Bacterial Communities in the Gut of a Soil-Feeding Termite (Cubitermes niokoloensis) and Its Mounds

In tropical ecosystems, termite mound soils constitute an important soil compartment covering around 10% of African soils. Previous studies have shown (S. Fall, S. Nazaret, J. L. Chotte, and A. Brauman, Microb. Ecol. 28:191-199, 2004) that the bacterial genetic structure of the mounds of soil-feeding termites (Cubitermes niokoloensis) is different from that of their surrounding soil. The aim of this study was to characterize the specificity of bacterial communities within mounds with respect to the digestive and soil origins of the mound. We have compared the bacterial community structures of a termite mound, termite gut sections, and surrounding soil using PCR-denaturing gradient gel electrophoresis (DGGE) analysis and cloning and sequencing of PCR-amplified 16S rRNA gene fragments. DGGE analysis revealed a drastic difference between the genetic structures of the bacterial communities of the termite gut and the mound. Analysis of 266 clones, including 54 from excised bands, revealed a high level of diversity in each biota investigated. The soil-feeding termite mound was dominated by the Actinobacteria phylum, whereas the Firmicutes and Proteobacteria phyla dominate the gut sections of termites and the surrounding soil, respectively. Phylogenetic analyses revealed a distinct clustering of Actinobacteria phylotypes between the mound and the surrounding soil. The Actinobacteria clones of the termite mound were diverse, distributed among 10 distinct families, and like those in the termite gut environment lightly dominated by the Nocardioidaceae family. Our findings confirmed that the soil-feeding termite mound (C. niokoloensis) represents a specific bacterial habitat in the tropics.     

A comparative approach to the French medical missions in Brazil and in sub-Saharan Africa before the Second World War

Franco-Brazilian cooperation in the field of microbiology and tropical diseases dates back to the onset of those disciplines. Physicians were sent over by France, namely Marchoux, Simond and Salimbeni from 1901 to 1905 to study yellow fever, and Emile Brumpt from 1913 to 1914 to teach parasitology. These missions brought in some important results. After confirming that the yellow fever agent was a filterable virus and that Stegomya (Aedes) its only vector, Simond and Marchoux clarified the biology of the mosquito and showed that sexual transmission of the virus could occur. They also set up different measures for the control of yellow fever outbreaks which Oswaldo Cruz was inspired by for his campaign against yellow fever. Emile Brumpt implemented the teaching of parasitology at the Faculty of Medicine in S?o Paulo and contributed to human American trypanosomiasis by defining the transmission of the disease and the cycle of the parasite responsible for it. He also developed the technique known as xenodiagnosis. Simond and Marchoux's works on yellow fever found an immediate application in French colonies, particularly in sub-Saharan Africa. However, the fight against large African endemics such as sleeping sickness, the other human trypanosomiases, could not have been carried out successfully without the contribution of mobile teams following Eugène Jamot's initiative in addition to the permanent centres which characterized the French colonial system.     

Benchmarking the DFT methodology for assessing antioxidant-related properties: quercetin and edaravone as case studies

The overall objective was to identify an accurate computational electronic method to virtually screen phenolic compounds through their antioxidant and free-radical scavenging activity. The impact of a key parameter of the density functional theory (DFT) approach was studied. Performances of the 21 most commonly used exchange-correlation functionals are thus detailed in the evaluation of the main energetic parameters related to the activities of two prototype antioxidants, namely quercetin and edaravone, is reported. These functionals have been chosen among those belonging to three different families of hybrid functionals, namely global, range separated, and double hybrids. Other computational parameters have also been considered, such as basis set and solvent effects. The selected parameters, namely bond dissociation enthalpy (BDE), ionization potential (IP), and proton dissociation enthalpy (PDE) allow a mechanistic evaluation of the antioxidant activities of free radical scavengers. Our results show that all the selected functionals provide a coherent picture of these properties, predicting the same order of BDEs and PDEs. However, with respect to the reference values, the errors found at CBS-Q3 level significantly vary with the functional. Although it is difficult to evidence a global trend from the reported data, it clearly appears that LC-ωPBE, M05-2X, and M06-2X are the most suitable approaches for the considered properties, giving the lowest cumulative mean absolute errors. These methods are therefore suggested for an accurate and fast evaluation of energetic parameters related to an antioxidant activity via free radical scavenging.