Dependence on multiple nutritional bacterial symbionts forming a metabolic unit has repeatedly ev... more Dependence on multiple nutritional bacterial symbionts forming a metabolic unit has repeatedly evolved in many insect species that feed on nutritionally unbalanced diets such as plant sap. This is the case for aphids of the subfamilies Lachninae and Chaitophorinae, which have evolved di-symbiotic systems in which the ancient obligate nutritional symbiont Buchnera aphidicola is metabolically complemented by an additional nutritional symbiont acquired more recently. Deciphering how different symbionts integrate both metabolically and anatomically in such systems is crucial to understanding how complex nutritional symbiotic systems function and evolve. In this study, we sequenced and analyzed the genomes of the symbionts B. aphidicola and Serratia symbiotica associated with the Chaitophorinae aphids Sipha maydis and Periphyllus lyropictus. Our results show that, in these two species, B. aphidicola and S. symbiotica complement each other metabolically (and their hosts) for the biosynthe...
Multipartner nutritional endosymbioses have evolved many times in insects. In Chaitophorinae aphi... more Multipartner nutritional endosymbioses have evolved many times in insects. In Chaitophorinae aphids, the eroded metabolic capabilities of the ancient obligate symbiont B. aphidicola are complemented by those of more recently acquired symbionts.
African Journal of Agricultural Research, Apr 30, 2007
The bruchid Callosobruchus maculatus (F.) (Coleopetera: Bruchidae) is a major pest of stored cowp... more The bruchid Callosobruchus maculatus (F.) (Coleopetera: Bruchidae) is a major pest of stored cowpea Vigna unguiculata (Walp.) in Africa and particularly in northern Cameroon. Anisopteromalus calandrae (Hymenoptera: Pteromalidae) parasitoid of its larval stages, could be used in the biological control of this grain pest. In field conditions, 5 months samples in small holder granaries established the phenological relationship between this parasitoid and its host. Large amount of A. calandrae may efficiently control C. maculatus infestations. Laboratory assays made an evidence of the preference of A. calandrae to parasitise 4th instar larvae of C. maculatus. To estimate the suitable density of the infesting population of parasitoid, other experiments pointed out that one mated female induced reduction of 4.97% of emergence of C. maculatus while 4 females performed more. The reduction of emergence observed was 42.34%. In suitable density, A. calandrae may play an important role in the biological control of C. maculatus on cowpea during storage.
Although synthetic pesticides are still used to control insect pests, greater efforts have been m... more Although synthetic pesticides are still used to control insect pests, greater efforts have been made to develop healthier and more environmentally friendly pesticides. Because of their insecticidal properties, botanical essential oils (EOs) are considered as promising alternatives to the use of synthetic insecticides. However, little is known about mechanisms underlying the insecticidal activity of most these natural compounds. In the present study, we evaluated the contact toxicity and the modes of action of the EO from Mentha arvensis against the granary weevil, Sitophilus granarius L. (Coleoptera: Curculionidae), a cosmopolitan insect pest that causes extensive damage to stored cereals. M. arvensis EO caused high contact toxicity in S. granarius adults, resulting in a rapid paralysis and rapid alteration of walking behavior. Our label-free quantitative proteomics approach revealed that M. arvensis EO induced dramatic physiological changes in exposed insects. The majority of the differentially expressed proteins (DEPs) were upregulated and are related to the development and functioning of the muscular and nervous systems, cellular respiration, protein synthesis, and detoxification. These results suggest that M. arvensis essential oil is capable of affecting a variety of biological processes, and shed light on the repair mechanisms put in place in surviving insects to counter the damage inflicted. This work opens new perspectives on the proposed mechanisms of insecticidal activity of a promising EO for controlling pests of stored cereals and may represent a first step in the development of novel bio-rational insecticides. Biopesticide • Insecticidal activity • Label-free quantitative proteomics • Mentha • Sodalis • Weevil Key message • Studies on the use of essential oils (EOs) as insecticides are abundant, but little is known about their modes of action. • Mentha arvensis EO caused high contact toxicity in Sitophilus granarius adults resulting in rapid alteration of walking behavior. • By penetrating the insect cuticle, M. arvensis EO induced dramatic physiological changes. • This work shed light on the modes of action of a promising candidate in the development of EO-based insecticides against pests of stored cereals. Communicated by Murray Isman.
The granary weevil Sitophilus granarius is a stored product pest found worldwide. Environmental d... more The granary weevil Sitophilus granarius is a stored product pest found worldwide. Environmental damages, human health issues and the emergence of resistance are driving scientists to seeks alternatives to synthetic insecticides for its control. With low mammal toxicity and low persistence, essential oils are more and more being considered a potential alternative. In this study, we compare the toxicity of 25 essential oils, representing a large array of chemical compositions, on adult granary weevils. Bioassays indicated that Allium sativum was the most toxic essential oil, with the lowest calculated lethal concentration 90 (LC90) both after 24 h and 7 days. Gaultheria procumbens, Mentha arvensis and Eucalyptus dives oils appeared to have a good potential in terms of toxicity/cost ratio for further development of a plant-derived biocide. Low influence of exposure time was observed for most of essential oils. The methodology developed here offers the possibility to test a large array ...
The European crabapple Malus sylvestris, a crop wild relative of Malus domestica, is a major cont... more The European crabapple Malus sylvestris, a crop wild relative of Malus domestica, is a major contributor to the cultivated apple genome and represents a potential source of interesting alleles or genes, particularly pest resistance traits. An original approach was used to explore the trophic interaction between M. sylvestris populations and its pest, the rosy apple aphid (Dysaphis plantaginea). Using 13 microsatellite markers, population genetic structure and level of crop-to-wild introgressions were inferred between M. sylvestris seedlings from three sites in Europe (Denmark, France, Romania), and M. domestica seedlings. Genetically characterized plants were also used to analyze aphid feeding behavior and fitness parameters. First, aphids submitted to two genetically close M. sylvestris populations (the Danish and French) exhibited similar behavioral parameters, suggesting similar patterns of resistance in these host plants. Second, the Romanian M. sylvestris population was most cl...
Fruit flies are one of the world’s most devastating crop pests, causing millions of Dollars in pr... more Fruit flies are one of the world’s most devastating crop pests, causing millions of Dollars in production loss each year. In Africa there are several species that attack fruits, vegetables and native hosts. Among these are two species that have recently invaded Africa: Bactrocera invadens and B. cucurbitae (Diptera: Tephritidae family). These two species attack a wide variety of crops including mango, guava and tomato. B. invadens, an invasive fruit fly from Asia, also infests citrus and cashew nuts. Since its first detection in Kenya in 2003, B. invadens has spread to 26 countries in Africa and is known to infest at least 31 host plants. Both B. invadens and B. cucurbitae are devastating pests that can have a severe impact on sustainable agriculture and rural livelihoods, as well as export markets. No serious fruit fly surveys had ever been undertaken in Rwanda and it was not known whether B. invadens occurred in that country, nor were there any inventories of Tephritidae available...
We sampled the mites present on individuals of Rhynchophorus phoenicis collected at different sit... more We sampled the mites present on individuals of Rhynchophorus phoenicis collected at different sites in the Kisangani region of the Democratic Republic of the Congo. Two species belonging to two families (Uroactiniidae and Urodinychidae) were identified: Centrouropoda almerodai and Uroobovella phoenicola. This is the first time that C. almerodai has been reported on R. phoenicis. The number of mites per adult may reach 39 and differs between sexes and regions.
BackgroundPulsed ultraviolet (UV)-C light sources, such as excimer lasers, are used in emerging n... more BackgroundPulsed ultraviolet (UV)-C light sources, such as excimer lasers, are used in emerging non-thermal food-decontamination methods and also have high potential for use in a wide range of microbial decontamination applications. The acaricidal effect of an experimental UV-C irradiation device was assessed using female adults and eggs of a model organism, the two-spotted spider miteTetranychus urticae.MethodsUV-C light was generated by a pulsed krypton fluoride excimer laser operating at 248-nm emission wavelength. The pulse energy and pulse repetition rate were 5 mJ and up to 100 Hz, respectively. The distance from the light source to the target was 150 mm; the target surface area was 2.16 cm2. The exposure time for the mites and fresh eggs varied from 1 to 4 min at 5–300 mW, which corresponded to UV doses of 5–80 kJ/m2. Post-irradiation acaricidal effects (mite mortality) were assessed immediately and also measured at 24 h. The effects of UV-C irradiation on the hatchability of...
African Journal of Food, Agriculture, Nutrition and Development, 2007
Animal feed is food constituted for breeding stock animals because it possesses vital nutrients f... more Animal feed is food constituted for breeding stock animals because it possesses vital nutrients for animal growth. Animal feed or their ingredients as constituted by cereal flour and are stored after formulation for ulterior breeds. These provender or cereal grains used are commonly attacked by storage insects principally of the genus Tribolium . Firstly, contact and ingestion test by two essential oils of aromatics plants Ocimum gratissimum L (Lamiaceae) and Xylopia aethiopica Dunal A. Rich (Annonaceae) were done firstly on adults and aged larvae of Tribolium castaneun . Secondly, the contact and inhalation test by three essential oils of the aromatic plants Annona senegalensis L. (Annonaceae), Lippia rugosa L. (Lamiaceae) and Hyptis spicigera Lam. (Verbenaceae) were done for the control larvae, young and aged adults of the red flour weevil Tribolium castaneum Herbst (Coleoptera : Tenebrionidae) very resistant pest to chemical pesticides. Essential oils of Ocimum gratissimum and Xy...
Frontiers in Cellular and Infection Microbiology, 2021
Mutualistic associations between insects and heritable bacterial symbionts are ubiquitous in natu... more Mutualistic associations between insects and heritable bacterial symbionts are ubiquitous in nature. The aphid symbiont Serratia symbiotica is a valuable candidate for studying the evolution of bacterial symbiosis in insects because it includes a wide diversity of strains that reflect the diverse relationships in which bacteria can be engaged with insects, from pathogenic interactions to obligate intracellular mutualism. The recent discovery of culturable strains, which are hypothesized to resemble the ancestors of intracellular strains, provide an opportunity to study the mechanisms underlying bacterial symbiosis in its early stages. In this study, we analyzed the genomes of three of these culturable strains that are pathogenic to aphid hosts, and performed comparative genomic analyses including mutualistic host-dependent strains. All three genomes are larger than those of the host-restricted S. symbiotica strains described so far, and show significant enrichment in pseudogenes and...
ABSTRACTBacterial symbioses are significant drivers of insect evolutionary ecology. However, desp... more ABSTRACTBacterial symbioses are significant drivers of insect evolutionary ecology. However, despite recent findings that these associations can emerge from environmentally derived bacterial precursors, there is still little information on how these potential progenitors of insect symbionts circulates in the trophic systems. The aphid symbiont Serratia symbiotica represents a valuable model for deciphering evolutionary scenarios of bacterial acquisition by insects, as its diversity includes intracellular host-dependent strains as well as gut-associated strains that have retained some ability to live independently of their hosts and circulate in plant phloem sap. These strains represent a potential reservoir for the emergence of new and more intimate symbioses. Here, we conducted a field study to examine the distribution and diversity of S. symbiotica found in aphid populations, as well as in different compartments of their surrounding environment. A total of 250 aphid colonies, 203 ...
Background While pulsed UV-C light sources such as excimer lasers are used in emerging non-therma... more Background While pulsed UV-C light sources such as excimer lasers are used in emerging non-thermal food decontamination method, they also have a high potential for a wide range of other microbial decontamination applications. The acaricidal effect of an experimental UV-C irradiation device was assessed using two-spotted spider mite female adults Tetranychus urticae and eggs as a model. Methods The UV-C light source was generated by a pulsed krypton fluoride (KrF) excimer laser operating at 248 nm emission wavelength. Pulse energy and pulse repetition rate were 5mJ, and up to 100Hz rate, respectively. Distance from light source to target was 150 mm with a target surface of 21.6 cm². The exposure time of the mite and fresh eggs varied from 1 to 4 minutes at a power of 300 mW. The post-irradiation acaricidal effects (mites’ mortality) were assessed immediately and measured 24 h post-irradiation. Effects on the hatchability of irradiated eggs were observed daily post-irradiation for up ...
The use of conventional pesticides is debated because of their multiple potential adverse effects... more The use of conventional pesticides is debated because of their multiple potential adverse effects on non-target organisms, human health, pest resistance development and environmental contaminations. In this setting, this study focused on developing alternatives, such as trunk-injected essential oil (EO)-based biopesticides. We analysed the ecophysiology of apple trees (Malus domestica) following the injection ofCinnamomum cassiaandMentha spicatananoemulsions in the tree’s vascular system. Targeted and untargeted volatile organic compounds (VOCs) analyses were performed on leaf-contained and leaf-emitted VOCs and analysed through dynamic headspace–gas chromatography–mass spectrometry (DHS-GC-MS) and thermal desorption unit (TDU)-GC-MS. Our results showed that carvone, as a major constituent of theM. spicataEO, was contained in the leaves (mean concentrations ranging from 3.39 to 19.7 ng gDW–1) and emitted at a constant rate of approximately 0.2 ng gDW–1h–1.Trans-cinnamaldehyde,C. cas...
Over the last few decades, numerous examples have been described where a trait that was once lost... more Over the last few decades, numerous examples have been described where a trait that was once lost during the course of evolution had been regained. Here, we argue that such reverse evolution can also become apparent when trait expression is plastic in response to the environment. We tested this hypothesis for the loss and regain of fat synthesis in parasitic wasps. Wasps from lineages that supposedly regained lipogenic ability ~80 million years ago were grown under a fat-poor or fat-rich environment. In line with our hypothesis, it turned out that fat synthesis had not been lost and regained, but was only switched on in low-fat environments. Functional protein domains of key lipogenesis genes were also found in other parasitoid species, suggesting that plasticity of fat synthesis may be more widespread in parasitoids. Individual-based simulations then revealed that a switch for plastic expression can remain functional in the genome for thousands of generations, even if it is only us...
Intercropping is an agricultural practice consisting in planting two or several crops in the same... more Intercropping is an agricultural practice consisting in planting two or several crops in the same field simultaneously. This production system appeared to offer an excellent several advantages. While intercropping has been widely practiced since ancestral times, there was a lack of data in Rwanda on the kind of intercrops mostly used and on farmers’ perception of their utility and constraints. The main objectives of this work were (1) to assess the different food crops associated with coffee trees in Rwanda and (2) to determine the perception of farmers on the role of intercropping system. That was why a field survey was carried out between August 25th, 2014 and February 28th, 2015 in Kamonyi District of Rwanda. Seventy-five coffee producers were randomly selected and contacted to fill a questionnaire on their practices. The correlation between yield and pesticide application were performed using R version. The significance level P was set at 0.05. Results revealed that common beans...
Serratia symbiotica , one of the most frequent symbiont species in aphids, includes strains that ... more Serratia symbiotica , one of the most frequent symbiont species in aphids, includes strains that exhibit various lifestyles ranging from free-living to obligate intracellular mutualism. Here, we report the draft genome sequences of two strains, namely, 24.1 and Apa8A1, isolated from aphids of the genus Aphis , consisting of genome sizes of 3,089,091 bp and 3,232,107 bp, respectively. These genome sequences may provide new insights into how mutualistic interactions between bacteria and insects evolve and are shaped.
African Journal of Food Science and Technology, 2017
Entomophagy (consumption of insects) is more and more regarded as a possibility to solve food pro... more Entomophagy (consumption of insects) is more and more regarded as a possibility to solve food problems of deficiencies or malnutrition. Our objective was to analyze the possibility of rearing the Rhynchophorus phoenicis weevil on side products resulting from agriculture in order to improve its availability at an acceptable cost by the local populations. All experiments were done under basic local conditions and using local products. To this end, we carried out the breeding of R. phoenicis on five types of substrates (old and young palm trunk split in two parts and reassembled or not, sugar canes and two artificial diets) by using either eggs, or first stage larvae to start the production. The young palm trunk gave a much better production when not split, with shorter development duration (15 days against at least 35 days) and heavier last stage larvae (6, 95 g vs 3.4g) on this substrate than on all the others. However, pieces of sugar cane and artificial diet based on plantain-sweet potato pasta added with cowpea gave encouraging results. Larval infestation worked better than eggs infestation. This work underlined the potential of R. phoenicis rearing under the conditions of poor developing countries.
Symbiosis is a common phenomenon in nature that substantially affects organismal ecology and evol... more Symbiosis is a common phenomenon in nature that substantially affects organismal ecology and evolution. Fundamental questions regarding how mutualistic associations arise and evolve in nature remain, however, poorly studied. The aphid-Serratia symbiotica bacterium interaction represents a valuable model to study mechanisms shaping these symbiotic interspecific interactions. S. symbiotica strains capable of living independently of aphid hosts have recently been isolated. These strains probably resulted from horizontal transfers and could be an evolutionary link to an intra-organismal symbiosis. In this context, we used the tripartite interaction between the aphid Aphis fabae, a cultivable S. symbiotica bacterium, and the host plant Vicia faba to evaluate the bacterium ability to circulate in this system, exploring its environmental acquisition by aphids and horizontal transmission between aphids via the host plant. Using molecular analyses and fluorescence techniques, we showed that the cultivable S. symbiotica can enter the plants and induce new bacterial infections in aphids feeding on these new infected plants. Remarkably, we also found that the bacterium can have positive effects on the host plant, mainly at the root level. Furthermore, our results demonstrated that cultivable S. symbiotica can be horizontally transferred from infected to uninfected aphids sharing the same plant, providing first direct evidence that plants can mediate horizontal transmission of certain strains of this symbiont species. These findings highlight the importance of considering symbiotic associations in complex systems where microorganisms can circulate between different compartments. Our study can thus have major implications for understanding the multifaceted interactions between microbes, insects and plants.
Symbiotic bacteria are common in insects and can affect various aspects of their hosts' biolo... more Symbiotic bacteria are common in insects and can affect various aspects of their hosts' biology. Although the effects of insect symbionts have been clarified for various insect symbiosis models, due to the difficulty of cultivating them in vitro, there is still limited knowledge available on the molecular features that drive symbiosis. Serratia symbiotica is one of the most common symbionts found in aphids. The recent findings of free-living strains that are considered as nascent partners of aphids provide the opportunity to examine the molecular mechanisms that a symbiont can deploy at the early stages of the symbiosis (i.e., symbiotic factors). In this work, a proteomic approach was used to establish a comprehensive proteome map of the free-living S. symbiotica strain CWBI-2.3(T). Most of the 720 proteins identified are related to housekeeping or primary metabolism. Of these, 76 were identified as candidate proteins possibly promoting host colonization. Our results provide str...
Uploads
Papers by Thierry Hance