The Experts below are selected from a list of 2340 Experts worldwide ranked by ideXlab platform

Jozef Vanden Broeck - One of the best experts on this subject based on the ideXlab platform.

  • The ecdysone receptor complex is essential for the reproductive success in the female Desert Locust, Schistocerca gregaria
    Scientific Reports, 2019
    Co-Authors: Cynthia Lenaerts, Elisabeth Marchal, Paulien Peeters, Jozef Vanden Broeck
    Abstract:

    Ecdysteroid hormones influence the development and reproduction of arthropods by binding a heterodimeric complex of nuclear receptors, the ecdysone receptor (EcR) and the retinoid-X-receptor/ultraspiracle (RXR/USP). Here, we report on the in vivo role(s) of the ecdysone receptor complex, SchgrEcR/SchgrRXR , in the female reproductive physiology of a major phytophagous pest insect, i.e. the Desert Locust, Schistocerca gregaria . Tissue and temporal distribution profiles were analysed during the first gonadotrophic cycle of adult female Locusts. RNA interference was used as a reverse genetics tool to investigate the in vivo role of the ecdysone receptor complex in ovarian maturation, oogenesis, fertility and fecundity. We discovered that silencing the ecdysone receptor complex in S. gregaria resulted in impaired ovulation and oviposition, indicative for a crucial role of this complex in chorion formation. We also found evidence for a feedback of SchgrEcR/SchgrRXR on juvenile hormone biosynthesis by the corpora allata. Furthermore, we observed a tissue-dependent effect of the SchgrEcR/SchgrRXR knockdown on the transcript levels of the insulin receptor and neuroparsin 3 and 4. The insulin receptor transcript levels were upregulated in the brain, but not the fat body and gonads. Neuroparsins 3 and 4 transcript levels were down regulated in the brain and fat body, but not in the gonads.

  • Role of the venus kinase receptor in the female reproductive physiology of the Desert Locust, Schistocerca gregaria
    Scientific Reports, 2017
    Co-Authors: Cynthia Lenaerts, Jolien Palmans, Elisabeth Marchal, Rik Verdonck, Jozef Vanden Broeck
    Abstract:

    Venus kinase receptors (VKR) are a subfamily of invertebrate receptor tyrosine kinases, which have only recently been discovered. They contain an intracellular tyrosine kinase domain and an extracellular Venus FlyTrap domain. VKRs have been functionally and pharmacologically characterized in only two invertebrate species, namely the human parasite Schistosoma mansoni and the mosquito Aedes aegypti , where they play a crucial role in oogenesis. Here, we report the characterization of a VKR in the Desert Locust, Schistocerca gregaria . We performed an in-depth profiling study of the SgVKR transcript levels in different tissues throughout the female adult stage. Using the RNA interference technique, the possible role of SgVKR was investigated. SgVKR knockdown had significant effects on ovarian ecdysteroid levels and on the size of oocytes during the vitellogenic stage. Sg VKR is probably involved in the complex cross-talk between several important pathways regulating female reproductive physiology. Contrary to A. aegypti and S. mansoni , we cannot conclude that this receptor is essential for reproduction, since silencing SgVKR did not affect fecundity or fertility. Considering the evolutionary distance between A. aegypti and S. gregaria , as well as the differences in regulation of their female reproductive physiology, this article constitutes a valuable asset in better understanding VKRs.

  • ecdysteroid signalling components in metamorphosis and development of the Desert Locust schistocerca gregaria
    Insect Biochemistry and Molecular Biology, 2016
    Co-Authors: Cynthia Lenaerts, Jozef Vanden Broeck, Paulien Peeters, Pieter Van Wielendaele, Elisabeth Marchal
    Abstract:

    The arthropod-specific hormone family of ecdysteroids plays an important role in regulating diverse physiological processes, such as moulting and metamorphosis, reproduction, diapause and innate immunity. Ecdysteroids mediate their response by binding to a heterodimeric complex of two nuclear receptors, the ecdysone receptor (EcR) and the retinoid-X-receptor/ultraspiracle (RXR/USP). In this study we investigated the role of EcR and RXR in metamorphosis and development of the Desert Locust, Schistocerca gregaria. The Desert Locust is a voracious, phytophagous, swarming pest that can ruin crops and harvests in some of the world's poorest countries. A profound knowledge of the ecdysteroid signalling pathway can be used in the development of more target-specific insecticides to combat this harmful plague insect. Here we report an in-depth profiling study of the transcript levels of EcR and RXR, as well as its downstream response genes, in different tissues isolated throughout the last larval stage of a hemimetabolous insect, showing a clear correlation with circulating ecdysteroid titres. Using RNA interference (RNAi), the role of SgEcR/SgRXR in moulting and development was investigated. We have proven the importance of the receptor components for successful moulting of Locust nymphs into the adult stage. Some SgEcR/SgRXR knockdown females were arrested in the last larval stage, and 65 % of them initiated vitellogenesis and oocyte maturation, which normally only occurs in adults. Furthermore, our results clearly indicate that at the peak of ecdysteroid synthesis, on day six of the last larval stage, knockdown of SgEcR/SgRXR is affecting the transcript levels of the Halloween genes, Spook, Shadow and Shade.

  • nutrient dependent control of short neuropeptide f transcript levels via components of the insulin igf signaling pathway in the Desert Locust schistocerca gregaria
    Insect Biochemistry and Molecular Biology, 2016
    Co-Authors: Senne Dillen, Ziwei Chen, Jozef Vanden Broeck
    Abstract:

    Peptides of the short neuropeptide F (sNPF) family modulate feeding behavior in a wide variety of insect species, including the Desert Locust, Schistocerca gregaria. Likewise, the nutritional state of the animal can strongly affect sNPF expression. Although several studies have been published describing these nutrient-dependent effects, it remains largely unclear how they are achieved. In this study, we describe a series of in vivo experiments which indicate that it is not the act of feeding in se, but rather the consequent availability of nutrients in the insect's hemolymph that gives rise to the postprandial modulation of sNPF expression. Furthermore, by performing a series of RNAi-mediated knockdown experiments, we were able to show that components of the evolutionarily conserved insulin/insulin-related growth factor (IGF) signaling pathway form a functional link between nutrient levels and sNPF transcript levels.

  • molecular cloning and characterization of the allatotropin precursor and receptor in the Desert Locust schistocerca gregaria
    Frontiers in Neuroscience, 2015
    Co-Authors: Els Lismont, Sven Zels, Liesbeth Badisco, Cynthia Lenaerts, Elisabeth Marchal, Stephen S Tobe, Pieter Van Wielendaele, Rut Vleugels, Jozef Vanden Broeck
    Abstract:

    Allatotropins (ATs) are pleiotropic neuropeptides initially isolated from the tobacco hornworm, Manduca sexta. In 2008, the first receptor for AT-like peptides (ATR) was characterized in Bombyx mori. Since then, ATRs have also been characterized in M. sexta, Tribolium castaneum, Aedes aegypti and Bombus terrestris. These receptors show sequence similarity to vertebrate orexin (ORX) receptors. When generating an EST-database of the Desert Locust (Schistocerca gregaria) central nervous system, we found cDNA sequences encoding the Schgr-AT precursor and a fragment of its putative receptor. This receptor cDNA has now been completed and functionally expressed in mammalian cell lines. Activation of this receptor, designated as Schgr-ATR, by Schgr-AT caused an increase in intracellular calcium ions, as well as cyclic AMP (cAMP), with an EC50 value in the nanomolar range. In addition, the transcript distribution of both the Schgr-AT precursor and Schgr-ATR was investigated by means of quantitative real-time PCR. Moreover, we found more evidence for the myotropic and allatostimulatory actions of Schgr-AT in the Desert Locust. These data are discussed and situated in a broader context by comparison with literature data on AT and ATR in insects.

Keith Cressman - One of the best experts on this subject based on the ideXlab platform.

  • prediction of breeding regions for the Desert Locust schistocerca gregaria in east africa
    Scientific Reports, 2020
    Co-Authors: Emily Kimathi, Keith Cressman, Henri E Z Tonnang, Sevgan Subramanian, Elfatih M Abdelrahman, Mehari Tesfayohannes, Saliou Niassy, Baldwyn Torto, Thomas Dubois, Chrysantus M Tanga
    Abstract:

    Desert Locust outbreak in East Africa is threatening livelihoods, food security, environment, and economic development in the region. The current magnitude of the Desert Locust invasion in East Africa is unprecedented and has not been witnessed for more than 70 years. Identifying the potential breeding sites of the pest is essential to carry out cost-effective and timely preventive measures before it inflicts significant damage. We accessed 9,134 Desert Locust occurrence records and applied a machine-learning algorithm to predict potential Desert Locust breeding sites in East Africa using key bio-climatic (temperature and rainfall) and edaphic (sand and moisture contents) factors. Ten days greenness maps from February 2020 to April 2020 were overlaid in model outputs to illustrate the temporal evolution of breeding site locations. This study demonstrated that vast areas of Kenya and Sudan, north eastern regions of Uganda, and south eastern and northern regions of South Sudan are at high risk of providing a conducive breeding environment for the Desert Locust. Our prediction results suggest that there is need to target these high-risk areas and strengthen ground surveillance to manage the pest in a timely, cost-effective, and environmentally friendly manner.

  • soil moisture from remote sensing to forecast Desert Locust presence
    Journal of Applied Ecology, 2019
    Co-Authors: Cyril Piou, Keith Cressman, Ahmed Salem Benahi, Mohamed Abdallahi Ould Babah Ebbe, Jamal Chihrane, Said Ghaout, Sory Cisse, Fakaba Diakite, Mohammed Lazar, Olivier Merlin
    Abstract:

    Preventive control of Desert Locusts is based on monitoring recession areas to detect outbreaks. Remote sensing has been increasingly used in the preventive control strategy. Soil moisture is a major ecological driver of Desert Locust populations but is still missing in the current imagery toolkit for preventive management. By means of statistical analyses, combining field observations of Locust presence/absence and soil moisture estimates at 1 km resolution from a disaggregation algorithm, we assess the potential of soil moisture to help preventive management of Desert Locust. We observe that a soil moisture dynamics increase of above 0.09 cm3/cm3 for 20 days followed by a decrease of soil moisture may increase the chance to observe Locusts 70 days later. We estimate the gains in early warning timing compared to using imagery from vegetation to be 3 weeks. We demonstrate that forecasting errors may be reduced by the combination of several types of indicators such as soil moisture and vegetation index in a common statistical model forecasting Locust presence. Policy implications. Soil moisture estimates at 1 km resolution should be used to plan Desert Locust surveys in preventive management. When soil moisture increases in a dry area of potential habitat for the Desert Locust, field surveys should be conducted two months later to evaluate the need of further preventive actions. Remote sensing estimates of soil moisture could also be used for other applications of integrated pest management.

  • Operational Monitoring of the Desert Locust Habitat with Earth Observation: An Assessment
    ISPRS International Journal of Geo-Information, 2015
    Co-Authors: Francois Waldner, Mohamed Ebbe, Keith Cressman, Pierre Defourny
    Abstract:

    Desert Locust swarms intermittently damage crops and pastures in sixty countries from Africa to western Asia, threatening the food security of 10% of the world’s population. During the 20th century, Desert Locust control operations began organizing, and nowadays, they are coordinated by the Food and Agriculture Organization (FAO), which promotes a preventative strategy based on early warning and rapid response. This strategy implies a constant monitoring of the populations and of the ecological conditions favorable to their development. Satellite remote sensing can provide a near real-time monitoring of these conditions at the continental scale. Thus, the Desert Locust control community needs a reliable detection of green vegetation in arid and semi-arid areas as an indicator of potential Desert Locust habitat. To meet this need, a colorimetric transformation has been developed on both SPOT-VEGETATION and MODIS data to produce dynamic greenness maps. After their integration in the daily Locust control activities, this research aimed at assessing those dynamic greenness maps from the producers’ and the users’ points of view. Eight confusion matrices and Pareto boundaries were derived from high resolution reference maps representative of the temporal and spatial diversity of Mauritanian habitats. The dynamic greenness maps were found to be accurate in summer breeding areas (F-score = 0.64–0.87), but accuracy dropped in winter breeding areas (F-score = 0.28–0.40). Accuracy is related to landscape fragmentation (R2 = 0.9): the current spatial resolution remains too coarse to resolve complex fragmented patterns and accounts for a substantial (60%) part of the error. The exploitation of PROBA-V 100-m images at the finest resolution (100-m) would enhance by 20% the vegetation detection in fragmented habitat. A survey revealed that end-users are satisfied with the product and find it fit for monitoring, thanks to an intuitive interpretation, leading to more efficiency.

  • role of remote sensing in Desert Locust early warning
    Journal of Applied Remote Sensing, 2013
    Co-Authors: Keith Cressman
    Abstract:

    Desert Locust (Schistocerca gregaria, Forskal) plagues have historically had devastating consequences on food security in Africa and Asia. The current strategy to reduce the frequency of plagues and manage Desert Locust infestations is early warning and preventive control. To achieve this, the Food and Agriculture Organization of the United Nations operates one of the oldest, largest, and best-known migratory pest monitoring systems in the world. Within this system, remote sensing plays an important role in detecting rainfall and green vegetation. Despite recent technological advances in data management and analysis, communications, and remote sensing, monitoring Desert Locusts and preventing plagues in the years ahead will continue to be a challenge from a geopolitical and financial standpoint for affected countries and the international donor community. We present an overview of the use of remote sensing in Desert Locust early warning.

  • Development and Application of Multi-Temporal Colorimetric Transformation to Monitor Vegetation in the Desert Locust Habitat
    IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2011
    Co-Authors: Jean François Pekel, Christelle Vancutsem, Eric Vanbogaert, Pietro Ceccato, Pierre Defourny, Keith Cressman
    Abstract:

    The Desert Locust (Schistocerca gregaria) is the most feared of all the Locusts worldwide. Satellite imagery can provide a continuous overview of ecological conditions (i.e., vegetation, soil moisture) suitable for the Desert Locust at the continental scale and in near real time. To monitor green vegetation, most remote sensing techniques are based on vegetation indices (e.g., NDVI). However, several limitations have been observed for this index based approaches in sparsely vegetated areas. To guarantee a more robust and reliable image-independent discrimination between vegetation and non-vegetated surface types, an innovative multi-temporal and multi-spectral image analysis method was developed based on a combination of MIR, NIR and Red reflectance measurements. The proposed approach is based on a transformation of the RGB color space into HSV that decouples chromaticity and luminance. A complete automatic processing chain combining the daily observations of MODIS and SPOT VEGETATION, was designed to provide user-friendly vegetation dynamic maps at 250 m resolution over the entire Locust area every 10 days. This new product informs users about the location of green vegetation and its temporal evolution. The methodology is currently implemented at the Vlaamse instelling voor technologisch onderzoek (VITO) to provide vegetation dynamic maps every dekade to the Desert Locust Information Service at FAO.

Cyril Piou - One of the best experts on this subject based on the ideXlab platform.

  • on the relative role of climate change and management in the current Desert Locust outbreak in east africa
    Global Change Biology, 2020
    Co-Authors: Christine N Meynard, Michel Lecoq, Marie Pierre Chapuis, Cyril Piou
    Abstract:

    While large-scale monitoring, early detection and control can greatly reduce Desert Locust invasions, global change is most likely to affect conditions that promote the transition from solitary to gregarious populations. Although climate change scenarios point to an increase in aridity and further Desertification in vast areas of Africa, some regions that have been at the origin of past outbreaks are likely to see a reversed trend (i.e., increase in frequency and intensity of rains), potentially favoring the formation of swarms. This makes reinforcing early detection and keeping a sustained monitoring effort in place even more important under climate change.

  • soil moisture from remote sensing to forecast Desert Locust presence
    Journal of Applied Ecology, 2019
    Co-Authors: Cyril Piou, Keith Cressman, Ahmed Salem Benahi, Mohamed Abdallahi Ould Babah Ebbe, Jamal Chihrane, Said Ghaout, Sory Cisse, Fakaba Diakite, Mohammed Lazar, Olivier Merlin
    Abstract:

    Preventive control of Desert Locusts is based on monitoring recession areas to detect outbreaks. Remote sensing has been increasingly used in the preventive control strategy. Soil moisture is a major ecological driver of Desert Locust populations but is still missing in the current imagery toolkit for preventive management. By means of statistical analyses, combining field observations of Locust presence/absence and soil moisture estimates at 1 km resolution from a disaggregation algorithm, we assess the potential of soil moisture to help preventive management of Desert Locust. We observe that a soil moisture dynamics increase of above 0.09 cm3/cm3 for 20 days followed by a decrease of soil moisture may increase the chance to observe Locusts 70 days later. We estimate the gains in early warning timing compared to using imagery from vegetation to be 3 weeks. We demonstrate that forecasting errors may be reduced by the combination of several types of indicators such as soil moisture and vegetation index in a common statistical model forecasting Locust presence. Policy implications. Soil moisture estimates at 1 km resolution should be used to plan Desert Locust surveys in preventive management. When soil moisture increases in a dry area of potential habitat for the Desert Locust, field surveys should be conducted two months later to evaluate the need of further preventive actions. Remote sensing estimates of soil moisture could also be used for other applications of integrated pest management.

  • mapping the spatiotemporal distributions of the Desert Locust in mauritania and morocco to improve preventive management
    Basic and Applied Ecology, 2017
    Co-Authors: Cyril Piou, Michel Lecoq, Mohamed Abdallahi Ould Babah Ebbe, Jamal Chihrane, Said Ghaout, Sory Cisse, Mohamed El Hacen Jaavar Bacar, Thami Ben Halima
    Abstract:

    Abstract Understanding Desert Locust population dynamics is a prerequisite for the implementation of a preventive management strategy against its invasions. The present study aims to describe these dynamics through conducting probability analyses of Locust presence in time and space. Historical data from field surveys conducted by management teams in Mauritania and Morocco for the period 1988–2015 were used. Temporal smoothing and spatio-temporal extrapolations were performed on a monthly basis. We established monthly probability maps of Locust observation following two scenarios: recession period (mainly solitarious phase) and invasion period (mainly gregarious phase). Also, observation probability maps of hoppers or mature adults allowed the identification of seasonal breeding areas. The methodology highlights the potentially favourable areas to be monitored every year. It also highlights the lack of information in some areas of the two countries. We observed that the seasonal survey process during recession periods follow the seasonal pattern of gregarious invasions. We argue that this is the result of climatic conditions related to the oscillation of the intertropical convergence zone. However, we advise that these similar yearly cycles should not hinder surveys in recession periods to be conducted in places not receiving swarms during invasion periods. Nevertheless, we conclude that these maps should be helpful for planning the preparation of survey teams in the field. This will reduce survey operation costs and decrease invasion risks.

  • challenges in estimating heritability of phase polyphenism insights from measured and simulated data in the Desert Locust
    bioRxiv, 2017
    Co-Authors: Helene Jourdanpineau, Benjamin Pelissie, Elodie Chapuis, Floriane Chardonnet, Christine Pages, Antoine Foucart, Laurence Blondin, Cyril Piou, Marie Pierre Chapuis
    Abstract:

    Quantitative genetics experiments aim at understanding and predicting the evolution of phenotypic traits. Running such experiments often bring the same questions: Should I bother with maternal effects? Could I estimate those effects? What is the best crossing scheme to obtain reliable estimates? Can I use molecular markers to spare time in the complex task of keeping track of the experimental pedigree? We explored those practical issues in the Desert Locust, Schistocerca gregaria using morphologic and coloration traits, known to be influenced by maternal effects. We ran quantitative genetic analyses with an experimental dataset and used simulations to explore i) the efficiency of animal models to accurately estimate both heritability and maternal effects, ii) the influence of crossing schemes on the precision of estimates and iii) the performance of a marker-based method compared to the pedigree-based method. The simulations indicated that maternal effects deeply affect heritability estimates and very large datasets are required to properly distinguish and estimate maternal effects and heritabilities. In particular, ignoring maternal effects in the animal model resulted in overestimation of heritabilities and a high rate of false positives whereas models specifying maternal variance suffer from lack of power. Maternal effects can be estimated more precisely than heritabilities but with low power. To obtain better estimates, bigger datasets are required and, in the presence of maternal effects, increasing the number of families over the number of offspring per families is recommended. Our simulations also showed that, in the Desert Locust, using relatedness based on available microsatellite markers may allow reasonably reliable estimates while rearing Locusts in group. In the light of the simulation results, our experimental dataset suggested that maternal effects affected various phase traits. However the statistical limitations, revealed by the simulation approach, didn9t allow precise variance estimates. We stressed out that doing simulations is a useful step to design an experiment in quantitative genetics and interpret the outputs of the statistical models.

  • effect of vegetation on density thresholds of adult Desert Locust gregarization from survey data in mauritania
    Entomologia Experimentalis Et Applicata, 2013
    Co-Authors: Sory Cisse, Ahmed Salem Benahi, Mohamed Abdallahi Ould Babah Ebbe, Said Ghaout, Ahmed Mazih, Cyril Piou
    Abstract:

    In the Desert Locust, Schistocerca gregaria (Forskal) (Orthoptera: Acrididae), the threshold density inducing the gregarization phenomenon has never been determined under natural conditions. The influence of environmental factors on this phenomenon has been studied mostly in controlled environments. Based on data collected during several years by the survey teams of the National Center for Locust Control in Mauritania, we analyzed the influence of Locust density, vegetation cover, and vegetation status on the probability of observing gregarious Locusts. We assumed that a probability to observe gregarious Locusts of 0.5 corresponded to the density threshold of gregarization. The results showed in detail the change in the threshold of gregarization according to the cover and status of the vegetation. Low cover and dry vegetation led to a low density threshold of gregarization probably due to high probability of individuals to touch each other. Dense and green vegetation favored a high threshold of gregarization probably due to a dispersion of the individuals and a low probability of individual encounters. These findings should help the management of Locusts and decision making during control operations. (Resume d'auteur)

Jamal Chihrane - One of the best experts on this subject based on the ideXlab platform.

  • soil moisture from remote sensing to forecast Desert Locust presence
    Journal of Applied Ecology, 2019
    Co-Authors: Cyril Piou, Keith Cressman, Ahmed Salem Benahi, Mohamed Abdallahi Ould Babah Ebbe, Jamal Chihrane, Said Ghaout, Sory Cisse, Fakaba Diakite, Mohammed Lazar, Olivier Merlin
    Abstract:

    Preventive control of Desert Locusts is based on monitoring recession areas to detect outbreaks. Remote sensing has been increasingly used in the preventive control strategy. Soil moisture is a major ecological driver of Desert Locust populations but is still missing in the current imagery toolkit for preventive management. By means of statistical analyses, combining field observations of Locust presence/absence and soil moisture estimates at 1 km resolution from a disaggregation algorithm, we assess the potential of soil moisture to help preventive management of Desert Locust. We observe that a soil moisture dynamics increase of above 0.09 cm3/cm3 for 20 days followed by a decrease of soil moisture may increase the chance to observe Locusts 70 days later. We estimate the gains in early warning timing compared to using imagery from vegetation to be 3 weeks. We demonstrate that forecasting errors may be reduced by the combination of several types of indicators such as soil moisture and vegetation index in a common statistical model forecasting Locust presence. Policy implications. Soil moisture estimates at 1 km resolution should be used to plan Desert Locust surveys in preventive management. When soil moisture increases in a dry area of potential habitat for the Desert Locust, field surveys should be conducted two months later to evaluate the need of further preventive actions. Remote sensing estimates of soil moisture could also be used for other applications of integrated pest management.

  • smos based high resolution soil moisture estimates for Desert Locust preventive management
    Remote Sensing Applications: Society and Environment, 2018
    Co-Authors: Mariajose Escorihuela, Ahmed Salem Benahi, Mohamed Abdallahi Ould Babah Ebbe, Olivier Merlin, Vivien Stefan, Gorka Moyano, Omar Ali Eweys, Mehrez Zribi, Sidi Kamara, Jamal Chihrane
    Abstract:

    Abstract This paper presents the first attempt to include soil moisture information from remote sensing in the tools available to Desert Locust managers. The soil moisture requirements were first assessed with the users. The main objectives of this paper are: i) to describe and validate the algorithms used to produce a soil moisture dataset at 1 km resolution relevant to Desert Locust management based on DisPATCh methodology applied to SMOS and ii) the development of an innovative approach to derive high-resolution (100 m) soil moisture products from Sentinel-1 in synergy with SMOS data. For the purpose of soil moisture validation, 4 soil moisture stations where installed in Desert areas (one in each user country). The soil moisture 1 km product was thoroughly validated and its accuracy is amongst the best available soil moisture products. Current comparison with in-situ soil moisture stations shows good values of correlation ( R > 0.7 ) and low RMSE (below 0.04 m3 m−3). The low number of acquisitions on wet dates has limited the development of the soil moisture 100 m product over the Users Areas. The Soil Moisture product at 1 km will be integrated into the national and global Desert Locust early warning systems in national Locust centres and at DLIS-FAO, respectively.

  • mapping the spatiotemporal distributions of the Desert Locust in mauritania and morocco to improve preventive management
    Basic and Applied Ecology, 2017
    Co-Authors: Cyril Piou, Michel Lecoq, Mohamed Abdallahi Ould Babah Ebbe, Jamal Chihrane, Said Ghaout, Sory Cisse, Mohamed El Hacen Jaavar Bacar, Thami Ben Halima
    Abstract:

    Abstract Understanding Desert Locust population dynamics is a prerequisite for the implementation of a preventive management strategy against its invasions. The present study aims to describe these dynamics through conducting probability analyses of Locust presence in time and space. Historical data from field surveys conducted by management teams in Mauritania and Morocco for the period 1988–2015 were used. Temporal smoothing and spatio-temporal extrapolations were performed on a monthly basis. We established monthly probability maps of Locust observation following two scenarios: recession period (mainly solitarious phase) and invasion period (mainly gregarious phase). Also, observation probability maps of hoppers or mature adults allowed the identification of seasonal breeding areas. The methodology highlights the potentially favourable areas to be monitored every year. It also highlights the lack of information in some areas of the two countries. We observed that the seasonal survey process during recession periods follow the seasonal pattern of gregarious invasions. We argue that this is the result of climatic conditions related to the oscillation of the intertropical convergence zone. However, we advise that these similar yearly cycles should not hinder surveys in recession periods to be conducted in places not receiving swarms during invasion periods. Nevertheless, we conclude that these maps should be helpful for planning the preparation of survey teams in the field. This will reduce survey operation costs and decrease invasion risks.

Elisabeth Marchal - One of the best experts on this subject based on the ideXlab platform.

  • The ecdysone receptor complex is essential for the reproductive success in the female Desert Locust, Schistocerca gregaria
    Scientific Reports, 2019
    Co-Authors: Cynthia Lenaerts, Elisabeth Marchal, Paulien Peeters, Jozef Vanden Broeck
    Abstract:

    Ecdysteroid hormones influence the development and reproduction of arthropods by binding a heterodimeric complex of nuclear receptors, the ecdysone receptor (EcR) and the retinoid-X-receptor/ultraspiracle (RXR/USP). Here, we report on the in vivo role(s) of the ecdysone receptor complex, SchgrEcR/SchgrRXR , in the female reproductive physiology of a major phytophagous pest insect, i.e. the Desert Locust, Schistocerca gregaria . Tissue and temporal distribution profiles were analysed during the first gonadotrophic cycle of adult female Locusts. RNA interference was used as a reverse genetics tool to investigate the in vivo role of the ecdysone receptor complex in ovarian maturation, oogenesis, fertility and fecundity. We discovered that silencing the ecdysone receptor complex in S. gregaria resulted in impaired ovulation and oviposition, indicative for a crucial role of this complex in chorion formation. We also found evidence for a feedback of SchgrEcR/SchgrRXR on juvenile hormone biosynthesis by the corpora allata. Furthermore, we observed a tissue-dependent effect of the SchgrEcR/SchgrRXR knockdown on the transcript levels of the insulin receptor and neuroparsin 3 and 4. The insulin receptor transcript levels were upregulated in the brain, but not the fat body and gonads. Neuroparsins 3 and 4 transcript levels were down regulated in the brain and fat body, but not in the gonads.

  • Role of the venus kinase receptor in the female reproductive physiology of the Desert Locust, Schistocerca gregaria
    Scientific Reports, 2017
    Co-Authors: Cynthia Lenaerts, Jolien Palmans, Elisabeth Marchal, Rik Verdonck, Jozef Vanden Broeck
    Abstract:

    Venus kinase receptors (VKR) are a subfamily of invertebrate receptor tyrosine kinases, which have only recently been discovered. They contain an intracellular tyrosine kinase domain and an extracellular Venus FlyTrap domain. VKRs have been functionally and pharmacologically characterized in only two invertebrate species, namely the human parasite Schistosoma mansoni and the mosquito Aedes aegypti , where they play a crucial role in oogenesis. Here, we report the characterization of a VKR in the Desert Locust, Schistocerca gregaria . We performed an in-depth profiling study of the SgVKR transcript levels in different tissues throughout the female adult stage. Using the RNA interference technique, the possible role of SgVKR was investigated. SgVKR knockdown had significant effects on ovarian ecdysteroid levels and on the size of oocytes during the vitellogenic stage. Sg VKR is probably involved in the complex cross-talk between several important pathways regulating female reproductive physiology. Contrary to A. aegypti and S. mansoni , we cannot conclude that this receptor is essential for reproduction, since silencing SgVKR did not affect fecundity or fertility. Considering the evolutionary distance between A. aegypti and S. gregaria , as well as the differences in regulation of their female reproductive physiology, this article constitutes a valuable asset in better understanding VKRs.

  • ecdysteroid signalling components in metamorphosis and development of the Desert Locust schistocerca gregaria
    Insect Biochemistry and Molecular Biology, 2016
    Co-Authors: Cynthia Lenaerts, Jozef Vanden Broeck, Paulien Peeters, Pieter Van Wielendaele, Elisabeth Marchal
    Abstract:

    The arthropod-specific hormone family of ecdysteroids plays an important role in regulating diverse physiological processes, such as moulting and metamorphosis, reproduction, diapause and innate immunity. Ecdysteroids mediate their response by binding to a heterodimeric complex of two nuclear receptors, the ecdysone receptor (EcR) and the retinoid-X-receptor/ultraspiracle (RXR/USP). In this study we investigated the role of EcR and RXR in metamorphosis and development of the Desert Locust, Schistocerca gregaria. The Desert Locust is a voracious, phytophagous, swarming pest that can ruin crops and harvests in some of the world's poorest countries. A profound knowledge of the ecdysteroid signalling pathway can be used in the development of more target-specific insecticides to combat this harmful plague insect. Here we report an in-depth profiling study of the transcript levels of EcR and RXR, as well as its downstream response genes, in different tissues isolated throughout the last larval stage of a hemimetabolous insect, showing a clear correlation with circulating ecdysteroid titres. Using RNA interference (RNAi), the role of SgEcR/SgRXR in moulting and development was investigated. We have proven the importance of the receptor components for successful moulting of Locust nymphs into the adult stage. Some SgEcR/SgRXR knockdown females were arrested in the last larval stage, and 65 % of them initiated vitellogenesis and oocyte maturation, which normally only occurs in adults. Furthermore, our results clearly indicate that at the peak of ecdysteroid synthesis, on day six of the last larval stage, knockdown of SgEcR/SgRXR is affecting the transcript levels of the Halloween genes, Spook, Shadow and Shade.

  • molecular cloning and characterization of the allatotropin precursor and receptor in the Desert Locust schistocerca gregaria
    Frontiers in Neuroscience, 2015
    Co-Authors: Els Lismont, Sven Zels, Liesbeth Badisco, Cynthia Lenaerts, Elisabeth Marchal, Stephen S Tobe, Pieter Van Wielendaele, Rut Vleugels, Jozef Vanden Broeck
    Abstract:

    Allatotropins (ATs) are pleiotropic neuropeptides initially isolated from the tobacco hornworm, Manduca sexta. In 2008, the first receptor for AT-like peptides (ATR) was characterized in Bombyx mori. Since then, ATRs have also been characterized in M. sexta, Tribolium castaneum, Aedes aegypti and Bombus terrestris. These receptors show sequence similarity to vertebrate orexin (ORX) receptors. When generating an EST-database of the Desert Locust (Schistocerca gregaria) central nervous system, we found cDNA sequences encoding the Schgr-AT precursor and a fragment of its putative receptor. This receptor cDNA has now been completed and functionally expressed in mammalian cell lines. Activation of this receptor, designated as Schgr-ATR, by Schgr-AT caused an increase in intracellular calcium ions, as well as cyclic AMP (cAMP), with an EC50 value in the nanomolar range. In addition, the transcript distribution of both the Schgr-AT precursor and Schgr-ATR was investigated by means of quantitative real-time PCR. Moreover, we found more evidence for the myotropic and allatostimulatory actions of Schgr-AT in the Desert Locust. These data are discussed and situated in a broader context by comparison with literature data on AT and ATR in insects.

  • CRF-Like Diuretic Hormone Negatively Affects Both Feeding and Reproduction in the Desert Locust,
    2013
    Co-Authors: Schistocerca Gregaria, Senne Dillen, Liesbeth Badisco, Elisabeth Marchal, Pieter Van Wielendaele, En Broeck
    Abstract:

    Diuretic hormones (DH) related to the vertebrate Corticotropin Releasing Factor (CRF) have been identified in diverse insect species. In the migratory Locust, Locusta migratoria, the CRF-like DH (CRF/DH) is localized in the same neurosecretory cells as the Ovary Maturating Parsin (OMP), a neurohormone that stimulates oocyte growth, vitellogenesis and hemolymph ecdysteroid levels in adult female Locusts. In this study, we investigated whether CRF-like DH can influence feeding and reproduction in the Desert Locust, Schistocerca gregaria. We identified two highly similar S. gregaria CRF-like DH precursor cDNAs, each of which also encodes an OMP isoform. Alignment with other insect CRF-like DH precursors shows relatively high conservation of the CRF/DH sequence while the precursor region corresponding to OMP is not well conserved. Quantitative real-time RT-PCR revealed that the precursor transcripts mainly occur in the central nervous system and their highest expression level was observed in the brain. Injection of Locust CRF/DH caused a significantly reduced food intake, while RNAi knockdown stimulated food intake. Therefore, our data indicate that CRF-like DH induces satiety. Furthermore, injection of CRF/DH in adult females retarded oocyte growth and caused lower ecdysteroid titers in hemolymph and ovaries, while RNAi knockdown resulted in opposite effects. The observed effects of CRF/DH may be part of a wider repertoire of neurohormonal activities, constituting an integrating control system that affects food intake and excretion, as well as anabolic processes like oocyte growth and ecdysteroidogenesis, following a meal. Our discussion about th