Plant Pests of the Middle East


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The Department of Entomology
The Robert H. Smith Faculty of Agriculture, Food and Environment
The Hebrew University of Jerusalem
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Akami, M. ; Andongma, A. A. ; Zhengzhong, C. ; Nan, J. ; Khaeso, K. ; Jurkevitch, E. ; Niu, C. - Y. ; Yuval, B. Intestinal bacteria modulate the foraging behavior of the oriental fruit fly Bactrocera dorsalis (Diptera: Tephritidae). PLoS One 2019, 14, e0210109.Abstract
The gut microbiome of insects directly or indirectly affects the metabolism, immune status, sensory perception and feeding behavior of its host. Here, we examine the hypothesis that in the oriental fruit fly (Bactrocera dorsalis, Diptera: Tephritidae), the presence or absence of gut symbionts affects foraging behavior and nutrient ingestion. We offered protein-starved flies, symbiotic or aposymbiotic, a choice between diets containing all amino acids or only the non-essential ones. The different diets were presented in a foraging arena as drops that varied in their size and density, creating an imbalanced foraging environment. Suppressing the microbiome resulted in significant changes of the foraging behavior of both male and female flies. Aposymbiotic flies responded faster to the diets offered in experimental arenas, spent more time feeding, ingested more drops of food, and were constrained to feed on time-consuming patches (containing small drops of food), when these offered the full complement of amino acids. We discuss these results in the context of previous studies on the effect of the gut microbiome on host behavior, and suggest that these be extended to the life history dimension.
Jose, P. A. ; Ben-Yosef, M. ; Jurkevitch, E. ; Yuval, B. Symbiotic bacteria affect oviposition behavior in the olive fruit fly Bactrocera oleae. J Insect Physiol 2019, 117, 103917.Abstract
Microbial associations are widespread across the insects. In the olive fruit fly Bactrocera oleae (Diptera: Tephritidae), vertically transmitted gut symbionts contribute to larval development inside the olive host, and to adult nutrition. Nevertheless, their effect on behavioural decisions of adults is unknown. In this study, we show that symbiotic bacteria affect oviposition behaviour in B. oleae. We studied the effect of different fruits as hosts and different gut-bacteria as gut-symbionts on oviposition attempts and fly development in B. oleae. Untreated flies that had native gut-symbionts attempted oviposition significantly more times than axenic flies as well as flies treated with medfly-associated Pantoea or Klebsiella bacteria. Axenic flies provided with a diet containing the homogenized gut of symbiotic flies recovered the same number of oviposition attempts as their symbiotic counterparts. As for as the different hosts, green olives (unripe) and grapes were preferred while black olives (ripe) elicited the least number of oviposition attempts, with an interactive effect of host and bacterial treatments. It appears that both the host attributes and the native gut-symbionts drive oviposition preference towards green olives in B. oleae. Moreover, both bacterial treatments and hosts significantly affected the development of B. oleae larvae. Though grapes elicited as many oviposition attempts as green olives, they yielded no pupae. Taken together, our results suggest that the intimate association between B. oleae and their gut-microbes, extends beyond nutritional support to behaviour.
Maori, E. ; Garbian, Y. ; Kunik, V. ; Mozes-Koch, R. ; Malka, O. ; Kalev, H. ; Sabath, N. ; Sela, I. ; Shafir, S. A Transmissible RNA Pathway in Honey Bees. Cell Rep 2019, 27, 1949-1959.e6.Abstract
Systemic RNAi, initiated by double-stranded RNA (dsRNA) ingestion, has been reported in diverse invertebrates, including honey bees, demonstrating environmental RNA uptake that undermines homologous gene expression. However, the question why any organism would take up RNA from the environment has remained largely unanswered. Here, we report on horizontal RNA flow among honey bees mediated by secretion and ingestion of worker and royal jelly diets. We demonstrate that transmission of jelly-secreted dsRNA to larvae is biologically active and triggers gene knockdown that lasts into adulthood. Worker and royal jellies harbor differential naturally occurring RNA populations. Jelly RNAs corresponded to honey bee protein-coding genes, transposable elements, and non-coding RNA, as well as bacteria, fungi, and viruses. These results reveal an inherent property of honey bees to share RNA among individuals and generations. Our findings suggest a transmissible RNA pathway, playing a role in social immunity and signaling between members of the hive.
Dekel, A. ; Yakir, E. ; Bohbot, J. D. The sulcatone receptor of the strict nectar-feeding mosquito Toxorhynchites amboinensis. Insect Biochemistry and Molecular Biology 2019, 111, 103174. Publisher's VersionAbstract
Controlling Ae. aegypti populations and the prevention of mosquito bites includes the development of monitoring, repelling and attract-and-kill strategies that are based on understanding the chemical ecology of these pests. Olfactory-mediated attraction to mammals has recently been linked to the mosquito Aedes aegypti odorant receptor Or4, which is activated by animal-released 6-Methyl-5-hepten-2-one (sulcatone). This odorant is also a major component of flower scents and may play a role outside animal-host seeking. To explore the role of this chemical cue, we looked at the interaction between sulcatone and an Or4 homolog expressed in the antennae of the strict nectar-feeding mosquito Toxorhynchites amboinensis. Using the two-electrode voltage clamp of Xenopus oocytes as a heterologous expression system, we show that this receptor is a high intensity sulcatone receptor comparable to its Aedes counterparts. We also show that OR4 is activated by other aliphatic ketones and is inhibited by DEET. This pharmacological characterization suggests that sulcatone may be operating in more than one context in the Culicidae family.
Nash, A. ; Urdaneta, G. M. ; Beaghton, A. K. ; Hoermann, A. ; Papathanos, P. A. ; Christophides, G. K. ; Windbichler, N. Integral gene drives for population replacement. Biol Open 2019, 8.Abstract
A first generation of CRISPR-based gene drives has now been tested in the laboratory in a number of organisms, including malaria vector mosquitoes. Challenges for their use in the area-wide genetic control of vector-borne disease have been identified, including the development of target site resistance, their long-term efficacy in the field, their molecular complexity, and practical and legal limitations for field testing of both gene drive and coupled anti-pathogen traits. We have evaluated theoretically the concept of integral gene drive (IGD) as an alternative paradigm for population replacement. IGDs incorporate a minimal set of molecular components, including drive and anti-pathogen effector elements directly embedded within endogenous genes - an arrangement that in theory allows targeting functionally conserved coding sequences without disrupting their function. Autonomous and non-autonomous IGD strains could be generated, optimized, regulated and imported independently. We performed quantitative modeling comparing IGDs with classical replacement drives and show that selection for the function of the hijacked host gene can significantly reduce the establishment of resistant alleles in the population, while drive occurring at multiple genomic loci prolongs the duration of transmission blockage in the face of pre-existing target site variation. IGD thus has potential as a more durable and flexible population replacement strategy.
Ruel, D. ; Yakir, E. ; Bohbot, J. D. Supersensitive Odorant Receptor Underscores Pleiotropic Roles of Indoles in Mosquito Ecology. Frontiers in Cellular Neuroscience 2019, 12, 533. Publisher's VersionAbstract
Mosquitoes exhibit highly diverse and fast evolving odorant receptors. The indole-sensitive odorant receptor gene clade, comprised of Or2 and Or10 is a notable exception on account of its conservation in both mosquito subfamilies. This group of paralogous genes exhibits a complex developmental expression pattern in Aedes aegypti: AaegOr2 is expressed in both adults and larvae, AaegOr10 is adult-specific and a third member named AaegOr9 is larva-specific. OR2 and OR10 have been deorphanized and are selectively activated by indole and skatole, respectively. Using the two-electrode voltage clamp of Xenopus oocytes expressing Ae. aegypti ORs, we show that AaegOR9 is supersensitive and narrowly tuned to skatole. Our findings suggest that Ae. aegypti has evolved two distinct molecular strategies to detect skatole in aquatic and terrestrial environments, highlighting the central ecological roles of indolic compounds in the evolutionary and life histories of these insects.
Dekel, A. ; Yakir, E. ; Bohbot, J. D. The evolutionarily conserved indolergic receptors of the non-hematophagous elephant mosquito Toxorhynchites amboinensis. Insect Biochemistry and Molecular Biology 2019, 110, 45 - 51. Publisher's VersionAbstract
The conservation of the mosquito indolergic receptors across the Culicinae and Anophelinae mosquito lineages, which spans 200 million years of evolution, is a testament to the central role of indolic compounds in the biology of these insects. Indole and skatole have been associated with the detection of oviposition sites and animal hosts. To evaluate the potential ecological role of these two compounds, we have used a pharmacological approach to characterize homologs of the indolergic receptors Or2 and Or10 in the non-hematophagous elephant mosquito Toxorhynchites amboinensis. We provide evidence that both receptors are narrowly tuned to indole and skatole like their counterparts from hematophagous mosquitoes. These findings indicate that Toxorhynchites detects indole and skatole in an ecological context to be determined and underscore the importance of understanding the role of these compounds in mosquitoes.
Lotan, A. ; Kost, R. ; Mandelik, Y. ; Peled, Y. ; Chakuki, D. ; Shamir, S. Z. ; Ram, Y. National scale mapping of ecosystem services in Israel - Genetic resources, pollination and cultural services. One Ecosystem 2018, 3. Publisher's VersionAbstract
The Israel - National Ecosystem Assessment (I-NEA) project aims to present a comprehensive picture of the state and trends of Israel’s ecosystem services across all ecosystems, by integrating existing data and information collected from a wide range of sources. Although there is a lack of information about the spatial distribution of ecosystem services’ provisioning in Israel, their mapping constitutes an important part of the assessment. In this paper, we present a national-scale mapping of three ecosystem services, each of them implemented using different methods: 1) Genetic resources service, mapped using spatial observations of the Crop Wild Relatives species; 2) potential of pollination service, which is provided by wild bees, mapped using an expert-based habitat model related to land use and land cover; and 3) cultural service of recreation, mapped by analysing the distribution of geotagged digital photographs uploaded to social media resources. The derived maps visualise, for the first time in Israel, the spatially distributed values of the three ecosystem services. Supply hotspots with high values for all three services were identified, as well as spatial differences amongst the ecosystem services. These nationalscale maps provide overlooked insights and can be very useful for strategic discussions of stakeholders and decision-makers but should be regarded with caution given existing knowledge gaps and possible inaccuracies due to data scarcity and low resolution. © Lotan A et al.
Wright, G. A. ; Nicolson, S. W. ; Shafir, S. Nutritional Physiology and Ecology of Honey Bees. Annu Rev Entomol 2018, 63, 327-344.Abstract
Honey bees feed on floral nectar and pollen that they store in their colonies as honey and bee bread. Social division of labor enables the collection of stores of food that are consumed by within-hive bees that convert stored pollen and honey into royal jelly. Royal jelly and other glandular secretions are the primary food of growing larvae and of the queen but are also fed to other colony members. Research clearly shows that bees regulate their intake, like other animals, around specific proportions of macronutrients. This form of regulation is done as individuals and at the colony level by foragers.
Papathanos, P. A. ; Windbichler, N. Redkmer: An Assembly-Free Pipeline for the Identification of Abundant and Specific X-Chromosome Target Sequences for X-Shredding by CRISPR Endonucleases. The CRISPR journal 2018, 1 88 - 98. Publisher's VersionAbstract
CRISPR-based synthetic sex ratio distorters, which operate by shredding the X-chromosome during male meiosis, are promising tools for the area-wide control of harmful insect pest or disease vector species. X-shredders have been proposed as tools to suppress insect populations by biasing the sex ratio of the wild population toward males, thus reducing its natural reproductive potential. However, to build synthetic X-shredders based on CRISPR, the selection of gRNA targets, in the form of high-copy sequence repeats on the X chromosome of a given species, is difficult, since such repeats are not accurately resolved in genome assemblies and cannot be assigned to chromosomes with confidence. We have therefore developed the redkmer computational pipeline, designed to identify short and highly abundant sequence elements occurring uniquely on the X chromosome. Redkmer was designed to use as input minimally processed whole genome sequence data from males and females. We tested redkmer with short- and long-read whole genome sequence data of Anopheles gambiae, the major vector of human malaria, in which the X-shredding paradigm was originally developed. Redkmer established long reads as chromosomal proxies with excellent correlation to the genome assembly and used them to rank X-candidate kmers for their level of X-specificity and abundance. Among these, a high-confidence set of 25-mers was identified, many belonging to previously known X-chromosome repeats of Anopheles gambiae, including the ribosomal gene array and the selfish elements harbored within it. Data from a control strain, in which these repeats are shared with the Y chromosome, confirmed the elimination of these kmers during filtering. Finally, we show that redkmer output can be linked directly to gRNA selection and off-target prediction. In addition, the output of redkmer, including the prediction of chromosomal origin of single-molecule long reads and chromosome specific kmers, could also be used for the characterization of other biologically relevant sex chromosome sequences, a task that is frequently hampered by the repetitiveness of sex chromosome sequence content.
Waters, A. J. ; Capriotti, P. ; Gaboriau, D. C. A. ; Papathanos, P. A. ; Windbichler, N. Rationally-engineered reproductive barriers using CRISPR & CRISPRa: an evaluation of the synthetic species concept in Drosophila melanogaster. 2018, 8 13125. Publisher's VersionAbstract
The ability to erect rationally-engineered reproductive barriers in animal or plant species promises to enable a number of biotechnological applications such as the creation of genetic firewalls, the containment of gene drives or novel population replacement and suppression strategies for genetic control. However, to date no experimental data exist that explores this concept in a multicellular organism. Here we examine the requirements for building artificial reproductive barriers in the metazoan model Drosophila melanogaster by combining CRISPR-based genome editing and transcriptional transactivation (CRISPRa) of the same loci. We directed 13 single guide RNAs (sgRNAs) to the promoters of 7 evolutionary conserved genes and used 11 drivers to conduct a misactivation screen. We identify dominant-lethal activators of the eve locus and find that they disrupt development by strongly activating eve outside its native spatio-temporal context. We employ the same set of sgRNAs to isolate, by genome editing, protective INDELs that render these loci resistant to transactivation without interfering with target gene function. When these sets of genetic components are combined we find that complete synthetic lethality, a prerequisite for most applications, is achievable using this approach. However, our results suggest a steep trade-off between the level and scope of dCas9 expression, the degree of genetic isolation achievable and the resulting impact on fly fitness. The genetic engineering strategy we present here allows the creation of single or multiple reproductive barriers and could be applied to other multicellular organisms such as disease vectors or transgenic organisms of economic importance.
Papathanos, P. A. ; Bourtzis, K. ; Tripet, F. ; Bossin, H. ; Virginio, J. F. ; Capurro, M. L. ; Pedrosa, M. C. ; Guindo, A. ; Sylla, L. ; Coulibaly, M. B. ; et al. A perspective on the need and current status of efficient sex separation methods for mosquito genetic control. Parasit Vectors 2018, 11, 654.Abstract
Major efforts are currently underway to develop novel, complementary methods to combat mosquito-borne diseases. Mosquito genetic control strategies (GCSs) have become an increasingly important area of research on account of their species-specificity, track record in targeting agricultural insect pests, and their environmentally non-polluting nature. A number of programs targeting Aedes and Anopheles mosquitoes, vectors of human arboviruses and malaria respectively, are currently being developed or deployed in many parts of the world. Operationally implementing these technologies on a large scale however, beyond proof-of-concept pilot programs, is hampered by the absence of adequate sex separation methods. Sex separation eliminates females in the laboratory from male mosquitoes prior to release. Despite the need for sex separation for the control of mosquitoes, there have been limited efforts in recent years in developing systems that are fit-for-purpose. In this special issue of Parasites and Vectors we report on the progress of the global Coordinated Research Program on "Exploring genetic, molecular, mechanical and behavioural methods for sex separation in mosquitoes" that is led by the Insect Pest Control Subprogramme of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture with the specific aim of building efficient sex separation systems for mosquito species. In an effort to overcome current barriers we briefly highlight what we believe are the three main reasons why progress has been so slow in developing appropriate sex separation systems: the availability of methods that are not scalable, the difficulty of building the ideal genetic systems and, finally, the lack of research efforts in this area.
Eakteiman, G. ; Moses-Koch, R. ; Moshitzky, P. ; Mestre-Rincon, N. ; Vassão, D. G. ; Luck, K. ; Sertchook, R. ; Malka, O. ; Morin, S. Targeting detoxification genes by phloem-mediated RNAi: A new approach for controlling phloem-feeding insect pests. Insect Biochem Mol Biol 2018, 100, 10-21.Abstract
Many phloem-feeding insects are considered severe pests of agriculture and are controlled mainly by chemical insecticides. Continued extensive use of these inputs is environmentally undesirable, and also leads to the development of insecticide resistance. Here, we used a plant-mediated RNA interference (RNAi) approach, to develop a new control strategy for phloem-feeding insects. The approach aims to silence "key" detoxification genes, involved in the insect's ability to neutralize defensive and toxic plant chemistry. We targeted a glutathione S-transferase (GST) gene, BtGSTs5, in the phloem-feeding whitefly Bemisia tabaci, a devastating global agricultural pest. We report three major findings. First, significant down regulation of the BtGSTs5 gene was obtained in the gut of B. tabaci when the insects were fed on Arabidopsis thaliana transgenic plants expressing dsRNA against BtGSTs5 under a phloem-specific promoter. This brings evidence that phloem-feeding insects can be efficiently targeted by plant-mediated RNAi. Second, in-silico and in-vitro analyses indicated that the BtGSTs5 enzyme can accept as substrates, hydrolyzed aliphatic- and indolic-glucosinolates, and produce their corresponding detoxified conjugates. Third, performance assays suggested that the BtGSTs5 gene silencing prolongs the developmental period of B. tabaci nymphs. Taken together, these findings suggest that BtGSTs5 is likely to play an important role in enabling B. tabaci to successfully feed on glucosinolate-producing plants. Targeting the gene by RNAi in Brassicaceae cropping systems, will likely not eliminate the pest populations from the fields but will significantly reduce their success over the growing season, support prominent activity of natural enemies, eventually allowing the establishment of stable and sustainable agroecosystem.
Santos-Garcia, D. ; Juravel, K. ; Freilich, S. ; Zchori-Fein, E. ; Latorre, A. ; Moya, A. ; Morin, S. ; Silva, F. J. To B or Not to B: Comparative Genomics Suggests as a Source of B Vitamins in Whiteflies. Front Microbiol 2018, 9 2254.Abstract
Insect lineages feeding on nutritionally restricted diets such as phloem sap, xylem sap, or blood, were able to diversify by acquiring bacterial species that complement lacking nutrients. These bacteria, considered obligate/primary endosymbionts, share a long evolutionary history with their hosts. In some cases, however, these endosymbionts are not able to fulfill all of their host's nutritional requirements, driving the acquisition of additional symbiotic species. Phloem-feeding members of the insect family Aleyrodidae (whiteflies) established an obligate relationship with Portiera aleyrodidarum, which provides its hots with essential amino acids and carotenoids. In addition, many whitefly species harbor additional endosymbionts which may potentially further supplement their host's diet. To test this hypothesis, genomes of several endosymbionts of the whiteflies and were analyzed. In addition to , all three species were found to harbor one and one endosymbiont. A comparative analysis of genomes revealed that although all three are capable of synthesizing B vitamins and cofactors, such as pyridoxal, riboflavin, or folate, their genomes and phylogenetic relationship vary greatly. of and belong to the same clade, and display characteristics of facultative endosymbionts, such as large genomes (3 Mb) with thousands of genes and pseudogenes, intermediate GC content, and mobile genetic elements. In contrast, of belongs to a different lineage and displays the characteristics of a primary endosymbiont-a reduced genome (670 kb) with ~400 genes, 32% GC content, and no mobile genetic elements. However, the presence of 274 pseudogenes suggests that this symbiotic association is more recent than other reported primary endosymbionts of hemipterans. The gene repertoire of of is completely integrated in the symbiotic consortia, and the biosynthesis of most vitamins occurs in shared pathways with its host. In addition, endosymbionts have also retained the ability to produce riboflavin, flavin adenine dinucleotide, and folate, and may make a nutritional contribution. Taken together, our results show that hold a pivotal place in whitefly nutrition by their ability to produce B vitamins.
Malka, O. ; Santos-Garcia, D. ; Feldmesser, E. ; Sharon, E. ; Krause-Sakate, R. ; Delatte, H. ; van Brunschot, S. ; Patel, M. ; Visendi, P. ; Mugerwa, H. ; et al. Species-complex diversification and host-plant associations in Bemisia tabaci: A plant-defence, detoxification perspective revealed by RNA-Seq analyses. Mol Ecol 2018, 27, 4241-4256.Abstract
Insect-plant associations and their role in diversification are mostly studied in specialists. Here, we aimed to identify macroevolution patterns in the relationships between generalists and their host plants that have the potential to promote diversification. We focused on the Bemisia tabaci species complex containing more than 35 cryptic species. Mechanisms for explaining this impressive diversification have focused so far on allopatric forces that assume a common, broad, host range. We conducted a literature survey which indicated that species in the complex differ in their host range, with only few showing a truly broad one. We then selected six species, representing different phylogenetic groups and documented host ranges. We tested whether differences in the species expression profiles of detoxification genes are shaped more by their phylogenetic relationships or by their ability to successfully utilize multiple hosts, including novel ones. Performance assays divided the six species into two groups of three, one showing higher performance on various hosts than the other (the lower performance group). The same grouping pattern appeared when the species were clustered according to their expression profiles. Only species placed in the lower performance group showed a tendency to lower the expression of multiple genes. Taken together, these findings bring evidence for the existence of a common detoxification "machinery," shared between species that can perform well on multiple hosts. We raise the possibility that this "machinery" might have played a passive role in the diversification of the complex, by allowing successful migration to new/novel environments, leading, in some cases, to fragmentation and speciation.
Ueckermann, E. A. ; Palevsky, E. ; Gerson, U. ; Recht, E. ; Theron, P. D. The Tenuipalpidae (Acari: Trombidiformes) of Israel. Acarologia 2018, 58, 483-525. Publisher's Version
Arien, Y. ; Dag, A. ; Shafir, S. Omega-6:3 Ratio More Than Absolute Lipid Level in Diet Affects Associative Learning in Honey Bees. Frontiers in Psychology 2018, 9 1001. Publisher's VersionAbstract
Floral pollen is a major source of honey bee nutrition that provides them with micro- and macro-nutrients, including proteins, fatty acids, vitamins, and minerals. Different pollens vary in composition, including in the essential fatty acids, alpha-linolenic acid (omega-3) and linoleic acid (omega-6). Monocultures, prevalent in modern agriculture, may expose honey bee colonies to unbalanced omega-6:3 diets. The importance of omega-3 in the diet for adequate learning and cognitive function, with a focus on suitable omega-6:3 ratio, is well documented in mammals. We have recently shown, for the first time in invertebrates, the importance of omega-3 in diets for associative learning ability in honey bees. In the current work, we examine the effect of the absolute amount of omega-3 in diet compared to the omega-6:3 ratio on honey bee associative learning. We fed newly emerged bees for 1 week on different artificial diets, which had lipid concentration of 1, 2, 4, or 8%, with omega-6:3 ratios of 0.3, 1, or 5, respectively. We then tested the bees in a proboscis-extension response olfactory conditioning assay. We found that both omega-6:3 ratio and total lipid concentration affected learning. The most detrimental diet for learning was that with a high omega-6:3 ratio of 5, regardless of the absolute amount of omega-3 in the diet. Bees fed an omega-6:3 ratio of 1, with 4% total lipid concentration achieved the best performance. Our results with honey bees are consistent with those found in mammals. Best cognitive performance is achieved by a diet that is sufficiently rich in essential fatty acids, but as long as the omega-6:3 ratio is not high.
Topman, S. ; Tamir-Ariel, D. ; Bochnic-Tamir, H. ; Stern Bauer, T. ; Shafir, S. ; Burdman, S. ; Hayouka, Z. Random peptide mixtures as new crop protection agents. Microbial Biotechnology 2018, 11, 1027-1036. Publisher's VersionAbstract
Summary Many types of crops are severely affected by at least one important bacterial disease. Chemical control of bacterial plant diseases in the field vastly relies on copper-based bactericides, yet with limited efficacy. In this study, we explored the potential of two random peptide mixture (RPM) models as novel crop protection agents. These unique peptide mixtures consist of random combination of l-phenylalanine and l- or d-lysine (FK-20 and FdK-20, respectively) along the 20 mer chain length of the peptides. Both RPMs displayed powerful bacteriostatic and bactericidal activities towards strains belonging to several plant pathogenic bacterial genera, for example, Xanthomonas, Clavibacter and Pseudomonas. In planta studies in the glasshouse revealed that RPMs significantly reduced disease severity of tomato and kohlrabi plants infected with Xanthomonas perforans and Xanthomonas campestris pv. campestris respectively. Moreover, RPM effects on reduction in disease severity were similar to those exerted by the commercial copper-based bactericide Kocide 2000 that was applied at a 12-fold higher concentration of the active compound relative to the RPM treatments. Importantly, the two tested RPM compounds had no toxic effect on survival of bees and Caco-2 mammalian cells. This study demonstrates the potential of these innovative RPMs to serve as crop protection agents against crop diseases caused by phytopathogenic bacteria.
Papa, F. ; Windbichler, N. ; Waterhouse, R. M. ; Cagnetti, A. ; D'Amato, R. ; Persampieri, T. ; Lawniczak, M. K. N. ; Nolan, T. ; Papathanos, P. A. Rapid evolution of female-biased genes among four species of Anopheles malaria mosquitoes. Genome research 2017, 27, 1536 - 1548. Publisher's VersionAbstract
Understanding how phenotypic differences between males and females arise from the sex-biased expression of nearly identical genomes can reveal important insights into the biology and evolution of a species. Among Anopheles mosquito species, these phenotypic differences include vectorial capacity, as it is only females that blood feed and thus transmit human malaria. Here, we use RNA-seq data from multiple tissues of four vector species spanning the Anopheles phylogeny to explore the genomic and evolutionary properties of sex-biased genes. We find that, in these mosquitoes, in contrast to what has been found in many other organisms, female-biased genes are more rapidly evolving in sequence, expression, and genic turnover than male-biased genes. Our results suggest that this atypical pattern may be due to the combination of sex-specific life history challenges encountered by females, such as blood feeding. Furthermore, female propensity to mate only once in nature in male swarms likely diminishes sexual selection of post-reproductive traits related to sperm competition among males. We also develop a comparative framework to systematically explore tissue- and sex-specific splicing to document its conservation throughout the genus and identify a set of candidate genes for future functional analyses of sex-specific isoform usage. Finally, our data reveal that the deficit of male-biased genes on the X Chromosomes in Anopheles is a conserved feature in this genus and can be directly attributed to chromosome-wide transcriptional regulation that de-masculinizes the X in male reproductive tissues.
Bernardini, F. ; Galizi, R. ; Wunderlich, M. ; Taxiarchi, C. ; Kranjc, N. ; Kyrou, K. ; Hammond, A. ; Nolan, T. ; Lawniczak, M. N. K. ; Papathanos, P. A. ; et al. Cross-Species Y Chromosome Function Between Malaria Vectors of the Species Complex. Genetics 2017, 207, 729-740.Abstract
Y chromosome function, structure and evolution is poorly understood in many species, including the genus of mosquitoes-an emerging model system for studying speciation that also represents the major vectors of malaria. While the Anopheline Y had previously been implicated in male mating behavior, recent data from the complex suggests that, apart from the putative primary sex-determiner, no other genes are conserved on the Y. Studying the functional basis of the evolutionary divergence of the Y chromosome in the gambiae complex is complicated by complete F1 male hybrid sterility. Here, we used an F1 × F0 crossing scheme to overcome a severe bottleneck of male hybrid incompatibilities that enabled us to experimentally purify a genetically labeled Y chromosome in an background. Whole genome sequencing (WGS) confirmed that the Y retained its original sequence content in the genomic background. In contrast to comparable experiments in , we find that the presence of a heterospecific Y chromosome has no significant effect on the expression of genes, and transcriptional differences can be explained almost exclusively as a direct consequence of transcripts arising from sequence elements present on the Y chromosome itself. We find that Y hybrids show no obvious fertility defects, and no substantial reduction in male competitiveness. Our results demonstrate that, despite their radically different structure, Y chromosomes of these two species of the gambiae complex that diverged an estimated 1.85 MYA function interchangeably, thus indicating that the Y chromosome does not harbor loci contributing to hybrid incompatibility. Therefore, Y chromosome gene flow between members of the gambiae complex is possible even at their current level of divergence. Importantly, this also suggests that malaria control interventions based on sex-distorting Y drive would be transferable, whether intentionally or contingent, between the major malaria vector species.