Medfly-Wolbachia symbiosis: genotype x genotype interactions determine host's life history traits under mass rearing conditions.

BACKGROUND: Wolbachia pipientis is a widespread, obligatory intracellular and maternally inherited bacterium, that induces a wide range of reproductive alterations to its hosts. Cytoplasmic Incompatibility (CI) is causing embryonic lethality, the most common of them. Despite that Wolbachia-borne sterility has been proposed as an environmental friendly pest control method (Incompatible Insect Technique, IIT) since 1970s, the fact that Wolbachia modifies important fitness components of its hosts sets severe barriers to IIT implementation. Mass rearing of Mediterranean fruit fly, Ceratitis capitata (medfly), is highly optimized given that this pest is a model species regarding the implementation of another sterility based pest control method, the Sterile Insect Technique (SIT). We used the medfly-Wolbachia symbiotic association, as a model system, to study the effect of two different Wolbachia strains, on the life history traits of 2 C. capitata lines with different genomic background. RESULTS: Wolbachia effects are regulated by both C. capitata genetic background and the Wolbachia strain. Wolbachia infection reduces fertility rates in both C. capitata genetic backgrounds and shortens the pre-pupa developmental duration in the GSS strain. On the other hand, regardless of the strain of Wolbachia (wCer2, wCer4) infection does not affect either the sex ratio or the longevity of adults. wCer4 infection imposed a reduction in females' fecundity but wCer2 did not. Male mating competitiveness, adults flight ability and longevity under water and food deprivation were affected by both the genetic background of medfly and the strain of Wolbachia (genotype by genotype interaction). CONCLUSION: Wolbachia infection could alter important life history traits of mass-reared C. capitata lines and therefore the response of each genotype on the Wolbachia infection should be considered toward ensuring the productivity of the Wolbachia-infected insects under mass-rearing conditions.

Genetic structure of Mediterranean fruit fly (Diptera: Tephritidae) populations from Turkey revealed by mitochondrial DNA markers.

Ceratitis capitata is one among the most destructive and economically important agricultural pests worldwide. Despite its economic significance, the population structures of this pest have remained relatively unexplored in the eastern Mediterranean basin. Using two mitochondrial markers, the present study aimed to examining the population genetic structure and diversity of C. capitata populations in Turkey, the region that covers a large part of the eastern Mediterranean area. Our results revealed that the Turkish Mediterranean fruit fly populations are characterized by low levels of genetic diversity and limited population differentiation. For comparison purposes, wemerged the sequences identified in the present study with the previously reported sequences from acrossthe world into the data matrix. The haplotype network showed that, unlike the African samples the Mediterranean samples and samples from the new world (America, Pacific region and Australia) did not show any clear pattern of geographical structuring, which indicates that the Mediterranean basin, particularly the eastern Mediterranean region populations, may have played a moreimportant role in the colonization of C. capitata populations to the new world. The results also revealed a close genetic relationship between the Turkish and Iranian populations, suggesting that the Iranian C. capitata populations probably originated from Turkey.

Chromatin immunoprecipitation (ChIP) method for non-model fruit flies (Diptera: Tephritidae) and evidence of histone modifications.

Interactions between DNA and proteins located in the cell nucleus play an important role in controlling physiological processes by specifying, augmenting and regulating context-specific transcription events. Chromatin immunoprecipitation (ChIP) is a widely used methodology to study DNA-protein interactions and has been successfully used in various cell types for over three decades. More recently, by combining ChIP with genomic screening technologies and Next Generation Sequencing (e.g. ChIP-seq), it has become possible to profile DNA-protein interactions (including covalent histone modifications) across entire genomes. However, the applicability of ChIP-chip and ChIP-seq has rarely been extended to non-model species because of a number of technical challenges. Here we report a method that can be used to identify genome wide covalent histone modifications in a group of non-model fruit fly species (Diptera: Tephritidae). The method was developed by testing and refining protocols that have been used in model organisms, including Drosophila melanogaster. We demonstrate that this method is suitable for a group of economically important pest fruit fly species, viz., Bactrocera dorsalis, Ceratitis capitata, Zeugodacus cucurbitae and Bactrocera tryoni. We also report an example ChIP-seq dataset for B. tryoni, providing evidence for histone modifications in the genome of a tephritid fruit fly for the first time. Since tephritids are major agricultural pests globally, this methodology will be a valuable resource to study taxa-specific evolutionary questions and to assist with pest management. It also provides a basis for researchers working with other non-model species to undertake genome wide DNA-protein interaction studies.

Mediterranean fruit fly on Mimusops zeyheri indigenous to South Africa: a threat to the horticulture industry.

BACKGROUND: Claims abound that the Transvaal red milkwood, Mimusops zeyheri, indigenous to areas with tropical and subtropical commercial fruit trees and fruiting vegetables in South Africa, is relatively pest free owing to its copious concentrations of latex in the above-ground organs. On account of observed fruit fly damage symptoms, a study was conducted to determine whether M. zeyheri was a host to the notorious quarantined Mediterranean fruit fly (Ceratitis capitata). RESULTS: Fruit samples were kept for 16-21 days in plastic pots containing moist steam-pasteurised growing medium with tops covered with a mesh sheath capable of retaining emerging flies. Microscopic diagnosis of the trapped flies suggested that the morphological characteristics were congruent with those of C. capitata, which was confirmed through cytochrome c oxidase I (COI) gene sequence alignment with a 100% bootstrap value and 99% confidence probability when compared with those from the National Centre for Biotechnology Information database. CONCLUSION: This study demonstrated that M. zeyheri is a host of C. capitata. Therefore, C. capitata from infestation reservoirs of M. zeyheri fruit trees could be a major threat to the tropical and subtropical fruit industries in South Africa owing to the fruit-bearing nature of the new host. © 2015 Society of Chemical Industry.

Population genetics of Ceratitis capitata in South Africa: implications for dispersal and pest management.

The invasive Mediterranean fruit fly (medfly), Ceratitis capitata, is one of the major agricultural and economical pests globally. Understanding invasion risk and mitigation of medfly in agricultural landscapes requires knowledge of its population structure and dispersal patterns. Here, estimates of dispersal ability are provided in medfly from South Africa at three spatial scales using molecular approaches. Individuals were genotyped at 11 polymorphic microsatellite loci and a subset of individuals were also sequenced for the mitochondrial cytochrome oxidase subunit I gene. Our results show that South African medfly populations are generally characterized by high levels of genetic diversity and limited population differentiation at all spatial scales. This suggests high levels of gene flow among sampling locations. However, natural dispersal in C. capitata has been shown to rarely exceed 10 km. Therefore, documented levels of high gene flow in the present study, even between distant populations (>1600 km), are likely the result of human-mediated dispersal or at least some form of long-distance jump dispersal. These findings may have broad applicability to other global fruit production areas and have significant implications for ongoing pest management practices, such as the sterile insect technique.

Cloning, sequence identification and expression profile analysis of α-L-fucosidase gene from the Mediterranean fruit fly Ceratitis capitata.

The Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae) is one of the most destructive agricultural pests, a polyphagus insect of relevant economic importance and is widespread in many regions around the world. It is the best-studied fruit fly pest at genetic and molecular level and much has been learned on its ecology and behaviour. An α-L-fucosidase has been recently hypothesized to be involved in sperm-egg interactions in Drosophila melanogaster and in other Drosophila species. Here, a complete cDNA encoding a putative α-L-fucosidase of the medfly was amplified using the reverse polymerase chain reaction (RT-PCR) with degenerate based on the conserved coding sequence information of several insect α-L-fucosidases, cloned and sequenced (GenBank accession no. FJ177429). The coding region consisted of 1482 bp which encoded a 485-residues protein (named CcFUCA) with a predicted molecular mass of 56.1 kDa. The deduced protein sequence showed 75% amino acid identity to D. melanogaster α-L-fucosidase, and in fact the phylogenetic tree analysis revealed that CcFUCA had closer relationships with the α-L-fucosidases of drosophilid species. The tissue expression analysis indicated that CcFuca was expressed in a single transcript in all tissues, suggesting a ubiquitous localization pattern of the encoded protein. Our findings provide novel insights on a gene encoding a protein potentially involved in primary gamete interactions in C. capitata.

Biodemography of the Mediterranean fruit fly: aging, longevity and adaptation in the wild.

The purpose of this paper is to summarize recent research on longevity, aging and adaptation in wild medfly populations and in a close relative of the medfly. The key findings include a new life table identity that relates age structure and the distribution of deaths in stationary populations, seasonal variation in the post-capture longevity of trapped medflies of unknown age, greater longevity of once-wild (wild-caught) adult medflies relative to never-wild (laboratory-emerged) individuals, differences in age specificity of different medfly field capture methods, large variation in the sex-specific longevity of six medfly global biotypes (e.g. Kenya; Brazil; Greece), and the extraordinary longevity of the natal fruit fly - a sister species of the medfly. The discussion contains a listing of discoveries derived from this recent research that appear to be unique to the investigations on medfly aging in the wild. It is suggested that studies of aging in wild populations of Drosophila melanogaster have the potential to exploit this model organism in an entirely new aging research domain and thus complement the already deep literature on aging in this species.

Molecular taxonomic identification of Dacus and Ceratitis species from Sub-Saharan Africa using mitochondrial haplotypes.

Several different taxa within the genera Dacus and Ceratitis (Diptera: Tephritidae) are important agricultural pests in Sub-Saharan Africa. Although the status of many of these taxa as distinct species and their phylogenetic relationships is unclear, it is clear that these pests use a wide range of host plants and are highly invasive. The great potential for economic damage inflicted by these pests requires the ability to make accurate and reliable taxonomic identification of specimens. However, many limitations and uncertainties are encountered when these species are examined using traditional approaches based on morphological identification techniques. We describe here the amplification and analysis of DNA sequences from the mitochondrial cytochrome oxidase II (COII)-tRNA(lys)-tRNA(ASP) genes from individuals of various Dacus and Ceratitis species and populations from Sub-Saharan Africa. The variation detected in the DNA sequences of these individuals is used both for clarification of their taxonomic status and the analysis of phylogenetic relationships of these taxa.

Isolation and characterization of microsatellite markers from the Mediterranean fruit fly, Ceratitis capitata: cross-species amplification in other Tephritidae species reveals a varying degree of transferability.

The Mediterranean fruit fly, Ceratitis capitata, is a pest of major economic importance and has become a model for the development of SIT control programs for insect pests. Significant information has been accumulated on classical and population genetics of this species during the past 2 decades. However, the availability of molecular markers is limited. Here, we present the isolation and characterization of 159 microsatellite clones and the development of 108 polymorphic microsatellite markers for this insect pest. Mapping by in situ hybridization to polytene chromosomes of 21 microsatellite clones enriched the cytogenetic map that was previously constructed by our group. The enriched map provides a large number of STSs for future genome mapping projects. Cross-species amplification of these microsatellite loci in 12 Tephritidae species and sequence analysis of several amplification products indicated a varying degree of transferability and their possible usefulness as molecular and genetic markers in these species where genetic and molecular tools are limited.

Genetic differentiation, gene flow and the origin of infestations of the medfly, Ceratitis capitata.

The genetic structure of natural populations of the economically important dipteran species Ceratitis capitata was analysed using both biochemical and molecular markers. This revealed considerable genetic variation in populations from different geographic regions. The nature of this variation suggests that the evolutionary history of the species involved the spread of individuals from the ancestral African populations through Europe and, more recently, to Latin America, Hawaii and Australia. The observed variation can be explained by various evolutionary forces acting differentially in the different geographic areas, including genetic drift, bottleneck effects, selection and gene flow. The analysis of the intrinsic variability of the medfly's genome and the genetic relationships among populations of this pest is a prerequisite for any control programme.

Developmental profiles and ecdysone regulation of the mRNAs for two ecdysone receptor isoforms in the Mediterranean fruit fly Ceratitis capitata.

Using 5' RACE with specific primers for the ecdysone receptor B1 isoform of the Mediterranean fruit fly (medfly), Ceratitis capitata, we isolated a cDNA clone encoding the specific region of the medfly ecdysone receptor A isoform (CcEcR-A). The CcEcR-A-specific region was very similar to the EcR-A-specific region of Drosophila melanogaster and less similar to the EcR-A-specific regions of Lepidoptera. The developmental expression of both CcEcR-A and CcEcR-B1 mRNAs was studied in whole animals, salivary glands and ovaries by RT-PCR, using isoform-specific primers. Both CcEcR mRNAs are present in very early embryos, decrease to very low levels during the first hours of embryogenesis and are highly expressed in all consequent embryonic stages. During metamorphosis both isoforms are present showing two peaks; the first at the larval-prepupal transition and the second during the second half of prepupal development. These peaks are correlated with the two puffing cycles and the two major 20-hydroxyecdysone (20E) increases that occur during medfly metamorphosis. CcEcR-B1 mRNA was directly induced in larval salivary glands in vitro by 20E, even at very low concentrations of the hormone, while CcEcR-A mRNA was slightly induced only by high 20E concentrations and in the absence of a protein synthesis inhibitor. During oogenesis, the CcEcR mRNAs were expressed synchronously, peaking at the beginning of both previtellogenic and vitellogenic phases.