Transcriptional variation of sensory-related genes in natural populations of Aedes albopictus

BACKGROUND: The Asian tiger mosquito, Aedes albopictus, is a highly dangerous invasive vector of numerous medically important arboviruses including dengue, chikungunya and Zika. In four decades it has spread from tropical Southeast Asia to many parts of the world in both tropical and temperate climes. The rapid invasion process of this mosquito is supported by its high ecological and genetic plasticity across different life history traits. Our aim was to investigate whether wild populations, both native and adventive, also display transcriptional genetic variability for functions that may impact their biology, behaviour and ability to transmit arboviruses, such as sensory perception. RESULTS: Antennal transcriptome data were derived from mosquitoes from a native population from Ban Rai, Thailand and from three adventive Mediterranean populations: Athens, Greece and Arco and Trento from Italy. Clear inter-population differential transcriptional activity was observed in different gene categories related to sound perception, olfaction and viral infection. The greatest differences were detected between the native Thai and the Mediterranean populations. The two Italian populations were the most similar. Nearly one million quality filtered SNP loci were identified. CONCLUSION: The ability to express this great inter-population transcriptional variability highlights, at the functional level, the remarkable genetic flexibility of this mosquito species. We can hypothesize that the differential expression of genes, including those involved in sensory perception, in different populations may enable Ae. albopictus to exploit different environments and hosts, thus contributing to its status as a global vector of arboviruses of public health importance. The large number of SNP loci present in these transcripts represents a useful addition to the arsenal of high-resolution molecular markers and a resource that can be used to detect selective pressure and adaptive changes that may have occurred during the colonization process

Genetic Structure and Inferences on Potential Source Areas for Bactrocera dorsalis (Hendel) Based on Mitochondrial and Microsatellite Markers

Bactrocera dorsalis (Diptera: Tephritidae) is mainly distributed in tropical and subtropical Asia and in the Pacific region. Despite its economic importance, very few studies have addressed the question of the wide genetic structure and potential source area of this species. This pilot study attempts to infer the native region of this pest and its colonization pathways in Asia. Combining mitochondrial and microsatellite markers, we evaluated the level of genetic diversity, genetic structure, and the gene flow among fly populations collected across Southeast Asia and China. A complex and significant genetic structure corresponding to the geographic pattern was found with both types of molecular markers. However, the genetic structure found was rather weak in both cases, and no pattern of isolation by distance was identified. Multiple long-distance dispersal events and miscellaneous host selection by this species may explain the results. These complex patterns may have been influenced by human-mediated transportation of the pest from one area to another and the complex topography of the study region. For both mitochondrial and microsatellite data, no signs of bottleneck or founder events could be identified. Nonetheless, maximal genetic diversity was observed in Myanmar, Vietnam and Guangdong (China) and asymmetric migration patterns were found. These results provide indirect evidence that the tropical regions of Southeast Asia and southern coast of China may be considered as the native range of the species and the population expansion is northward. Yunnan (China) is a contact zone that has been colonized from different sources. Regions along the southern coast of Vietnam and China probably served to colonize mainly the southern region of China. Southern coastal regions of China may also have colonized central parts of China and of central Yunnan

De Novo assembly and transcriptome analysis of the mediterranean fruit fly ceratitis capitata early embryos

The agricultural pest Ceratitis capitata, also known as the Mediterranean fruit fly or Medfly, belongs to the Tephritidae family, which includes a large number of other damaging pest species. The Medfly has been the first non-drosophilid fly species which has been genetically transformed paving the way for designing geneticbased pest control strategies. Furthermore, it is an experimentally tractable model, in which transient and transgene-mediated RNAi have been successfully used. We applied Illumina sequencing to total RNA preparations of 8-10 hours old embryos of C. capitata, This developmental window corresponds to the blastoderm cellularization stage. In summary, we assembled 42,614 transcripts which cluster in 26,319 unique transcripts of which 11,045 correspond to protein coding genes; we identified several hundreds of long ncRNAs; we found an enrichment of transcripts encoding RNA binding proteins among the highly expressed transcripts, such as CcTRA-2, known to be necessary to establish and, most likely, to maintain female sex of C. capitata. Our study is the first de novo assembly performed for Ceratitis capitata based on Illumina NGS technology during embryogenesis and it adds novel data to the previously published C. capitata EST databases. We expect that it will be useful for a variety of applications such as gene cloning and phylogenetic analyses, as well as to advance genetic research and biotechnological applications in the Medfly and other related Tephritidae

Novel Discoveries in the Male Accessory Secretions of the Tsetse fly (A transcriptomic/proteomic analysis)

Tsetse flies are the sole vectors of the human and animal forms of African Trypanosomiasis, neglected diseases that affect the health and development of marginalized populations in sub-Saharan Africa. Vector population control is one of the primary methods to prevent trypanosomiasis transmission. However, little is known about the reproductive biology of tsetse flies. A particularly important aspect of tsetse reproductive biology, male seminal secretions, remains unstudied. Based upon the knowledge derived from other insects such as Drosophila and various mosquito species, the proteins contained within these secretions play an important roles in regulating sperm storage, sperm motility, sperm competition, female sexual receptivity, egg production, ovulation, reproductive tract morphology, feeding behavior and other aspects of fly biology. To establish a foothold on this aspect of tsetse reproductive biology, we undertook a project to sequence the transcriptome of the male accessory tissue in tsetse and to sequence the proteome of the male seminal secretions found within the female after mating. Material for transcriptomic analysis was derived from dissected adult male reproductive tracts at different time points. Samples were collected from teneral, 3 day old (reproductively mature), and 6-8 hours post mating male flies. Male reproductive tracts were dissected into two fractions, testes and accessory glands. RNA isolated from these samples was used to construct 6 illumina libraries which were sequenced using paired end sequencing technology. To complement the transcriptomes, samples of male produced spermatophores were collected for proteomic analysis from the uterus of newly mated female flies. Protein samples were analyzed by LC-MS/MS. Male accessory and testes illumina sequencing data was analyzed to identify the most abundant transcripts within each library, compared between libraries to identify temporal and tissue specific differential expression patterns and compared with transcriptome data from adult female flies to identify male specific transcripts. The results of these analyses were then compared with the proteomic data to confirm transcriptomic predictions of secreted accessory proteins and identify additional unpredicted proteins. Analysis of these data sets resulted in the identification of a novel set of male accessory genes/proteins. Our initial analysis has identified a total of 25 putative accessory gland proteins via cross referencing our tissue specific transcriptome and the spermatophore proteome. Of these proteins, only one of the predicted genes (a serine protease inhibitor from the BPTI/Kunitz family) is orthologus to an accessory protein identified within Drosophila. Many proteins identified are tsetse specific and novel. Three of these novel proteins are the most abundant proteins in the spermatophore. These three proteins form a novel tsetse specific gene family that appears to have arisen through tandem gene duplication events. Further functional analysis will be required to identify the role that these novel proteins play in tsetse reproductive physiology. However, while many of the proteins we have identified are not true orthologs to other characterized accessory proteins, their function appears to have remained orthologus to those of accessory proteins from other Dipteran species. These functions include serine protease inhibitors, odorant binding proteins, antioxidants, immune proteins, glycoproteins, endocuticle proteins and sperm binding proteins

A fluorescent sperm-specific marker for the medfly, Ceratitis capitata.

The medfly, Ceratitis capitata (Diptera: Tephritidae) is an invasive pest species of agricultural importance. Its polyphagous behavior and its high reproductive capacity are responsible for the spread of this species in the last two centuries from sub-Saharan Africa to several tropical and sub-tropical regions worldwide. The environmental-friendly Sterile Insect Technique (SIT) has been effectively applied as a component of area-wide integrated pest management (AW-IPM) for C. capitata since the 1970s. Effective monitoring to assess the number and mating success of the released medflies is essential. Using a transgenic approach we developed a direct sperm visualization system which makes it possible to follow the fate of sperm from different males in the female reproductive tract of the medfly. For this purpose, we generated a sperm-specific marking system based on the spermatogenesis-specific C. capitata beta2-tubulin (Ccbeta2t) promoter driving the expression of the reporter genes GFP or DsRed. Monitoring of the mating success of sterile released males by trapping females and examining their spermathecae is possible with these strains. Moreover, the availability of differently sperm-marked lines will help us to understand the relationship between sperm allocation, remating frequency and sperm displacement in the medfly, given that in wild populations females can remate with a strong paternity skew. In preliminary laboratory competitiveness assays we determined that the marker does not cause general fitness disadvantages. Therefore, such harmless transgenic markers represent an ideal springboard to transfer insect transgenesis technology from the laboratory to field applications