A standard cytogenetic map of Culex quinquefasciatus polytene chromosomes in application for fine-scale physical mapping

BACKGROUND: Southern house mosquito Culex quinquefasciatus belongs to the C. pipiens cryptic species complex, with global distribution and unclear taxonomy. Mosquitoes of the complex can transmit human and animal pathogens, such as filarial worm, West Nile virus and avian malarial Plasmodium. Physical gene mapping is crucial to understanding genome organization, function, and systematic relationships of cryptic species, and is a basis for developing new vector control strategies. However, physical mapping was not established previously for Culex due to the lack of well-structured polytene chromosomes. METHODS: Inbreeding was used to diminish inversion polymorphism and asynapsis of chromosomal homologs. Identification of larvae of the same developmental stage using the shape of imaginal discs allowed achievement of uniformity in chromosomal banding pattern. This together with high-resolution phase-contrast photography enabled the development of a cytogenetic map. Fluorescent in situ hybridization was used for gene mapping. RESULTS: A detailed cytogenetic map of C. quinquefasciatus polytene chromosomes was produced. Landmarks for chromosome recognition and cytological boundaries for two inversions were identified. Locations of 23 genes belonging to 16 genomic supercontigs, and 2 cDNA were established. Six supercontigs were oriented and one was found putatively misassembled. The cytogenetic map was linked to the previously developed genetic linkage groups by corresponding positions of 2 genetic markers and 10 supercontigs carrying genetic markers. Polytene chromosomes were numbered according to the genetic linkage groups. CONCLUSIONS: This study developed a new standard cytogenetic photomap of the polytene chromosomes for C. quinquefasciatus and was applied for the fine-scale physical mapping. It allowed us to infer chromosomal position of 1333 of annotated genes belonging to 16 genomic supercontigs and find orientation of 6 of these supercontigs; the new cytogenetic and previously developed genetic linkage maps were integrated based on 12 matches. The map will further assist in finding chromosomal position of the medically important and other genes, contributing into improvement of the genome assembly. Better assembled C. quinquefasciatus genome can serve as a reference for studying other vector species of C. pipiens complex and will help to resolve their taxonomic relationships. This, in turn, will contribute into future development of vector and disease control strategies. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-015-0912-4) contains supplementary material, which is available to authorized users

GGR Biennial Critical Review: Analytical Developments Since 2014

© 2017 The Authors. Geostandards and Geoanalytical Research © 2017 International Association of Geoanalysts This GGR biennial critical review covers developments and innovations in key analytical methods published since January 2014, relevant to the chemical, isotopic and crystallographic characterisation of geological and environmental materials. In nine selected analytical fields, publications considered to be of wide significance are summarised, background information is provided and their importance evaluated. In addition to instrumental technologies, this review also presents a summary of new developments in the preparation and characterisation of rock, microanalytical and isotopic reference materials, including a précis of recent changes and revisions to ISO guidelines for reference material characterisation and reporting. Selected reports are provided of isotope ratio determinations by both solution nebulisation MC-ICP-MS and laser ablation-ICP-MS, as well as of radioactive isotope geochronology by LA-ICP-MS. Most of the analytical techniques elaborated continue to provide new applications for geochemical analysis; however, it is noted that instrumental neutron activation analysis has become less popular in recent years, mostly due to the reduced availability of nuclear reactors to act as a neutron source. Many of the newer applications reported here provide analysis at increasingly finer resolution. Examples include atom probe tomography, a very sensitive method providing atomic scale information, nanoscale SIMS, for isotopic imaging of geological and biological samples, and micro-XRF, which has a spatial resolution many orders of magnitude smaller than conventional XRF