Asymmetric Phenotypes of Sterile Hybrid Males From Reciprocal Crosses Between Species of the Anopheles gambiae Complex

Haldane’s rule of speciation states that sterility or inviability affects the heterogametic sex of inter-species hybrids. Darwin’s corollary to Haldane’s rule implies that there are asymmetric phenotypes in inter-species hybrids from reciprocal crosses. Studying the phenotypes of F1 hybrids among closely related species of malaria mosquitoes can assist researchers in identifying the genetic factors and molecular mechanisms of speciation. To characterize phenotypes of sterile hybrid males in the Anopheles gambiae complex, we performed crosses between laboratory strains of An. merus and either An. gambiae or An. coluzzii. The reproductive tracts had normal external morphology in hybrid males from crosses between female An. merus and male An. gambiae or An. coluzzii. Despite being sterile, these males could copulate with females for a normal period of time and could transfer a mating plug to induce female oviposition and monogamy. In contrast, the entire reproductive tracts in hybrid males from crosses between female An. gambiae or An. coluzzii and male An. merus were severely underdeveloped. These males had atrophic testes and reduced somatic organs of the reproductive system including male accessary glands and ejaculatory duct. In addition, hybrid males with underdeveloped reproductive tracts displayed a shorter copulation time with females and failed to induce female oviposition and monogamy due to their inability to form and transfer a plug to females during mating. The asymmetry of the phenotypes associated with hybrid male sterility suggests that different genetic factors and molecular mechanisms are responsible for reproductive isolation in reciprocal crosses among species of the An. gambiae complex

A Comprehensive Characterization of the Honeybees in Siberia (Russia)

A comprehensive study of some populations of honeybee (332 colonies) in Siberia (Tomsk region, Krasnoyarsk Krai (Yenisei population), Altai) using morphometric and molecular genetic methods was conducted. Infestation of bees (132 colonies) by Nosema has also been studied. Three variants of the COI-COII mtDNA locus were registered: PQQ, PQQQ (typical for Apis m. mellifera), and Q (specific for southern races). It was established that 64% of bee colonies from the Tomsk region and all colonies studied from the Krasnoyarsk and the Altai territories originate from Apis m. mellifera on the maternal line. According to the morphometric study, the majority of bee colonies of the Tomsk region are hybrids; in some colonies the mismatch of morphometric and mtDNA data was observed. Moreover, the majority of bee colonies infected by Nosema were hybrids. Yenisei population may be considered as a unique Apis m. mellifera population. Microsatellite analysis (loci А008, Ap049, AC117, AC216, Ap243, H110, A024, A113) showed the specific distribution of genotypes and alleles for some loci in the bees, which differ by geographical location. Loci A024 and Ap049 are of considerable interest for further study as candidate markers for differentiation of subspecies; locus A008 can be considered informative for determining of different ecotypes of Apis m. mellifera

The role of chromosome-nuclear envelope attachments in 3D genome organization

Chromosomes are intricately folded and packaged in the cell nucleus and interact with the nuclear envelope. This complex nuclear architecture has a profound effect on how the genome works and how the cells function. The main goal of review is to highlight recent studies on the effect of chromosome–nuclear envelope interactions on chromatin folding and function in the nucleus. The data obtained suggest that chromosome–nuclear envelope attachments are important for the organization of nuclear architecture in various organisms. A combination of experimental cell biology methods with computational modeling offers a unique opportunity to explore the fundamental relationships between different aspects of 3D genome organization in greater details. This powerful interdisciplinary approach could reveal how the organization and function of the genome in the nuclear space is affected by the chromosome–nuclear envelope attachments and will enable the development of novel approaches to regulate gene expression

Микросателлитный маркер mrjp3: определение подвидов медоносной пчелы и/или продуктивности маточного молочка пчелиной семьи

The mrjp3 gene is a member of the mrjp-family that encodes Major Royal Jelly Proteins in bees. In the structure of the mrjp3 gene coding part, a repetitive region, designated as a microsatellite mrjp3 locus, is described. The variability of the mrjp3 micro­satellite locus in 575 honeybees from Siberia (Russia) was studied. In honeybees of different origin (evolutionary branches M and C) inhabited Siberia, the differences in the frequency of allele registration were revealed. The significance of the mrjp3 locus for determining the honeybee subspecies and/or royal jelly productivity of the bee colonies is discussed

Improving the population genetics toolbox for the study of the African malaria vector Anopheles nili: microsatellite mapping to chromosomes

<p>Abstract</p> <p>Background</p> <p><it>Anopheles nili </it>is a major vector of malaria in the humid savannas and forested areas of sub-Saharan Africa. Understanding the population genetic structure and evolutionary dynamics of this species is important for the development of an adequate and targeted malaria control strategy in Africa. Chromosomal inversions and microsatellite markers are commonly used for studying the population structure of malaria mosquitoes. Physical mapping of these markers onto the chromosomes further improves the toolbox, and allows inference on the demographic and evolutionary history of the target species.</p> <p>Results</p> <p>Availability of polytene chromosomes allowed us to develop a map of microsatellite markers and to study polymorphism of chromosomal inversions. Nine microsatellite markers were mapped to unique locations on all five chromosomal arms of <it>An. nili </it>using fluorescent <it>in situ </it>hybridization (FISH). Probes were obtained from 300-483 bp-long inserts of plasmid clones and from 506-559 bp-long fragments amplified with primers designed using the <it>An. nili </it>genome assembly generated on an Illumina platform. Two additional loci were assigned to specific chromosome arms of <it>An. nili </it>based on <it>in silico </it>sequence similarity and chromosome synteny with <it>Anopheles gambiae</it>. Three microsatellites were mapped inside or in the vicinity of the polymorphic chromosomal inversions <it>2Rb </it>and <it>2Rc</it>. A statistically significant departure from Hardy-Weinberg equilibrium, due to a deficit in heterozygotes at the <it>2Rb </it>inversion, and highly significant linkage disequilibrium between the two inversions, were detected in natural <it>An. nili </it>populations collected from Burkina Faso.</p> <p>Conclusions</p> <p>Our study demonstrated that next-generation sequencing can be used to improve FISH for microsatellite mapping in species with no reference genome sequence. Physical mapping of microsatellite markers in <it>An. nili </it>showed that their cytological locations spanned the entire five-arm complement, allowing genome-wide inferences. The knowledge about polymorphic inversions and chromosomal locations of microsatellite markers has been useful for explaining differences in genetic variability across loci and significant differentiation observed among natural populations of <it>An. nili</it>.</p

Genome mapping and characterization of the Anopheles gambiae heterochromatin

<p>Abstract</p> <p>Background</p> <p>Heterochromatin plays an important role in chromosome function and gene regulation. Despite the availability of polytene chromosomes and genome sequence, the heterochromatin of the major malaria vector <it>Anopheles gambiae </it>has not been mapped and characterized.</p> <p>Results</p> <p>To determine the extent of heterochromatin within the <it>An. gambiae </it>genome, genes were physically mapped to the euchromatin-heterochromatin transition zone of polytene chromosomes. The study found that a minimum of 232 genes reside in 16.6 Mb of mapped heterochromatin. Gene ontology analysis revealed that heterochromatin is enriched in genes with DNA-binding and regulatory activities. Immunostaining of the <it>An. gambiae </it>chromosomes with antibodies against <it>Drosophila melanogaster </it>heterochromatin protein 1 (HP1) and the nuclear envelope protein lamin Dm₀identified the major invariable sites of the proteins' localization in all regions of pericentric heterochromatin, diffuse intercalary heterochromatin, and euchromatic region 9C of the 2R arm, but not in the compact intercalary heterochromatin. To better understand the molecular differences among chromatin types, novel Bayesian statistical models were developed to analyze genome features. The study found that heterochromatin and euchromatin differ in gene density and the coverage of retroelements and segmental duplications. The pericentric heterochromatin had the highest coverage of retroelements and tandem repeats, while intercalary heterochromatin was enriched with segmental duplications. We also provide evidence that the diffuse intercalary heterochromatin has a higher coverage of DNA transposable elements, minisatellites, and satellites than does the compact intercalary heterochromatin. The investigation of 42-Mb assembly of unmapped genomic scaffolds showed that it has molecular characteristics similar to cytologically mapped heterochromatin.</p> <p>Conclusions</p> <p>Our results demonstrate that <it>Anopheles </it>polytene chromosomes and whole-genome shotgun assembly render the mapping and characterization of a significant part of heterochromatic scaffolds a possibility. These results reveal the strong association between characteristics of the genome features and morphological types of chromatin. Initial analysis of the <it>An. gambiae </it>heterochromatin provides a framework for its functional characterization and comparative genomic analyses with other organisms.</p

A standard photomap of ovarian nurse cell chromosomes and inversion polymorphism in Anopheles beklemishevi

Background Anopheles beklemishevi is a member of the Maculipennis group of malaria mosquitoes that has the most northern distribution among other members of the group. Although a cytogenetic map for the larval salivary gland chromosomes of this species has been developed, a high-quality standard cytogenetic photomap that enables genomics and population genetics studies of this mosquito at the adult stage is still lacking. Methods In this study, a cytogenetic map for the polytene chromosomes of An. beklemishevi from ovarian nurse cells was developed using high-resolution digital imaging from field collected mosquitoes. PCR-amplified DNA probes for fluorescence in situ hybridization (FISH) were designed based on the genome of An. atroparvus. The DNA probe obtained by microdissection procedures from the breakpoint region was labelled in a DOP-PCR reaction. Population analysis was performed on 371 specimens collected in 18 locations. Results We report the development of a high-quality standard photomap for the polytene chromosomes from ovarian nurse cells of An. beklemishevi. To confirm the suitability of the map for physical mapping, several PCR-amplified probes were mapped to the chromosomes of An. beklemishevi using FISH. In addition, we identified and mapped DNA probes to flanking regions of the breakpoints of two inversions on chromosome X of this species. Inversion polymorphism was determined in 13 geographically distant populations of An. beklemishevi. Four polymorphic inversions were detected. The positions of common chromosomal inversions were indicated on the map. Conclusions The study constructed a standard photomap for ovarian nurse cell chromosomes of An. beklemishevi and tested its suitability for physical genome mapping and population studies. Cytogenetic analysis determined inversion polymorphism in natural populations of An. beklemishevi related to this species’ adaptatio

Mitotic-chromosome-based physical mapping of the Culex quinquefasciatus genome

The genome assembly of southern house mosquito Cx. quinquefasciatus is represented by a high number of supercontigs with no order or orientation on the chromosomes. Although cytogenetic maps for the polytene chromosomes of this mosquito have been developed, their utilization for the genome mapping remains difficult because of the low number of high-quality spreads in chromosome preparations. Therefore, a simple and robust mitotic-chromosome-based approach for the genome mapping of Cx. quinquefasciatus still needs to be developed. In this study, we performed physical mapping of 37 genomic supercontigs using fluorescent in situ hybridization on mitotic chromosomes from imaginal discs of 4th instar larvae. The genetic linkage map nomenclature was adopted for the chromosome numbering based on the direct positioning of 58 markers that were previously genetically mapped. The smallest, largest, and intermediate chromosomes were numbered as 1, 2, and 3, respectively. For idiogram development, we analyzed and described in detail the morphology and proportions of the mitotic chromosomes. Chromosomes were subdivided into 19 divisions and 72 bands of four different intensities. These idiograms were used for mapping the genomic supercontigs/genetic markers. We also determined the presence of length polymorphism in the q arm of sex-determining chromosome 1 in Cx. quinquefasciatus related to the size of ribosomal locus. Our physical mapping and previous genetic linkage mapping resulted in the chromosomal assignment of 13% of the total genome assembly to the chromosome bands. We provided the first detailed description, nomenclature, and idiograms for the mitotic chromosomes of Cx. quinquefasciatus. Further application of the approach developed in this study will help to improve the quality of the southern house mosquito genome

A major genetic locus controlling natural Plasmodium falciparum infection is shared by East and West African Anopheles gambiae

Background: Genetic linkage mapping identified a region of chromosome 2L in the Anopheles gambiae genome that exerts major control over natural infection by Plasmodium falciparum. This 2L Plasmodium-resistance interval was mapped in mosquitoes from a natural population in Mali, West Africa, and controls the numbers of P. falciparum oocysts that develop on the vector midgut. An important question is whether genetic variation with respect to Plasmodium-resistance exists across Africa, and if so whether the same or multiple geographically distinct resistance mechanisms are responsible for the trait. Methods: To identify P falciparum resistance loci in pedigrees generated and infected in Kenya, East Africa, 28 microsatellite loci were typed across the mosquito genome. Genetic linkage mapping was used to detect significant linkage between genotype and numbers of midgut oocysts surviving to 7–8 days post-infection. Results: A major malaria-control locus was identified on chromosome 2L in East African mosquitoes, in the same apparent position originally identified from the West African population. Presence of this resistance locus explains 75% of parasite free mosquitoes. The Kenyan resistance locus is named EA_Pfin1 (East Africa_ Plasmodium falciparum Infection Intensity). Conclusion: Detection of a malaria-control locus at the same chromosomal location in both East and West African mosquitoes indicates that, to the level of genetic resolution of the analysis, the same mechanism of Plasmodium-resistance, or a mechanism controlled by the same genomic region, is found across Africa, and thus probably operates in A. gambiae throughout its entire range