Chromosome Banding Patterns Research Articles

Polytene Chromosome Banding Pattern three Drosophila species from Bangladesh

Polytene Chromosome Banding Pattern three Drosophila species from Bangladesh

Genetic relationships of three species of black flies (Diptera: Simuliidae) in Taiwan

As an island about 150 km from the mainland, Taiwan would be expected to have endemic species. About 64 % of its 36 species of black flies are considered endemic, more than twice the level of endemicity that has been recorded for all insects on the island. To begin assessing the validity of the high level of endemism for the Simuliidae, we used giant chromosome banding patterns and cytochrome c oxidase I (COI) sequences, against a well-defined morphological backdrop, to evaluate three of Taiwan's black flies, Simulium chungi Takaoka & Huang, S. pingtungense Huang & Takaoka, and S. sakishimaense Takaoka. Molecular data revealed high similarity of populations of S. sakishimaense in Taiwan and at the type locality on Ishigaki Island, Japan, about 180 km to the east. Thus, populations referred to as S. sakishimaense in Taiwan are conspecific with typical S. sakishimaense in Japan, confirming their non-endemicity in Taiwan. Simulium sakishimaense might have reached Ishigaki by island hopping via Taiwan from the Chinese mainland. Chromosomes and the COI gene agree with morphology that S. sakishimaense is a member of the S. multistriatum species group although the chromosomal banding patterns do not indicate that it is distinct from S. fenestratum Edwards on the mainland. Although molecular sequences indicate S. sakishimaense is monophyletic, this taxon falls within the same Operational Taxonomic Unit as nine other members of the S. multistriatum group, including S. fenestratum. Simulium pingtungense, in agreement with morphology, is molecularly distinct from the 10 other analyzed members of the S. striatum species group, tentatively suggesting that it is endemic to Taiwan, pending analysis of samples from mainland China. Simulium chungi in Taiwan is chromosomally and molecularly unique, with larvae resembling those of S. saskishimaense. It is not, however, a member of either the S. multistriatum or S. striatum species groups. For now, the S. chungi species group remains a legitimate taxon consisting of two species. Strengthening the case for endemic taxa in Taiwan awaits analysis of key samples from the Chinese mainland.

Two Nested Inversions in the X Chromosome Differentiate the Dominant Malaria Vectors in Europe, Anopheles atroparvus and Anopheles messeae.

The Maculipennis subgroup of malaria mosquitoes includes both dominant malaria vectors and non-vectors in Eurasia. Understanding the genetic factors, particularly chromosomal inversions, that differentiate Anopheles species can provide valuable insights for vector control strategies. Although autosomal inversions between the species in this subgroup have been characterized based on the chromosomal banding patterns, the number and positions of rearrangements in the X chromosome remain unclear due to the divergent banding patterns. Here, we identified two large X chromosomal inversions, approximately 13 Mb and 10 Mb in size, using fluorescence in situ hybridization. The inversion breakpoint regions were mapped by hybridizing 53 gene markers with polytene chromosomes of An. messeae. The DNA probes were designed based on gene sequences from the annotated An. atroparvus genome. The two nested inversions resulted in five syntenic blocks. Only two small syntenic blocks, which encompass 181 annotated genes in the An. atroparvus genome, changed their position and orientation in the X chromosome. The analysis of the An. atroparvus genome revealed an enrichment of gene ontology terms associated with immune system and mating behavior in the rearranged syntenic blocks. Additionally, the enrichment of DNA transposons was found in sequences homologous to three of the four breakpoint regions. This study demonstrates the successful application of the physical genome mapping approach to identify rearrangements that differentiate species in insects with polytene chromosomes.

Masked Conditional Variational Autoencoders for Chromosome Straightening.

Karyotyping is of importance for detecting chromosomal aberrations in human disease. However, chromosomes easily appear curved in microscopic images, which prevents cytogeneticists from analyzing chromosome types. To address this issue, we propose a framework for chromosome straightening, which comprises a preliminary processing algorithm and a generative model called masked conditional variational autoencoders (MC-VAE). The processing method utilizes patch rearrangement to address the difficulty in erasing low degrees of curvature, providing reasonable preliminary results for the MC-VAE. The MC-VAE further straightens the results by leveraging chromosome patches conditioned on their curvatures to learn the mapping between banding patterns and conditions. During model training, we apply a masking strategy with a high masking ratio to train the MC-VAE with eliminated redundancy. This yields a non-trivial reconstruction task, allowing the model to effectively preserve chromosome banding patterns and structure details in the reconstructed results. Extensive experiments on three public datasets with two stain styles show that our framework surpasses the performance of state-of-the-art methods in retaining banding patterns and structure details. Compared to using real-world bent chromosomes, the use of high-quality straightened chromosomes generated by our proposed method can improve the performance of various deep learning models for chromosome classification by a large margin. Such a straightening approach has the potential to be combined with other karyotyping systems to assist cytogeneticists in chromosome analysis.

Learning Disentangled Representation for Chromosome Straightening

Chromosome straightening plays an important role in karyotype analysis. Common straightening methods usually adopt geometric algorithms, which tend to affect the chromosome banding patterns in the process of straightening, resulting in feature changes, loss of details, and poor generalization. To solve these problems, this paper proposes a novel straightening method based on disentanglement representation learning. Our method consists of two main components: the Disentanglement Representation Encoder (DRE) and the Straightening Generator (SG), where DRE discovers and disentangles the bent representation and the content representation in the latent space, while SG is used to generate the straightened chromosome images based on the disentangled representations. Leveraging the bent representation and the content representation disentangled by DRE, our method produces the straightened representation by reducing the bent representation while keeping the content representation unchanged, making straightening chromosome without changing its banding patterns possible. Evaluation results on both the Frechet Initiation Distance (FID) and the Downstream Classification Accuracy (DCA) metrics show that our method achieves good performance.

A comparative analysis of the chromosomes of three FARQ species complex members, Ceratitis rosa, C. quilicii, and C. fasciventris F2 (Diptera: Tephritidae).

The Ceratitis FARQ species complex consists of four highly destructive agricultural pests of Africa, namely C. fasciventris, C. anonae, C. rosa, and C. quilicii. The members of the complex are considered very closely related and the species limits among them are rather obscure. Their economic significance and the need for developing biological methods for their control makes species identification within the complex an important issue, which has become clear that can only be addressed by multidisciplinary approaches. Chromosomes, both mitotic and polytene, can provide a useful tool for species characterization and phylogenetic inference among closely related dipteran species. In the current study, we present the mitotic karyotype and the polytene chromosomes of C. rosa and C. quilicii together with in situ hybridization data. We performed a comparative cytogenetic analysis among the above two species and C. fasciventris, the only other cytogenetically studied member of the FARQ complex, by comparing the mitotic complement and the banding pattern of the polytene chromosomes of each species to the others, as well as by studying the polytene chromosomes of hybrids between them. Our analysis revealed no detectable chromosomal rearrangements discriminating the three FARQ members studied, confirming their close phylogenetic relationships.

The Chironomus species studied by Letha Karunakaran in Singapore, with a review of the status of selected South-East Asian Chironomus

In the 1960s Letha Karunakaran studied the chironomid fauna of Singapore but faced a lack of sufficiently detailed descriptions to enable identification of her material with any certainty. She recognized seven species of Chironomus (s.s) but sent me fixed larval material of only four of these which she tentatively identified as C. apicatus Johannsen 1932, C. costatus Johannsen 1932, C. javanus Kieffer 1924, and C. stupidus Johannsen 1932. She sent fixed larvae to me for confirmation of her identifications, but died before I was able to determine accurate identities from morphology alone. With additional comparative material, along with polytene chromosome banding patterns and DNA barcode sequence from the mitochondrial COI gene, the species have been identified as a form of C. flaviplumus (auct, not Tokunaga)(here called C. flaviplumus Type B), C. circumdatus Kieffer 1916, probably C. striatipennis Kieffer 1910, and Kiefferulus barbatitarsis (Kieffer 1911), respectively. The identification of one species as a form of C. flaviplumus required an assessment of the present state of knowledge of this species where the name has been applied to at least five different species. Determination of a valid name for this species is not currently possible. The confusion of species identification is an indication that there are a number of closely related species which constitute a “C. flaviplumus group”.

A new species of black fly, formerly cytoform C of the Simulium angulistylum complex (Diptera: Simuliidae), from a high mountain in northeastern Thailand.

Cytoform C, one of three cytoforms in the Simulium angulistylum Takaoka & Davies complex from a high mountain in northeastern Thailand was morphologically and molecularly investigated. All known life stages (larva, pupa, adult male and female except egg) were morphologically similar to, but distinguishable from S. angulistylum s. str. and S. isanense Takaoka, Srisuka & Saeung in the adults by the relative length of the fore and hind basitarsi and relative length of the tooth to the claw. It is also morphologically distinct from other species of the S. epistum species-group. Here, it is formally described as a new species, S. prayooki. Molecular genetic data based on mitochondrial cytochrome c oxidase subunit I (COI) also supported the morphological similarity between the new species and the two related known species (S. angulistylum s. str. and S. isanense) as phylogenetic analysis retrieved them all from a single clade and with a low level of interspecific genetic divergence (1.74%). This might possibly have resulted from incomplete lineage sorting as they are likely to share a recent common ancestor. Despite limitation of molecular genetic differentiation, the new species was distinctly different from two other cytoforms of S. angulistylum complex based on polytene chromosome banding patterns and ecology of the immature stages. Thus, this study highlights the necessity of using an integrated approach for fully understanding black fly biodiversity.

PB1801: CHROMOSOMAL ABNORMALITIES DURING THE CLINICAL COURSE OF ADULT ACUTE MYELOID LEUKEMIA

Background: Using conventional cytogenetics, an abnormal karyotype can be detected in 60-70% of adult acute myeloid leukemia (AML) patients. Taking into consideration the identified cytogenetic abnormalities AML patients are currently classified into three risk groups: favorable, intermediate and adverse. These genetic abnormalities are the most important factors in determining response to chemotherapy as well as outcome in AML. Aims: Aim of this study was to detect the diagnostic and prognostic significance of chromosomal abnormalities in leukemic cells at different phases of AML. Methods: Cytogenetic investigations of bone marrow and/or peripheral blood cells from 140 adult patients were performed during clinical evolution of AML: in newly diagnosed patients, in remission and at relapse. The methods of conventional cytogenetics (GTG) and fluorescence in situ hybridization (FISH) were used. Cytogenetic methods were performed using standard techniques and karyotypes were described according to the International System for Human Cytogenetic Nomenclature. Results: Cytogenetic investigations of 140 adult AML patients were performed in newly diagnosed patients, in remission and at relapse. Structural (del(5q), del(7q), rearrangements of 3q, 12p, 17p and 11q23, t(8;21)(q22;q22), t(9;22)(q34;q11), t(15;17)(q22;q21), t(16;16)(p13;q22), inv(16)(p13q22), marker and ring chromosomes, acentric structures and others) and numerical (-5, -7, -Y, +8, monosomal karyotype and others) chromosomal abnormalities in leukemic cells were found. Some genetic abnormalities (BCR/ABL1, PML/RARa, AML1/ETO, CBFβ/MYH11 fusion genes) were detected by molecular genetic methods (FISH). Spectrum of cytogenetic abnormalities had an important diagnostic and prognostic significance. Diagnosis of AML was possible due to the presence of specific genetic markers that can confirm some types of AML (AML with t(8;21)(q22;q22), t(9;22)(q34;q11), t(15;17)(q22;q21), t(16;16)(p13;q22)/inv(16)(p13q22), 3q21q26 rearrangements, BCR/ABL1, PML/RARa, AML1/ETO, CBFβ/MYH11 fusion genes). Taking into consideration the identified cytogenetic abnormalities AML patients were classified by risk groups: the group of patients with adverse cytogenetic markers (3q21q26 rearrangements, -5, -7, t(9;22)(q34;q11), BCR/ABL1 fusion gene, multiple changes (≥3), monosomal karyotype), the intermediate risk group without significant prognostic markers and the group with favorable prognostic factors (t(8;21)(q22;q22), t(15;17)(q22;q21), t(16;16)(p13;q22)/inv(16)(p13q22), AML1/ETO, PML/RARa, CBFβ/MYH11 fusion genes). In remission cytogenetic investigations showed a normal karyotype without cytogenetically visible changes in all patients. Cytogenetic investigations at relapse were performed in 5 of 140 AML cases. Additional/secondary chromosomal aberrations in leukemic cells or new cells clones with multiple structural and numerical changes at relapse was not detected. Summary/Conclusion: Cytogenetic investigations had an important significance for diagnosis, prognosis and selection the optimal treatment strategy of AML. Besides the analysis of chromosome banding patterns it is necessary for patients with AML to apply molecular genetic studies, namely FISH and polymerase chain reaction (PCR). Taking into consideration the identified cytogenetic abnormalities AML patients were classified by risk groups. Presence of the additional/secondary chromosomal aberrations in leukemic cells or new cells clones with multiple structural and numerical changes at AML relapse is the one sign of clonal evolution and progression of disease.

Chromosome Evolution in the Family Solanaceae.

This review summarizes and discusses the knowledge of cytogenetics in Solanaceae, the tomato family, its current applications, and prospects for making progress in fundamental systematic botany and plant evolution. We compile information on basic chromosome features (number, size, morphology) and molecular cytogenetics (chromosome banding and rDNA patterns). These data were mapped onto the Solanaceae family tree to better visualize the changes in chromosome features and evaluate them in a phylogenetic context. We conclude that chromosomal features are important in understanding the evolution of the family, especially in delimiting clades, and therefore it is necessary to continue producing this type of data. The potential for future applications in plant biology is outlined. Finally, we provide insights into understanding the mechanisms underlying Solanaceae’s diversification that could substantially contribute to developing new approaches for future research.

Chromosomal and Molecular Diversity in the Simulium ornatum Group (Diptera: Simuliidae) in the Western Tian Shan Range of Central Asia.

Simple SummaryMembers of the Simulium ornatum group are among the most abundant and widely distributed black flies in the Palearctic region. We investigated the chromosomal, molecular, and morphological diversity of this group across the varied landscape of Kyrgyzstan. Morphology and chromosomal band patterns suggested the presence of one or two species, whereas mitochondrial DNA sequences indicated up to three species. We linked the name Simulium mesasiaticum with cytologically undifferentiated sex chromosomes, one of three mitochondrial DNA clusters, and higher elevations. We tentatively associated the name Simulium ferganicum with differentiated sex chromosomes, a second DNA cluster, and lower elevations. One Kyrgyz larva in a third DNA cluster could not be linked to a formal species name. The analyses also indicated that Simulium ornatum, the namesake of the entire group, does not occur in Kyrgyzstan despite previous records. The results demonstrate that using only one source of data does not provide a complete picture of the biodiversity and integrated taxonomy is often necessary for species resolution in the family Simuliidae.By any measure, such as abundance, species diversity or geographic range, the Simulium ornatum species group is one of the most successful Palearctic taxa of black flies. To explore potential diversity in this group in the Tian Shan range of Central Asia, we focused on Kyrgyzstan, in which three nominal morphospecies have been recorded. Among our samples, we morphologically identified S. mesasiaticum Rubtsov and a second possible species tentatively identified as S. ferganicum Rubtsov. By analyzing banding patterns of the larval polytene chromosomes, we discovered two fixed inversions, two sex-linked rearrangements, and 19 autosomal rearrangements, including supernumerary B chromosomes. The chromosomal data indicate minimal diversity of only one or two species across the surveyed area of nearly 50,000 km2. Mitochondrial DNA (CO1) sequences fell into three distinct clusters, possibly representing separate species. The chromosomal, molecular, and morphological data indicate that Kyrgyz populations are unique within the S. ornatum group, but the data sets are not entirely congruent. Thus, reconciling data sets and assigning existing names is tentative. Simulium mesasiaticum is linked with undifferentiated sex chromosomes, one of the three CO1 clades, and higher elevations, whereas S. ferganicum is tenuously associated with differentiated sex chromosomes, a separate CO1 clade, and lower elevations. These associations leave one Kyrgyz larva, which is in a third CO1 clade, unlinked to a formal species name. Our analyses also indicate that S. ornatum Meigen sensu stricto, contrary to previous reports, does not occur in Kyrgyzstan and should be deleted from the country’s faunal list.

Comparative cytogenetics in three species of Wood-Warblers (Aves: Passeriformes: Parulidae) reveal divergent banding patterns and chromatic heterogeneity for the W chromosome

Chromosomal rearrangements are an important process in the evolution of species. It is assumed that these rearrangements occur near repetitive sequences and heterochromatic regions. Avian karyotypes have diverse chromosomal band patterns and have been used as the parameters for phylogenetic studies. Although the group has a high diversity of species, no more than 12% has been analyzed cytogenetically, and the Parulidae family are extremely underrepresented in these studies. The aim of this study was to detect independent or simultaneous chromosomal rearrangements, and also to analyze chromosomal banding convergences and divergences of three Wood-Warblers species (Myiothlypis leucoblephara, Basileuterus culicivorus, and Setophaga pitiayumi). Our CBG-band results reveal an unusual W sex chromosome in the three studied species, containing a telomeric euchromatic region. The GTG and RBG bands identify specific regions in the macrochromosomes involved in the rearrangements. Cytogenetic data confirm the identification of speciation processes at the karyotypic of this group.

Identification of the Sibling Species of the Blackfly, Simulium damnosum Complex Using their Polytene Chromosomal Banding Patterns in Oji River System, Enugu State, Nigeria

Identification of the sibling species of the blackfly, S. damnosum complex using their polytene chromosomal banding patterns in Oji river system was carried out with the aim of accurately identifying the particular sibling species of S. damnosum complex involved in the transmission of onchocerciasis in Oji-river LGA and environ. Simulium damnosum complex larvae were collected monthly in forty eight (48) breeding sites in four sampling units for three years in the Oji river system in wet and dry seasons. Collected larvae were preserved in cold Carnoy’s solution prior to processing. Salivary gland chromosomes were extracted, processed and analyzed microscopically for polytene chromosomal banding patterns. Three sibling species of Simulium damnosum complex that breed in the Oji river system were identified in varying degrees. They included S. squamosum, S. yahense and S. damnosum sensu stricto (s.s.). Variation in the occurrence of the sibling species was statistically significant. Dry and wet season catches for all the sibling species in the sampling units were found to differ statistically. The identified sibling species of S. damnosum complex are known to be vectors of Onchocerca volvulus, the causative agent of onchocerciasis, a disease highly prevalent in Oji-river LGA and environ.

Incipient speciation in Calceolaria polyrhiza complex (Calceolariaceae): cytogenetic analysis supports molecular and morphological data

ABSTRACT Calceolaria polyrhiza is a perennial herb distributed in southern South America. The species is highly polymorphic and includes four described morphotypes that were previously considered different species. We performed a detailed study of the karyotype of each morphotype considering at least two localities for each one, with the aim of contributing to the taxonomic delimitation of the Calceolaria polyrhiza complex. In addition, a principal component analysis and a mapping of chromosome traits onto a phylogeny of nuclear DNA sequences were performed. This detailed karyotypic study has revealed specific markers, which have allowed to characterize each morphotype. ‘Prichardii’ morphotype was consistently polyploid. ‘Mendocina’ and ‘Lanceolata’ morphotypes had the highest total heterochromatin amount, with two pairs of chromosomes carrying NORs. ‘Mendocina’ samples showed the most asymmetrical karyotypes. ‘Polyrhiza’ morphotype had the most symmetrical karyotypes of the four morphotypes and the simplest fluorescent chromosome banding pattern. Thus, the four morphotypes could be characterized by chromosomal data and, together with the phylogenetic analysis of molecular data, could be considered taxonomic units in the process of diversification.

An analysis on the divergence of Chironomid spp. based on the study of 18S rRNA and polytene chromosome organization in the species revealing the role of environment on speciation

BackgroundNine species of Chironomus evolved throughout the world were measured for their divergence with regard to their DNA sequences concerning 18S rRNA since it is conserved for a specific species. With the advancement of the field of molecular evolution, cytogenetics requires further correlation between molecular architecture and morphological features of a species to compare amongst others to decipher their role in speciation. Therefore, divergence of DNA sequences of the Chironomus were compared with differences in the polytene chromosome features of most of the species under this investigation to evaluate underlying correlation among them, if any, to finally establish a novel method of molecular classification broadly applicable in cytogenetics studies.ResultsWhen Chironomus javanus Kieffer was considered as a reference organism, an in silico pair-wise alignment of sequences for the 18S rRNA gene regions of the other eight different species of the same genus exhibited nucleotide sequence homology ranging from 67 to 98%. This divergence of the species under consideration might be due to environmental impact causing alteration of nitrogenous bases probably due to mismatch pairing in DNA replication. This may be suggested as a cause of evolution of species in nature. A concomitant study on the polytene chromosome band patterns of majority of these species belonging to this series also indicated a divergence ranging from 10% to 30%.ConclusionsSequence analysis based on 18S rRNA of nine species of Chironomus under this investigation shows a similarity in the polytene chromosome organization in most of the Chironomid species of the series. Hence, molecular divergence in the species is consistent with cytological difference among Chironomid species. Therefore, molecular data based on 18S rRNA and cytological characters based on the polytene chromosome features of the Chironomid species may be useful for their taxonomical recognition. Moreover, variations concerning two aspects of this study may be correlated to their environmental distinctions.

Dietary Methionine Deficiency Enhances Genetic Instability in Murine Immune Cells.

Both cell and animal studies have shown that complete or partial deficiency of methionine inhibits tumor growth. Consequently, the potential implementation of this nutritional intervention has recently been of great interest for the treatment of cancer patients. Unfortunately, diet alteration can also affect healthy immune cells such as monocytes/macrophages and their precursor cells in bone marrow. As around half of cancer patients are treated with radiotherapy, the potential deleterious effect of dietary methionine deficiency on immune cells prior to and/or following irradiation needs to be evaluated. Therefore, we examined whether modulation of methionine content alters genetic stability in the murine RAW 264.7 monocyte/macrophage cell line in vitro by chromosomal analysis after 1-month culture in a methionine-deficient or supplemented medium. We also analyzed chromosomal aberrations in the bone marrow cells of CBA/J mice fed with methionine-deficient or supplemented diet for 2 months. While all RAW 264.7 cells revealed a complex translocation involving three chromosomes, three different clones based on the banding pattern of chromosome 9 were identified. Methionine deficiency altered the ratio of the three clones and increased chromosomal aberrations and DNA damage in RAW 264.7. Methionine deficiency also increased radiation-induced chromosomal aberration and DNA damage in RAW 264.7 cells. Furthermore, mice maintained on a methionine-deficient diet showed more chromosomal aberrations in bone marrow cells than those given methionine-adequate or supplemented diets. These findings suggest that caution is warranted for clinical implementation of methionine-deficient diet concurrent with conventional cancer therapy.

A Study of Constitutive Heterochromatin and NOR Banding in Three Species of Puntius from the State of Haryana, India

The purpose of the present study was to investigate and compare the karyotypes of three species of Puntius viz. Puntius sarana (Hamilton, 1822), Puntius sophore (Hamilton, 1822) and Puntius ticto (Hamilton, 1822) belonging to family Cyprinidae in terms of chromosomal architecture, banding pattern and number of chromosomes from aquatic ecosystems of Haryana, India. Diploid chromosome no. 50 was observed in all 3 species of Puntius. The chromosomes of 3 species of Puntius showed constitutive heterochromatin at telomeric and centromeric regions of chromosomes.The Ag-NOR (Argyrophilic-Nucleolus Organizer Region) bands were observed on homologous chromosome pair nos. 2, 8 and 14 in P. sophore, pair nos. 2, 9 and 14 in P. ticto. The diploid chromosome number in P. sarana was found to be 2n = 50, 2 pairs of metacentric chromosomes, 3 pairs of subtelocentric and 20 pairs of acrocentric chromosomes. Chromosomal studies on the P. sophore revealed the diploid chromosome number to be 2n = 50, showed 16 pairs of metacentric chromosomes, 5 pairs of submetacentric, 2 pairs of subtelocentric and 2 pairs of acrocentric chromosomes. The diploid chromosome number in P. ticto was found to be 2n = 50, with 15 pairs of metacentric chromosomes, 6 pairs of submetacentric, 2 pairs of subtelocentric and 2 pairs of acrocentric chromosomes. No heteromorphic sex chromosomes were cytologically detected. Variations in chromosomes are observed with respect to earlier studies which may be due to variation in habitat conditions as a result of anthropogenic activities.

CHROMOSOMAL ANALYSIS OF PEROMYSCUS GRATUS (CRICETIDAE) OF TECAMACHALCO, PUEBLA, MEXICO

<p>The description was made of the karyotype of <em>Peromyscus gratus</em> (Cricetidae) in the municipality of Tecamachalco, Puebla. Performing the technique of bone marrow extraction, in the obtention of chromosome, G bands was used Trypsin and for C bands a Barium Hydroxide solution was employed. <em>P</em>. <em>gratus</em> presents a diploid number of 2n = 48 and a fundamental number of NF = 54, the autosomes correspond to one metacentric, one submetacentric, two subtelocentric and 19 pairs telocentric from large to small. The sex chromosome X was subtelocentric and the Y was submetacentric unlike other populations of the species. The chromosomal banding pattern G was obtained. As for chromosome C banding, it was found that the constitutive heterochromatin was in the centromeric regions of the chromosomes.</p>

Linked-read sequencing identifies abundant microinversions and introgression in the arboviral vector Aedes aegypti

BackgroundAedes aegypti is the principal mosquito vector of Zika, dengue, and yellow fever viruses. Two subspecies of Ae. aegypti exhibit phenotypic divergence with regard to habitat, host preference, and vectorial capacity. Chromosomal inversions have been shown to play a major role in adaptation and speciation in dipteran insects and would be of great utility for studies of Ae. aegypti. However, the large and highly repetitive genome of Ae. aegypti makes it difficult to detect inversions with paired-end short-read sequencing data, and polytene chromosome analysis does not provide sufficient resolution to detect chromosome banding patterns indicative of inversions.ResultsTo characterize chromosomal diversity in this species, we have carried out deep Illumina sequencing of linked-read (10X Genomics) libraries in order to discover inversion loci as well as SNPs. We analyzed individuals from colonies representing the geographic limits of each subspecies, one contact zone between subspecies, and a closely related sister species. Despite genome-wide SNP divergence and abundant microinversions, we do not find any inversions occurring as fixed differences between subspecies. Many microinversions are found in regions that have introgressed and have captured genes that could impact behavior, such as a cluster of odorant-binding proteins that may play a role in host feeding preference.ConclusionsOur study shows that inversions are abundant and widely shared among subspecies of Aedes aegypti and that introgression has occurred in regions of secondary contact. This library of 32 novel chromosomal inversions demonstrates the capacity for linked-read sequencing to identify previously intractable genomic rearrangements and provides a foundation for future population genetics studies in this species.

Chromosome Arm Locations of Barley Sucrose Transporter Gene in Transgenic Winter Wheat Lines.

Three transgenic HOSUT lines of winter wheat, HOSUT12, HOSUT20, and HOSUT24, each harbor a single copy of the cDNA for the barley sucrose transporter gene HvSUT1 (SUT), which was fused to the barley endosperm-specific Hordein B1 promoter (HO; the HOSUT transgene). Previously, flow cytometry combined with PCR analysis demonstrated that the HOSUT transgene had been integrated into different wheat chromosomes: 7A, 5D, and 4A in HOSUT12, HOSUT20, and HOSUT24, respectively. In order to confirm the chromosomal location of the HOSUT transgene by a cytological approach using wheat aneuploid stocks, we crossed corresponding nullisomic-tetrasomic lines with the three HOSUT lines, namely nullisomic 7A-tetrasomic 7B with HOSUT12, nullisomic 5D-tetrasomic 5B with HOSUT20, and nullisomic 4A-tetrasomic 4B with HOSUT24. We examined the resulting chromosomal constitutions and the presence of the HOSUT transgene in the F2 progeny by means of chromosome banding and PCR. The chromosome banding patterns of the critical chromosomes in the original HOSUT lines showed no difference from those of the corresponding wild type chromosomes. The presence or absence of the critical chromosomes completely corresponded to the presence or absence of the HOSUT transgene in the F2 plants. Investigating telocentric chromosomes occurred in the F2 progeny, which were derived from the respective critical HOSUT chromosomes, we found that the HOSUT transgene was individually integrated on the long arms of chromosomes 4A, 7A, and 5D in the three HOSUT lines. Thus, in this study we verified the chromosomal locations of the transgene, which had previously been determined by flow cytometry, and moreover revealed the chromosome-arm locations of the HOSUT transgene in the HOSUT lines.