Homologous banding patterns in the polytene chromosomes from the larval salivary glands and ovarian nurse cells of Anopheles stephensi liston (Culicidae)

A comparison of the banding patterns of two homologous polytene chromosome arms from the larval salivary gland and ovarian nurse cell complement of Anopheles stephensi is presented. The homologous chromosomes from the somatic larval salivary glands and germ-line derived ovarian nurse cells have essentially the same band-interband organisation. An analysis of the ³H-uridine labelling patterns of a small chromosome segment from the two tissues indicates that germ-line polytene chromosomes are not radically different from somatic polytene chromosomes in their patterns of gene expression.     

Systemic reorganization of the architechtonics of polytene chromosomes in onto- and phylogenesis of malaria mosquitoes. Structural features regional of chromosomal adhesion to the nuclear membrane

Principles of organization of chromocenter in salivary gland cells and zones of chromosome attachment to nuclear envelope in ovarian nurse cells were determined. It was shown that blocks of centromeric heterochromatin (alfa-heterochromatin) have no direct connection with nuclear envelope. Such connections are ensured by beta-heterochromatin. Homologous chromosome regions were shown to be of different morphology and nature of chromosome-membrane links in different mosquito species. A map of polytene chromosomes of ovarian nurse cells in Anopheles messeae Fall, was established. No differences were found in band quantity of these chromosomes as compared to salivary gland chromosomes.     

Satellite DNA of Anopheles stephensi liston (Diptera: Culicidae)

Four satellite DNAs in the Anopheles stephensi genome have been defined on the basis of their banding properties in Hoechst 33258-CsCl density gradients. Two of these satellites, satellites I and II, are visible on neutral CsCl density gradients as a light density peak forming approximately 15% of total cellular DNA. Hoechst-CsCl density gradient profiles of DNA extracted from polytene tissues indicates that these satellites are underreplicated in larval salivary gland cells and adult female Malpighian tubules and possibly also in ovarian nurse cells. The chromosomal location of satellite I on mitotic and polytene chromosomes has been determined by in situ hybridisation. Sequences complementary to satellite I are present in approximately equal amounts on a heterochromatic arm of the X and Y chromosomes and are also present, in smaller amounts, at the centromere of chromosome 3. A quantitative analysis of the in situ hybridisation experiments indicates that sequences complementary to satellite I at these two sites differ in their replicative behaviour during polytenisation: heterosomal satellite I sequences are under-replicated relative to chromosome 3 sequences in polytene larval salivary gland and ovarian nurse cell nuclei.     

Species-specific localization of DNA from pericentromeric heterochromatin on polytene chromosomes in the salivary gland cells and 3D-nuclear organization nurse cells in Drosophila virilis and Drosophila kanekoi (Diptera: Drosophilidae)

Microdissection of the chromocenter of D. virilis salivary gland polytene chromosomes has been carried out and the region-specific DNA library (DvirIII) has been obtained. FISH was used for DvirIII hybridization with salivary gland polytene chromosomes and ovarian nurse cells of D. virilis and D. kanekoi. Localization of DvirIII in the pericentromeric regions of chromosomes and in the telomeric region of chromosome 5 was observed in both species. Moreover, species specificity in the localization of DNA sequences of DvirIII in some chromosomal regions was detected. In order to study the three-dimensional organization of pericentromeric heterochromatin region of polytene chromosomes of ovarian nurse cells of D. virilis and D. kanekoi, 3S FISH DvirIII was performed with nurse cells of these species. As a result, species specificity in the distribution of DvirIII signals in the nuclear space was revealed. Namely, the signal was detected in the local chromocenter at one pole of the nucleus in D. virilis, while the signal from the telomeric region of chromosome 5 was detected on another pole. At the same time, DvirIII signals in D. kanekoi are localized in two separate areas in the nucleus: the first belongs to the pericentromeric region of chromosome 2 and another to pericentromeric regions of the remaining chromosomes.     

The interrelation of the polytene chromosomes of generative tissues in Drosophila melanogaster]

The principles of three dimensional organization of primary and secondary orders polytene chromosomes in ovarian nurse cells of Drosophila melanogaster were elucidated. Contrary to somatic tissues, no joining of chromosome arms into local chromocentre was discovered. The chromosomes are separated in the nuclear space and are attached to the nuclear envelope by the centromeric (and the XL arm--by the telomeric) sites, the arms of autosomes (especially primary polytene chromosomes) being separated in the area of attachment. Polytenized XR arm of the X chromosomes were discovered. The architecture of chromosomes discovered in ovarian nurse cells is tissue-specific and differs considerably from the organization of polytene chromosomes of somatic tissues.     

Extent of polyteny in the pericentric heterochromatin of polytene chromosomes of pseudonurse cells of otu (ovarian tumor) mutants of Drosophila melanogaster

In the polytene nuclei of germ-line cells (ovarian pseudonurse cells) of Drosophila melanogaster females mutant for otu ¹¹ (ovarian tumor), the pericentric heterochromatin is much more abundant than in somatic salivary gland cells. This is due to the degree of heterochromatin compaction (and consequently the level of underreplication) being lower in the nurse cells than in the salivary gland cells. The lower level of compaction probably results in a very low degree of position effect gene inactivation in the ovarian nurse cells.     

Extent of polyteny in the pericentric heterochromatin of polytene chromosomes of pseudonurse cells of otu (ovarian tumor) mutants of Drosophila melanogaster

In the polytene nuclei of germ-line cells (ovarian pseudonurse cells) of Drosophila melanogaster females mutant for otu ¹¹ (ovarian tumor), the pericentric heterochromatin is much more abundant than in somatic salivary gland cells. This is due to the degree of heterochromatin compaction (and consequently the level of underreplication) being lower in the nurse cells than in the salivary gland cells. The lower level of compaction probably results in a very low degree of position effect gene inactivation in the ovarian nurse cells.     

Organization and differential staining of chromosomes from the endomitotic nucleus of trophocytes Calliphora erythrocephala (Diptera: Calliphoridae)

The structure of primary polytene chromosomes and general architecture of nurse cell nuclei was studied in Calliphora erythrocephala using various methods of differential chromosome banding(G-, R-, C-banding; Ag- and DAPI staining), chromospecific DNA probes and fluorescence in situ hybridization. This analysis revealed differential compaction of particular chromosome regions. The localization of material of polytene chromosome 6 is retained after its rearrangement and the formation of the internal reticular structure of the nucleus. Polytene chromosomes of ovarian nurse cells were shown to have blocks of dense compact material; some of them were more intensely stained by AgNO3. The dynamics of the nucleolus formation was traces at all stages of chromosome polytenization in the C. erythrocephala nurse cells.     

Tissue-Specific Differences in the Spatial Interposition of X-Chromosome and 3R Chromosome Regions in the Malaria Mosquito Anopheles messeae Fall.

Spatial organization of a chromosome in a nucleus is very important in biology but many aspects of it are still generally unresolved. We focused on tissue-specific features of chromosome architecture in closely related malaria mosquitoes, which have essential inter-specific differences in polytene chromosome attachments in nurse cells. We showed that the region responsible for X-chromosome attachment interacts with nuclear lamina stronger in nurse cells, then in salivary glands cells in Anopheles messeae Fall. The inter-tissue differences were demonstrated more convincingly in an experiment of two distinct chromosomes interposition in the nucleus space of cells from four tissues. Microdissected DNA-probes from nurse cells X-chromosome (2BC) and 3R chromosomes (32D) attachment regions were hybridized with intact nuclei of nurse cells, salivary gland cells, follicle epithelium cells and imaginal disсs cells in 3D-FISH experiments. We showed that only salivary gland cells and follicle epithelium cells have no statistical differences in the interposition of 2BC and 32D. Generally, the X-chromosome and 3R chromosome are located closer to each other in cells of the somatic system in comparison with nurse cells on average. The imaginal disсs cell nuclei have an intermediate arrangement of chromosome interposition, similar to other somatic cells and nurse cells. In spite of species-specific chromosome attachments there are no differences in interposition of nurse cells chromosomes in An. messeae and An. atroparvus Thiel. Nurse cells have an unusual chromosome arrangement without a chromocenter, which could be due to the special mission of generative system cells in ontogenesis and evolution.     

A standard photomap of ovarian nurse cell chromosomes in the European malaria vector Anopheles atroparvus

Anopheles atroparvus (Diptera: Culicidae) is one of the main malaria vectors of the Maculipennis group in Europe. Cytogenetic analysis based on salivary gland chromosomes has been used in taxonomic and population genetic studies of mosquitoes from this group. However, a high‐resolution cytogenetic map that could be used in physical genome mapping in An. atroparvus is still lacking. In the present study, a high‐quality photomap of the polytene chromosomes from ovarian nurse cells of An. atroparvus was developed. Using fluorescent in situ hybridization, 10 genes from the five largest genomic supercontigs on the polytene chromosome were localized and 28% of the genome was anchored to the cytogenetic map. The study established chromosome arm homology between An. atroparvus and the major African malaria vector Anopheles gambiae, suggesting a whole‐arm translocation between autosomes of these two species. The standard photomap constructed for ovarian nurse cell chromosomes of An. atroparvus will be useful for routine physical mapping. This map will assist in the development of a fine‐scale chromosome‐based genome assembly for this species and will also facilitate comparative and evolutionary genomics studies in the genus Anopheles.     

Chromosome Organization and Differential Banding in Endomitotic Nuclei of Nurse Cells of Calliphora erythrocephala (Diptera: Calliphoridae)

The structure of primary polytene chromosomes and general architecture of nurse cell nuclei was studied in Calliphora erythrocephala using various methods of differential chromosome banding(G-, R-, C-banding; Ag-, and DAPI staining), chromospecific DNA probes and fluorescence in situ hybridization. This analysis revealed differential compaction of particular chromosome regions. The localization of material of polytene chromosome 6 is retained after its rearrangement and the formation of the internal reticular structure of the nucleus. Polytene chromosomes of ovarian nurse cells were shown to have blocks of dense compact material; some of them were more intensely stained by AgNO₃. The dynamics of the nucleolus formation was traces at all stages of chromosome polytenization in the C. erythrocephala nurse cells.     

DNA replication in polytene chromosomes: Similarity of termination patterns in somatic and germ-line derived polytene chromosomes of Anopheles stephensi liston (Diptera: Culicidae)

DNA replication is initiated in the ovarian follicles of the anautogenous Culicid Anopheles stephensi in response to a blood meal. The chronology of nurse cell polytene chromosome³H-thymidine labelling patterns has been defined and the terminal labelling patterns of the nurse cell and larval salivary gland polytene X-chromosomes have been compared and found to be essentially similar.     

Systemic reorganization of the architectonics of polytene chromosomes in the onto- and phylogenesis of malaria mosquitoes

Cardinal differences in the spatial organization of polytene chromosomes in the nuclei of salivary gland cells (malphigian tubules) and nurse ovarian cells in malarial mosquitoes of Anopheles maculipennis complex are found. The chromosomes have typical chromocentric organization in salivary gland cells and malphigian tubules. In contrast to these cells, the trophocytes have no single chromocentre and some of their chromosomes are rigidly attached to the nucleus envelope with the centromeric parts or with the particular loci. The loci-specificity of the X-chromosome intercalary parts' attachment to the nucleus envelope is found in Anopheles messeae.     

Isolation and partial characterization of replication intermediates in Chironomus polytene chromosomes

DNA replication was investigated in cells with polytene chromosomes. The cells were obtained from the salivary glands of the dipteran Chironomus tentans. Polytene chromosomes are characterized by a specific and constant band — interband structure formed by the lateral association of homologous chromatids side by side. — The salivary gland DNA was labelled by injection of radioactive precursor into the living animal, extracted with a neutral nondenaturing buffer at 25° C and finally characterized by agarose gel electrophoresis. Radioactive DNA pulse-labelled for 30–60 min was released from the polytene chromosomes during cell lysis in the form of double-stranded fragments. The fragments, which show a heterogeneous appearance in gel electrophoresis, are probably produced in the living cell by the joining of several Okazaki fragments. The release of the fragments from the polytene chromosome is prevented by lysis at 0° C instead of 25° C. The size of the double-stranded fragments range between 3.75–6×10⁶ D. Moreover, after a time-lag the fragments are joined together to produce a high-molecular weight DNA. The existence of these nascent DNA fragments is discussed in relation to an earlier proposal that each band in the polytene chromosome may function as a separate replication unit.     

兴义维蚋多线染色体研究（英文）

首次在国内对兴义维蚋Simulium (Wilhelmia) xingyiense的多线染色体进行研究, 并提供其多线染色体标准图。选取兴义维蚋的成熟幼虫, 用改良苯酚品红染色法进行唾腺多线染色体制备, 并进行测量、 描述及分析。结果表明： 兴义维蚋多线染色体数目为3对（2n=6）。Ⅰ号染色体具中央着丝粒, Ⅱ和Ⅲ号染色体均为亚中央着丝粒染色体。核仁组织者区位于Ⅰ号染色体短臂近着丝粒端。巴尔比尼氏环和双泡位于Ⅱ号染色体短臂近中央位置。3对染色体的着丝粒区可形成明显的染色中心。兴义维蚋多线染色体具有多态性的倒位, 倒位频率为0.64。兴义维蚋多线染色体的着丝粒、 核仁组织区、 巴氏环、 双泡等主要特征性结构的位置及形态恒定一致,可作为该种的重要鉴别特征。其多态性的倒位可为该蚋种在细胞水平上进行蚋类分类鉴别和系统发育等研究提供基础资料。     

Polytene chromosome maps of the melon fly Bactrocera cucurbitae (Diptera: Tephritidae).

Standard photographic maps of the polytene chromosomes are presented for the melon fly Bactrocera cucurbitae, a serious pest of fleshy fruits and vegetables. Five larval salivary gland polytene chromosomes (10 polytene arms) were isolated, and their characteristic features and landmarks have been recognized. Banding patterns of each of the polytene arms are presented, where variation in band intensity and puffs appear to reflect fundamental differences in chromosomes. The whole polytene genome has been typically mapped by dividing it into 100 sections and the subsections were lettered. The mitotic chromosomes of larval brain ganglia are also examined, five pairs of autosomes and an XX/XY sex chromosome pair. In addition, a heterochromatic mass corresponding to the sex chromosomes are observed in the polytene nuclei of salivary gland tissue. This investigation showed that B. cucurbitae has excellent cytological material for polytene chromosome analysis and proved to be very useful for obtaining more detailed genetic information on the pest's natural populations.     

Spatial organization of polytene chromosomes in ovarian trophocyte nuclei of the malaria mosquito Anopheles labranchiae Fall.]

Spatial arrangement of polytene chromosomes in the ovarian trophocyte nuclei was studied in Anopheles labranchiae Fall. The system of chromosome attachment to the nuclear envelope in this species was found to differ from those in other species of the A. maculipennis complex. These results confirm that the spatial organization of nurse ovarian cell chromosomes is species-specific.     

Polytene chromosomes from ovarian pseudonurse cells of the Drosophila melanogaster otu mutant

Certain mutant alleles of the otu locus in Drosophila melanogaster produce abnormal nurse cells in the ovaries. These cells are called pseudonurse cells (PNC), since they generate polytene chromosomes instead of endopolyploid ones and do not normally have an oocyte to nurse. The banding pattern of polytene chromosome 3 from the salivary glands (SG) and from PNCs of homozygous otu ¹ females was compared and a detailed photomap of PNC chromosomes with different degrees of polyteny is presented. The banding pattern was found to be strikingly similiar in the two tissues. The puffing pattern of the PNC chromosomes was also studied and the function of the PNC chromosomes is discussed. No constrictions or breaks were found in the PNC chromosomes which seems to indicate that these sites, which are known to be underreplicated in the SG chromosomes, are equally replicated along with the rest of the chromosomes in the PNC nuclei.