The role of rDNA genes in X chromosome association in the aphid Acyrthosiphon pisum

Genome ◽  
1999 ◽  
Vol 42 (3) ◽  
pp. 381-386 ◽  
Author(s):  
Mauro Mandrioli ◽  
Davide Bizzaro ◽  
Monica Giusti ◽  
Gian Carlo Manicardi ◽  
Umberto Bianchi
Keyword(s):  
Silver Staining ◽  
Acyrthosiphon Pisum ◽  
Sex Chromosome ◽  
Promoter Sequence ◽  
Aphid Species ◽  
Chromosome Association ◽  
X Chromosomes ◽  
Rdna Genes ◽  
Nucleolar Material

Silver staining of mitotic metaphases of the aphid A. pisum reveals the presence of argentophilic bridges connecting the two X chromosomes. The presence of nucleolar material connecting sex chromosomes seems to be quite a common phenomenon in organisms belonging to very different phyla, and suggests a role of nucleolar proteins in chromosome association and disjunction. In somatic cells of A. pisum, bridges connecting X chromosomes are detectable not only after silver staining but also after CMA3 staining. This finding suggests that GC rich DNA is involved in this type of association. Molecular analysis of rDNA intergenic spacers shows several 247 bp repeats containing short sequences having a high level of homology with the chi sequence of Escherichia coli and with the consensus core region of human hypervariable minisatellites. Moreover, each 247 bp repeat presents a perfect copy of a promoter sequence for polymerase I. These aphid repeats show structural homologies with a 240 bp repeat, which is considered to be responsible for sex chromosome pairing in Drosophila, not only in view of their common presence within rDNA spacers but also for their length and structure. The presence of chi sequences in the IGS of A. pisum, by promoting unequal crossing-over between rDNA genes, could thus give rise to the nucleolar organizing region (NOR) heteromorphism described in different aphid species. Although X pairing at NORs is fundamental in aphid male determination, the presence of heteromorphism of rDNA genes does not inhibit male determination in the A. pisum clone utilized for our experiments.Key words: aphid, rDNA, sex chromosome association, hotspot, NOR heteromorphism.

The role of rDNA genes in X chromosome association in the aphid Acyrthosiphon pisum

Genome ◽  
1999 ◽  
Vol 42 (3) ◽  
pp. 381-386 ◽  
Author(s):  
Mauro Mandrioli ◽  
Davide Bizzaro ◽  
Monica Giusti ◽  
Gian Carlo Manicardi ◽  
Umberto Bianchi
Keyword(s):  
X Chromosome ◽  
Acyrthosiphon Pisum ◽  
Chromosome Association ◽  
Rdna Genes

THE ROLE OF GENETICS AND OTHER PRENATAL FACTORS IN DISORDERS OF CHILDHOOD

PEDIATRICS ◽  
1956 ◽  
Vol 18 (2) ◽  
pp. 314-317
Author(s):  
Josef Warkany ◽  
F. C. Fraser
Keyword(s):  
Sex Chromosomes ◽  
Gene Pair ◽  
Sex Chromosome ◽  
Rare Event ◽  
Round Table ◽  
X Chromosomes ◽  
Prenatal Factors ◽  
Biochemical Factor ◽  
Hereditary Factors

THE PHYSICIAN interested in the etiology of a disease should always try to ascertain as many etiologic factors as possible, because the causal pathogenic web can often be disturbed from different angles. Although hereditary factors will be the main topic of this round table, we shall stress that they never act in a vacuum. The genes direct the development of the embryo and fetus, but the development depends also upon an environment limited by the mother's body and surroundings. Certain terms are fundamental to an understanding of heredity: Chromosomes. The nuclear carriers of the hereditary factors, the genes. Each nucleated somatic cell of a person's body has 24 pairs of chromosomes, each pair carrying hundreds of genes. One member of each pair is derived from the person's mother and one from the father. In the female there are 23 pairs of autosomes (non-sex chromosomes) and 1 pair of like sex chromosomes (X-chromosomes). In the male there are 23 pairs of autosomes and 1 pair of unlike sex chromosomes (one X and one Y-chromosome). Gene. The particulate biochemical factor responsible for a particular hereditary characteristic. As the genes are carried on the chromosomes, they also occur in pairs. Each pair occupies a particular locus on the chromosomes. Genes located at the same locus are termed alleles. A child gets 1 member of each gene pair from each parent. Sometimes by the rare event of mutation, a gene becomes changed into one that may function abnormally—a "pathologic" gene. Homozygote. An individual in whom the gene pair in question consists of 2 like genes. Heterozygote. An individual in whom the gene pair in question consists of unlike genes. Depending upon the type (dominant or recessive) and location (autosome or sex chromosome) of the gene, several types of inheritance patterns are possible.

Host recognition and acceptance behaviour in two aphid parasitoid species: Aphidius ervi and Aphidius microlophii (Hymenoptera: Braconidae)

1994 ◽  
Vol 84 (1) ◽  
pp. 57-64 ◽  
Author(s):  
F. Pennacchio ◽  
M.C. Digilio ◽  
E. Tremblay ◽  
A. Tranfaglia
Keyword(s):  
Acyrthosiphon Pisum ◽  
Selection Process ◽  
Host Choice ◽  
Aphid Species ◽  
Host Recognition ◽  
Aphidius Ervi ◽  
Aphid Parasitoid ◽  
Host Aphid ◽  
Close Range

AbstractThe host preference and acceptance behaviour of populations of Aphidius ervi Haliday and A. microlophii Pennacchio & Tremblay from southern Italy was investigated. In no host-choice conditions, A. ervi females showed significantly higher attack and oviposition rates on the natural host Acyrthosiphon pisum (Harris) than on the non-host aphid Microlophium carnosum (Buckton)(Homoptera: Aphididae). In contrast, A. microlophii, which specifically parasitizes M. carnosum in the field, attacked both aphid species. However, dissections showed that oviposition of A. microlophii occurred only in a few of the attacked Acyrthosiphon pisum and was significantly less frequent than in M. carnosum. These results were confirmed in experimental host-choice conditions, suggesting that Aphidius microlophii oviposition is possibly regulated by a host haemolymphatic kairomone. Hybrids obtained by crossing A. ervi females with A. microlophii males attacked and oviposited in both aphid species, suggesting that these behavioural events have a strong genetic basis. The oviposition into host or non-host aphids did not elicit an immune defence reaction. The presence of the host's food-plant had no evident close-range effects on parasitoid attack and oviposition in non-host aphids. Aphidius microlophii reared on the non-host aphid Acyrthosiphon pisum produced a significant higher number of mummies after a few generations, suggesting a possible role of larval and early adult conditioning in the host selection process. These results, together with those from previous studies, suggest that Aphidius ervi is best considered as a complex of differentiated populations, characterized by a varying degree of genetic divergence.

scholarly journals Bisection of the X chromosome disrupts the initiation of chromosome silencing during meiosis in Caenorhabditis elegans

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yisrael Rappaport ◽  
Hanna Achache ◽  
Roni Falk ◽  
Omer Murik ◽  
Oren Ram ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Rna Polymerase Ii ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Transcription Analysis ◽  
X Chromosomes ◽  
Unique Character ◽  
Active Transcription ◽  
Heterogametic Sex

AbstractDuring meiosis, gene expression is silenced in aberrantly unsynapsed chromatin and in heterogametic sex chromosomes. Initiation of sex chromosome silencing is disrupted in meiocytes with sex chromosome-autosome translocations. To determine whether this is due to aberrant synapsis or loss of continuity of sex chromosomes, we engineered Caenorhabditis elegans nematodes with non-translocated, bisected X chromosomes. In early meiocytes of mutant males and hermaphrodites, X segments are enriched with euchromatin assembly markers and active RNA polymerase II staining, indicating active transcription. Analysis of RNA-seq data showed that genes from the X chromosome are upregulated in gonads of mutant worms. Contrary to previous models, which predicted that any unsynapsed chromatin is silenced during meiosis, our data indicate that unsynapsed X segments are transcribed. Therefore, our results suggest that sex chromosome chromatin has a unique character that facilitates its meiotic expression when its continuity is lost, regardless of whether or not it is synapsed.

scholarly journals Functional response of Harmonia axyridis preying on Acyrthosiphon pisum nymphs: the effect of temperature

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yasir Islam ◽  
Farhan Mahmood Shah ◽  
Xu Rubing ◽  
Muhammad Razaq ◽  
Miao Yabo ◽  
...  
Keyword(s):  
Functional Response ◽  
High Performance ◽  
Acyrthosiphon Pisum ◽  
Harmonia Axyridis ◽  
Effect Of Temperature ◽  
Functional Responses ◽  
Aphid Control ◽  
Host Aphid ◽  
Predator Foraging

AbstractIn the current study, we investigated the functional response of Harmonia axyridis adults and larvae foraging on Acyrthosiphon pisum nymphs at temperatures between 15 and 35 °C. Logistic regression and Roger’s random predator models were employed to determine the type and parameters of the functional response. Harmonia axyridis larvae and adults exhibited Type II functional responses to A. pisum, and warming increased both the predation activity and host aphid control mortality. Female and 4th instar H. axyridis consumed the most aphids. For fourth instar larvae and female H. axyridis adults, the successful attack rates were 0.23 ± 0.014 h−1 and 0.25 ± 0.015 h−1; the handling times were 0.13 ± 0.005 h and 0.16 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and female H. axyridis and the role of temperature in their efficiency. Further, we discussed such temperature-driven shifts in predation and prey mortality concerning prey-predator foraging interactions towards biological control.

scholarly journals Chromosomal Analysis in Crotophaga ani (Aves, Cuculiformes) Reveals Extensive Genomic Reorganization and an Unusual Z-Autosome Robertsonian Translocation

Cells ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 4
Author(s):  
Rafael Kretschmer ◽  
Ricardo José Gunski ◽  
Analía del Valle Garnero ◽  
Thales Renato Ochotorena de Freitas ◽  
Gustavo Akira Toma ◽  
...  
Keyword(s):  
Robertsonian Translocation ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Rare Event ◽  
Chromosome Morphology ◽  
Z Chromosome ◽  
Molecular Cytogenetic ◽  
Intrachromosomal Rearrangements ◽  
Genomic Reorganization

Although cytogenetics studies in cuckoos (Aves, Cuculiformes) have demonstrated an interesting karyotype variation, such as variations in the chromosome morphology and diploid number, their chromosome organization and evolution, and relation with other birds are poorly understood. Hence, we combined conventional and molecular cytogenetic approaches to investigate chromosome homologies between chicken and the smooth-billed ani (Crotophaga ani). Our results demonstrate extensive chromosome reorganization in C. ani, with interchromosomal rearrangements involving macro and microchromosomes. Intrachromosomal rearrangements were observed in some macrochromosomes, including the Z chromosome. The most evolutionary notable finding was a Robertsonian translocation between the microchromosome 17 and the Z chromosome, a rare event in birds. Additionally, the simple short repeats (SSRs) tested here were preferentially accumulated in the microchromosomes and in the Z and W chromosomes, showing no relationship with the constitutive heterochromatin regions, except in the W chromosome. Taken together, our results suggest that the avian sex chromosome is more complex than previously postulated and revealed the role of microchromosomes in the avian sex chromosome evolution, especially cuckoos.

Male Sterility and Meiotic Drive Associated With Sex Chromosome Rearrangements in Drosophila: Role of X-Y Pairing

Genetics ◽  
1998 ◽  
Vol 149 (1) ◽  
pp. 143-155 ◽  
Author(s):  
Bruce D McKee ◽  
Kathy Wilhelm ◽  
Cynthia Merrill ◽  
Xiao-jia Ren
Keyword(s):  
Male Sterility ◽  
Sex Chromosome ◽  
Meiotic Drive ◽  
Repeated Sequence ◽  
Meiotic Pairing ◽  
Intergenic Spacers ◽  
Male Specific ◽  
The Relationship ◽  
Novel Model

Abstract In Drosophila melanogaster, deletions of the pericentromeric X heterochromatin cause X-Y nondisjunction, reduced male fertility and distorted sperm recovery ratios (meiotic drive) in combination with a normal Y chromosome and interact with Y-autosome translocations (T(Y;A)) to cause complete male sterility. The pericentromeric heterochromatin has been shown to contain the male-specific X-Y meiotic pairing sites, which consist mostly of a 240-bp repeated sequence in the intergenic spacers (IGS) of the rDNA repeats. The experiments in this paper address the relationship between X-Y pairing failure and the meiotic drive and sterility effects of Xh deletions. X-linked insertions either of complete rDNA repeats or of rDNA fragments that contain the IGS were found to suppress X-Y nondisjunction and meiotic drive in Xh−/Y males, and to restore fertility to Xh−/T(Y;A) males for eight of nine tested Y-autosome translocations. rDNA fragments devoid of IGS repeats proved incapable of suppressing either meiotic drive or chromosomal sterility. These results indicate that the various spermatogenic disruptions associated with X heterochromatic deletions are all consequences of X-Y pairing failure. We interpret these findings in terms of a novel model in which misalignment of chromosomes triggers a checkpoint that acts by disabling the spermatids that derive from affected spermatocytes.

scholarly journals Absence of X-chromosome dosage compensation in the primordial germ cells of Drosophila embryos

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryoma Ota ◽  
Makoto Hayashi ◽  
Shumpei Morita ◽  
Hiroki Miura ◽  
Satoru Kobayashi
Keyword(s):  
X Chromosome ◽  
Germ Cells ◽  
Dosage Compensation ◽  
Sex Chromosome ◽  
Primordial Germ Cells ◽  
Histone H4 ◽  
X Chromosomes ◽  
Essential Components ◽  
Msl Complex ◽  
Male Specific

AbstractDosage compensation is a mechanism that equalizes sex chromosome gene expression between the sexes. In Drosophila, individuals with two X chromosomes (XX) become female, whereas males have one X chromosome (XY). In males, dosage compensation of the X chromosome in the soma is achieved by five proteins and two non-coding RNAs, which assemble into the male-specific lethal (MSL) complex to upregulate X-linked genes twofold. By contrast, it remains unclear whether dosage compensation occurs in the germline. To address this issue, we performed transcriptome analysis of male and female primordial germ cells (PGCs). We found that the expression levels of X-linked genes were approximately twofold higher in female PGCs than in male PGCs. Acetylation of lysine residue 16 on histone H4 (H4K16ac), which is catalyzed by the MSL complex, was undetectable in these cells. In male PGCs, hyperactivation of X-linked genes and H4K16ac were induced by overexpression of the essential components of the MSL complex, which were expressed at very low levels in PGCs. Together, these findings indicate that failure of MSL complex formation results in the absence of X-chromosome dosage compensation in male PGCs.

scholarly journals Role of Kaposi's Sarcoma-Associated Herpesvirus C-Terminal LANA Chromosome Binding in Episome Persistence

2009 ◽  
Vol 83 (9) ◽  
pp. 4326-4337 ◽  
Author(s):  
Brenna Kelley-Clarke ◽  
Erika De Leon-Vazquez ◽  
Katherine Slain ◽  
Andrew J. Barbera ◽  
Kenneth M. Kaye
Keyword(s):  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Chromosome Association ◽  
Mitotic Chromosomes ◽  
Dividing Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Self Association ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Chromosome Binding

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) LANA is an 1,162-amino-acid protein that tethers terminal repeat (TR) DNA to mitotic chromosomes to mediate episome persistence in dividing cells. C-terminal LANA self-associates to bind TR DNA. LANA contains independent N- and C-terminal chromosome binding regions. N-terminal LANA binds histones H2A/H2B to attach to chromosomes, and this binding is essential for episome persistence. We now investigate the role of C-terminal chromosome binding in LANA function. Alanine substitutions for LANA residues 1068LKK1070 and 1125SHP1127 severely impaired chromosome binding but did not reduce the other C-terminal LANA functions of self-association or DNA binding. The 1068LKK1070 and 1125SHP1127 substitutions did not reduce LANA's inhibition of RB1-induced growth arrest, transactivation of the CDK2 promoter, or C-terminal LANA's inhibition of p53 activation of the BAX promoter. When N-terminal LANA was wild type, the 1068LKK1070 and 1125SHP1127 substitutions also did not reduce LANA chromosome association or episome persistence. However, when N-terminal LANA binding to chromosomes was modestly diminished, the substitutions in 1068LKK1070 and 1125SHP1127 dramatically reduced both LANA chromosome association and episome persistence. These data suggest a model in which N- and C-terminal LANA cooperatively associates with chromosomes to mediate full-length LANA chromosome binding and viral persistence.

CLINICAL CONFERENCE

PEDIATRICS ◽  
1957 ◽  
Vol 20 (4) ◽  
pp. 740-746
Author(s):  
Melvin M. Grumbach
Keyword(s):  
Sex Difference ◽  
Sex Chromosome ◽  
Good Evidence ◽  
Polymorphonuclear Neutrophils ◽  
Vaginal Mucosa ◽  
Simple Method ◽  
X Chromosomes ◽  
Cytologic Examination ◽  
Sex Development ◽  
Sex Chromatin

Dr. Grumbach: Barr and associates have demonstrated that in the human the majority of somatic cells of females contain a conspicuous, heterochromatic mass of chromatin in the resting nuclei. Their discovery of a sex-difference in intermitotic nuclei of a number of vertebrate species, including man, has provided a relatively simple method for assessing the sex-chromosome constitution. This chromatin mass is about 1 micron in diameter and often plano-convex in configuration. It is usually located against the inner surface of the nuclear membrane and contains desoxyribonucleic acid. In males, a comparable chromatin mass is rarely found, never in more than a few per cent of the nuclei. There is good evidence that this so-called "sexchromatin" represents the fusion of heterochromatic portions of two X-chromosomes. The sex chromatin can be conveniently determined by examination of specimens of skin obtained by biopsy (Fig. 1). Recently, more practical methods for determining cytologic sex have been described employing smears from readily available tissues, such as the oral and vaginal mucosa (Fig. 2) and the blood. Davidson and Smith have shown that there is a sex difference in the morphology of polymorphonuclear neutrophils. Cytologic examination of chromosomal sex has provided an important tool for the investigation of anomalies of sex development. Apart from its ancillary role in diagnosis, cytologic examination of sex chromatin has made a significant contribution to our understanding of the disordered development in these afflictions. However, the results of this determination should not be regarded as an especial indication of the psychosexual orientation of patients with such abnormalities, nor, in the case of infants, of the sex to which they should be assigned.

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