Populational and Karyological Analysis of the Phytophilous Chironomid Endochironomus tendens F. (Diptera, Chironomidae). 1. New Chromosomal Sequences in the Species’ Karyotype Pool

The recent report of distinct Xanthomonas lineages of Xanthomonas arboricola pv. juglandis and Xanthomonas euroxanthea within the same walnut tree revealed that this consortium of walnut-associated Xanthomonas includes both pathogenic and nonpathogenic strains. As the implications of this co-colonization are still poorly understood, in order to unveil niche-specific adaptations, the genomes of three X. euroxanthea strains (CPBF 367, CPBF 424T, and CPBF 426) and of an X. arboricola pv. juglandis strain (CPBF 427) isolated from a single walnut tree in Loures (Portugal) were sequenced with two different technologies, Illumina and Nanopore, to provide consistent single scaffold chromosomal sequences. General genomic features showed that CPBF 427 has a genome similar to other X. arboricola pv. juglandis strains, regarding its size, number, and content of CDSs, while X. euroxanthea strains show a reduction regarding these features comparatively to X. arboricola pv. juglandis strains. Whole genome comparisons revealed remarkable genomic differences between X. arboricola pv. juglandis and X. euroxanthea strains, which translates into different pathogenicity and virulence features, namely regarding type 3 secretion system and its effectors and other secretory systems, chemotaxis-related proteins, and extracellular enzymes. Altogether, the distinct genomic repertoire of X. euroxanthea may be particularly useful to address pathogenicity emergence and evolution in walnut-associated Xanthomonas.

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CHROMOSOMAL SEQUENCES AND INTERISLAND COLONIZATIONS IN HAWAIIAN DROSOPHILA

Genetics ◽

10.1093/genetics/103.3.465 ◽

1983 ◽

Vol 103 (3) ◽

pp. 465-482

Author(s):

Hampton L Carson

Keyword(s):

Polytene Chromosomes ◽

Complex Species ◽

Hawaiian Drosophila ◽

On This Island ◽

Break Points ◽

Chromosomal Sequences ◽

Founder Events ◽

Paracentric Inversions ◽

Single Set

ABSTRACT Of 103 picture-winged Drosophila species endemic to the high Hawaiian islands, all but three are endemic to single islands or island complexes. They are presumed to have evolved in situ on each island. The banding pattern sequences of the five major polytene chromosomes of these species have been mapped to a single set of Standard sequences. Sequential variation among these chromosomes is due to 213 paracentric inversions. An atlas of their break points is provided. Geographical, morphological and behavioral data may be used to supplement the cytological information in tracing ancestry. Starting at the newer end of the archipelago, the 26 species of the Island of Hawaii (less than 700,000 years old) are inferred to have been derived from 19 founders, 15 from the Maui complex, three from Oahu and one from Kauai. The existence of 40 Maui complex species is explicable as resulting from 12 founders, ten from Oahu and two from Kauai. The 29 Oahu species can be explained by 12 founder events, five from Kauai and seven from Maui complex (summary in Figure 5). Although the ancestry of two Kauai species can be traced to newer islands, the ten remaining ones on this island (age about 5.6 million years) are apparently ancient elements in the fauna, relating ultimately to Palearctic continental sources.

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Karyological analysis of bitter gourd (Momordica charantia L., Cucurbitaceae) from Southeast Asian countries

Plant Genetic Resources ◽

10.1017/s1479262120000155 ◽

2020 ◽

Vol 18 (3) ◽

pp. 200-200

Author(s):

Nadia Kausar ◽

Zubaida Yousaf ◽

Afifa Younas ◽

Hafiza Sadia Ahmed ◽

Madiha Rashid ◽

...

Keyword(s):

Southeast Asian ◽

Momordica Charantia ◽

Bitter Gourd ◽

Asian Countries ◽

Karyological Analysis ◽

Southeast Asian Countries

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Ability of structurally related polycyclic aromatic carcinogens to induce homologous recombination between duplicated chromosomal sequences in mouse L cells

Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis ◽

10.1016/0027-5107(89)90003-1 ◽

1989 ◽

Vol 211 (2) ◽

pp. 205-214 ◽

Cited By ~ 14

Author(s):

Nitai P. Bhattacharyya ◽

Veronica M. Maher ◽

J.Justin McCormick

Keyword(s):

Homologous Recombination ◽

L Cells ◽

Polycyclic Aromatic ◽

Chromosomal Sequences

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Cloning and characterization of small circular DNA from Chinese hamster ovary cells.

Molecular and Cellular Biology ◽

10.1128/mcb.4.1.173 ◽

1984 ◽

Vol 4 (1) ◽

pp. 173-180 ◽

Cited By ~ 32

Author(s):

S W Stanfield ◽

D R Helinski

Keyword(s):

Chinese Hamster Ovary ◽

Cho Cells ◽

Chinese Hamster Ovary Cells ◽

Chinese Hamster ◽

Single Copy ◽

Chromosomal Dna ◽

Cho Cell ◽

Ovary Cells ◽

Chromosomal Sequences

Small polydisperse circular (spc) DNA was isolated and cloned, using BglII from Chinese hamster ovary (CHO) cells. The properties of 47 clones containing at least 43 different BglII fragments are reported. The majority of the clones probably contain entire sequences from individual spcDNA molecules. Most of the clones were homologous to sequences in CHO cell chromosomal DNA, and many were also homologous to mouse LMTK- cell chromosomal sequences. The majority of homologous CHO cell chromosomal sequences were repetitive, although a few may be single copy. Only a small fraction of cloned spcDNA molecules were present in every cell; most occurred less frequently than once in 15 cells. Localization studies indicated that at least a portion of spcDNA is associated with the nucleus in CHO cells.

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On the role of germ cells in planarian regeneration

Development ◽

10.1242/dev.55.1.53 ◽

1980 ◽

Vol 55 (1) ◽

pp. 53-63

Author(s):

V. Gremigni ◽

C. Miceli ◽

I. Puccinelli

Keyword(s):

Chromosome Number ◽

Germ Cells ◽

Primordial Germ Cells ◽

Karyological Analysis ◽

Blastema Formation ◽

Planarian Regeneration ◽

Somatic Tissues ◽

Caudal Area ◽

Complete Regeneration

Specimens from a polyploid biotype of Dugesia lugubris s.l. were used to clarify the role and fate of germ cells during planarian regeneration. These specimens provide a useful karyological marker because embryonic and somatic cells (3n = 12) can be easily distinguished from male (2n = 8) and female (6n = 24) germ cells by their chromosome number. We succeed in demonstrating how primordial germ cells participate in blastema formation and take part in rebuilding somatic tissues. This evidence was obtained by cutting each planarian specimen twice at appropriate levels. The first aimed to induce primordial germ cells to migrate to the wound. The second cut was performed after complete regeneration and aimed to obtain a blastema from a cephalic or caudal area devoid of gonads. A karyological analysis of mitotic cells present in each blastema obtained after the second cut provided evidence that cells, originally belonging to the germ lines, are still present in somatic tissues even months after complete regeneration. The role of primordial germ cells in planarian regeneration was finally discussed in relation to the phenomenon of metaplasia or transdifferentiation.

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Gene replacement with one-sided homologous recombination

Molecular and Cellular Biology ◽

10.1128/mcb.12.1.360-367.1992 ◽

1992 ◽

Vol 12 (1) ◽

pp. 360-367

Author(s):

N Berinstein ◽

N Pennell ◽

C A Ottaway ◽

M J Shulman

Keyword(s):

Homologous Recombination ◽

Dna Sequences ◽

Mammalian Cells ◽

Target Gene ◽

Gene Replacement ◽

Immunoglobulin Genes ◽

Nonhomologous Recombination ◽

Immunoglobulin Locus ◽

Chromosomal Sequences ◽

Dna Vectors

Homologous recombination is now routinely used in mammalian cells to replace endogenous chromosomal sequences with transferred DNA. Vectors for this purpose are traditionally constructed so that the replacement segment is flanked on both sides by DNA sequences which are identical to sequences in the chromosomal target gene. To test the importance of bilateral regions of homology, we measured recombination between transferred and chromosomal immunoglobulin genes when the transferred segment was homologous to the chromosomal gene only on the 3' side. In each of the four recombinants analyzed, the 5' junction was unique, suggesting that it was formed by nonhomologous, i.e., random or illegitimate, recombination. In two of the recombinants, the 3' junction was apparently formed by homologous recombination, while in the other two recombinants, the 3' junction as well as the 5' junction might have involved a nonhomologous crossover. As reported previously, we found that the frequency of gene targeting increases monotonically with the length of the region of homology. Our results also indicate that targeting with fragments bearing one-sided homology can be as efficient as with fragments with bilateral homology, provided that the overall length of homology is comparable. The frequency of these events suggests that the immunoglobulin locus is particularly susceptible to nonhomologous recombination. Vectors designed for one-sided homologous recombination might be advantageous for some applications in genetic engineering.

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