scholarly journals Unprecedented reorganization of holocentric chromosomes provides insights into the enigma of lepidopteran chromosome evolution

2019 ◽  
Vol 5 (6) ◽  
pp. eaau3648 ◽  
Author(s):  
Jason Hill ◽  
Pasi Rastas ◽  
Emily A. Hornett ◽  
Ramprasad Neethiraj ◽  
Nathan Clark ◽  
...  
Keyword(s):  
Chromosome Number ◽  
Chromosome Evolution ◽  
Chromosome Structure ◽  
Holocentric Chromosomes ◽  
Chromosome Counts ◽  
Pieris Napi ◽  
Haploid Chromosome Number ◽  
Genome Wide ◽  
The Face ◽  
Chromosome Level

Chromosome evolution presents an enigma in the mega-diverse Lepidoptera. Most species exhibit constrained chromosome evolution with nearly identical haploid chromosome counts and chromosome-level gene collinearity among species more than 140 million years divergent. However, a few species possess radically inflated chromosomal counts due to extensive fission and fusion events. To address this enigma of constraint in the face of an exceptional ability to change, we investigated an unprecedented reorganization of the standard lepidopteran chromosome structure in the green-veined white butterfly (Pieris napi). We find that gene content in P. napi has been extensively rearranged in large collinear blocks, which until now have been masked by a haploid chromosome number close to the lepidopteran average. We observe that ancient chromosome ends have been maintained and collinear blocks are enriched for functionally related genes suggesting both a mechanism and a possible role for selection in determining the boundaries of these genome-wide rearrangements.

scholarly journals Cryptic, extensive and non-random chromosome reorganization revealed by a butterfly chromonome

2017 ◽  
Author(s):  
Jason Hill ◽  
Pasi Rastas ◽  
Emil A. Hornett ◽  
Ramprasad Neethiraj ◽  
Nathan Clark ◽  
...  
Keyword(s):  
Chromosome Evolution ◽  
Chromosome Structure ◽  
Chromosomal Evolution ◽  
Holocentric Chromosomes ◽  
Structural Constraints ◽  
Chromosome Counts ◽  
Pieris Napi ◽  
Haploid Chromosome Number ◽  
Shared Gene ◽  
Chromosome Level

AbstractChromosome evolution, an important component of mico- and macroevolutionary dynamics 1–5, presents an enigma in the mega-diverse Lepidoptera6. While most species exhibit constrained chromosome evolution, with nearly identical haploid chromosome counts and chromosome-level shared gene content and collinearity among species despite more than 140 Million years of divergence7, a small fraction of species independently exhibit dramatic changes in chromosomal count due to extensive fission and fusion events that are facilitated by their holocentric chromosomes7–9. Here we address this enigma of simultaneous conservation and dynamism in chromosome evolution in our analysis of the chromonome (chromosome level assembly10) of the green-veined white butterfly, Pieris napi (Pieridae, Linnaeus, 1758). We report an unprecedented reorganization of the standard Lepidopteran chromosome structure via more than 90 fission and fusion events that are cryptic at other scales, as the haploid chromosome number is identical to related genera and gene collinearity within the large rearranged segments matches other Lepidoptera. Furthermore, these rearranged segments are significantly enriched for clusters of functionally related genes and the maintenance of ancient telomeric ends. These results suggest an unexpected role for selection in shaping chromosomal evolution when the structural constraints of monocentricq chromosomes are relaxed.

The chromosome numbers of five North American and European leech species

1987 ◽  
Vol 65 (3) ◽  
pp. 681-684 ◽  
Author(s):  
Ronald W. Davies ◽  
R. N. Singhal
Keyword(s):  
Chromosome Number ◽  
North American ◽  
Chromosome Numbers ◽  
Chromosome Evolution ◽  
Chromosome Counts ◽  
Prophase I ◽  
Metaphase I

Chromosome counts were obtained for four glossiphoniid species belonging to three genera (Glossiphonia, Theromyzon, Placobdella) and for one erpobdellid species (Dina lineata) of freshwater leeches. Theromyzon rude, which has a Palaearctic distribution, had seven bivalents at prophase I and metaphase I, while the Holarctic T. tessulatum had eight bivalents, giving diploid chromosome numbers of 14 and 16, respectively. Placobdella papillifera from Alberta had a chromosome number of 2n = 24 and Glossiphonia complanata from Alberta and England had chromosome counts of 2n = 28. At prophase I and metaphase I nine bivalents occurred in the majority of the nuclei of Dina lineata. These findings are discussed in relation to the chromosome evolution and phylogenetic schemes proposed by previous authors.

Recherches sur les Alaria (Phaeophyceae) de l'est canadien. I. Nombres chromosomiques et identité des Alaria de l'estuaire du St-Laurent

1974 ◽  
Vol 52 (4) ◽  
pp. 691-694 ◽  
Author(s):  
M.-J. Feller-Demalsy ◽  
P. Demalsy
Keyword(s):  
Chromosome Number ◽  
Single Species ◽  
Chromosome Counts ◽  
Eastern Canada ◽  
Lawrence Estuary ◽  
Haploid Chromosome Number ◽  
Biosystematic Study ◽  
Alaria Esculenta ◽  
St Lawrence Estuary

Chromosome counts in gametophytes and sporophylls of Alaria collected in the St. Lawrence Estuary show that all the specimens of this genus in eastern Canada may not belong to the single species A. esculenta Greville. Indeed, the haploid chromosome number (n) found in these algae is equal to half of the number attributed in the literature to Alaria esculenta from the British coasts. Three hypotheses for the interpretation of these observations are considered. The solution of the problem of the identity of Alaria can only be hoped for from their global, morphological, and biosystematic study.

scholarly journals Animal chromosome counts reveal similar range of chromosome numbers but with less polyploidy in animals compared to flowering plants

2020 ◽  
Author(s):  
Cristian Román-Palacios ◽  
Cesar A. Medina ◽  
Shing H. Zhan ◽  
Michael S. Barker
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Chromosome Evolution ◽  
Chromosome Count ◽  
Flowering Plants ◽  
Similar Distribution ◽  
Chromosome Counts ◽  
Remarkable Similarity ◽  
Similar Range

AbstractUnderstanding the mechanisms that underlie chromosome evolution may provide insights into the processes underpinning the origin, persistence, and evolutionary tempo of lineages. Here we present the first database of chromosome counts for animals (the Animal Chromosome Count database, ACC) summarizing chromosome numbers for ∼18,000 species. We found remarkable similarity in the distribution of chromosome counts between animals and flowering plants. At larger timescales, selection towards a specific range might explain the similar distribution of chromosome counts between these two groups. Nevertheless, changes in chromosome number are still potential drivers of divergence among species at shorter timescales. We also found that while animals and plants exhibit similar frequencies of speciation-related changes in chromosome number, plant speciation is more often related to changes in ploidy. Based on the ACC, our analyses suggest that changes in chromosome number alone could help explain patterns of diversity within animal clades.

scholarly journals The genome sequence of the lesser marbled fritillary, Brenthis ino, and evidence for a segregating neo-Z chromosome

2021 ◽  
Author(s):  
Alexander Mackintosh ◽  
Dominik Laetsch ◽  
Tobias Baril ◽  
Robert Foster ◽  
Vlad Dincă ◽  
...  
Keyword(s):  
Chromosome Number ◽  
Genome Assembly ◽  
Chromosome Evolution ◽  
Population Genomics ◽  
The Other ◽  
Z Chromosome ◽  
Valuable Resource ◽  
Male Individual ◽  
Show Evidence ◽  
Chromosome Level

The lesser marbled fritillary, Brenthis ino (Rottemburg, 1775), is a species of Palearctic butterfly. Male B. ino individuals have been reported to have between 12 and 14 pairs of chromosomes, a much reduced chromosome number than is typical in butterflies. Here we present a chromosome-level genome assembly for B. ino, as well as gene and transposable element annotations. The assembly is 411.8 Mb in span with contig and scaffold N50s of 9.6 and 29.5 Mb respectively. We also show evidence that the male individual from which we generated HiC data was heterozygous for a neo-Z chromosome, consistent with inheriting 14 chromosomes from one parent and 13 from the other. This genome assembly will be a valuable resource for studying chromosome evolution in Lepidoptera, as well as for comparative and population genomics more generally.

Gametangial meiosis in Phytophthora capsici

1976 ◽  
Vol 54 (13) ◽  
pp. 1535-1545 ◽  
Author(s):  
E. Sansome
Keyword(s):  
Chromosome Number ◽  
Phytophthora Capsici ◽  
Nuclear Size ◽  
Chromosome Size ◽  
Chromosome Counts ◽  
Haploid Chromosome Number ◽  
Zygote Nucleus ◽  
Gametangial Meiosis

The report of Stephenson et al. that the nuclear divisions in the gametangia of Phytophthora capsici are mitotic, resembling the divisions in the vegetative hyphae, was not confirmed. Pachytene, diplotene, and diakinesis stages were observed in the oogonia. Metaphase and anaphase were followed by a second division without any increase in nuclear and chromosome size between the two divisions. The haploid chromosome number is nine and an association of four chromosomes is present in one or both parents.The association of four chromosomes observed at diakinesis and metaphase is evidence that pairing of homologous parts occurs during the first division and is thus proof that the gametangial divisions are meiotic.There was no evidence of a prolonged prophase in the first division of the zygote nucleus and an eight-nucleate oospore showed no evidence of reduction in nuclear size or nuclear elimination such as would be required to account for the homokaryotic condition of single-oospore cultures on the hypothesis of zygotic meiosis.The problems involved in obtaining reliable chromosome counts from somatic nuclei are discussed.

scholarly journals Chromosome numbers of eight Carex taxa in Korea (Cyperaceae)

2021 ◽  
Vol 51 (3) ◽  
pp. 192-197
Author(s):  
Kyong-Sook CHUNG ◽  
Gyu Young CHUNG
Keyword(s):  
Species Diversity ◽  
Chromosome Number ◽  
Chromosome Numbers ◽  
Meiotic Chromosome ◽  
Holocentric Chromosomes ◽  
Basic Information ◽  
Chromosome Counts ◽  
High Species Diversity

In the flora of Korea, Carex L. is one of the most species-rich genera. Among nearly 157 Carex taxa, less than 30 have had their chromosome numbers reported. We report the meiotic chromosome numbers of eight Carex taxa from Korean populations, which include the first count for C. accrescens Ohwi (n = 37II) and the first chromosome investigations of Korean populations for three taxa: C. bostrychostigma Maxim. (n = 22II), C. lanceolata Boott (n = 36II), and C. paxii Kük. (n = 38II). In most species, chromosome counts observed in the study are included within the variation ranges of previous chromosome numbers. However, C. bostrychostigma Maxim. (n = 22II) and C. planiculmis Kom. (n = 29II) are assigned new chromosome numbers. Carex is known to have holocentric chromosomes, lacking visible primary constrictions and exhibiting great variance in its chromosome number. Further investigations of the diversity of Carex chromosomes will provide basic information with which to understand the high species diversity of the genus.

scholarly journals Limitation of current probe design for oligo-cross-FISH, exemplified by chromosome evolution studies in duckweeds

Chromosoma ◽  
2021 ◽  
Vol 130 (1) ◽  
pp. 15-25
Author(s):  
Phuong T. N. Hoang ◽  
Jean-Marie Rouillard ◽  
Jiří Macas ◽  
Ivona Kubalová ◽  
Veit Schubert ◽  
...  
Keyword(s):  
Growth Rate ◽  
Chromosome Number ◽  
Chromosome Evolution ◽  
Sequence Similarity ◽  
Flowering Plants ◽  
The Other ◽  
Probe Design ◽  
Congeneric Species ◽  
Specific Design ◽  
Spirodela Polyrhiza

AbstractDuckweeds represent a small, free-floating aquatic family (Lemnaceae) of the monocot order Alismatales with the fastest growth rate among flowering plants. They comprise five genera (Spirodela, Landoltia, Lemna, Wolffiella, and Wolffia) varying in genome size and chromosome number. Spirodela polyrhiza had the first sequenced duckweed genome. Cytogenetic maps are available for both species of the genus Spirodela (S. polyrhiza and S. intermedia). However, elucidation of chromosome homeology and evolutionary chromosome rearrangements by cross-FISH using Spirodela BAC probes to species of other duckweed genera has not been successful so far. We investigated the potential of chromosome-specific oligo-FISH probes to address these topics. We designed oligo-FISH probes specific for one S. intermedia and one S. polyrhiza chromosome (Fig. 1a). Our results show that these oligo-probes cross-hybridize with the homeologous regions of the other congeneric species, but are not suitable to uncover chromosomal homeology across duckweeds genera. This is most likely due to too low sequence similarity between the investigated genera and/or too low probe density on the target genomes. Finally, we suggest genus-specific design of oligo-probes to elucidate chromosome evolution across duckweed genera.

scholarly journals A long reads-based de-novo assembly of the genome of the Arlee homozygous line reveals chromosomal rearrangements in rainbow trout

2021 ◽  
Author(s):  
Guangtu Gao ◽  
Susana Magadan ◽  
Geoffrey C Waldbieser ◽  
Ramey C Youngblood ◽  
Paul A Wheeler ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Chromosome Number ◽  
Genome Assembly ◽  
De Novo Assembly ◽  
De Novo ◽  
Sequence Data ◽  
Structural Variations ◽  
High Coverage ◽  
Haploid Chromosome Number ◽  
Long Reads

Abstract Currently, there is still a need to improve the contiguity of the rainbow trout reference genome and to use multiple genetic backgrounds that will represent the genetic diversity of this species. The Arlee doubled haploid line was originated from a domesticated hatchery strain that was originally collected from the northern California coast. The Canu pipeline was used to generate the Arlee line genome de-novo assembly from high coverage PacBio long-reads sequence data. The assembly was further improved with Bionano optical maps and Hi-C proximity ligation sequence data to generate 32 major scaffolds corresponding to the karyotype of the Arlee line (2 N = 64). It is composed of 938 scaffolds with N50 of 39.16 Mb and a total length of 2.33 Gb, of which ∼95% was in 32 chromosome sequences with only 438 gaps between contigs and scaffolds. In rainbow trout the haploid chromosome number can vary from 29 to 32. In the Arlee karyotype the haploid chromosome number is 32 because chromosomes Omy04, 14 and 25 are divided into six acrocentric chromosomes. Additional structural variations that were identified in the Arlee genome included the major inversions on chromosomes Omy05 and Omy20 and additional 15 smaller inversions that will require further validation. This is also the first rainbow trout genome assembly that includes a scaffold with the sex-determination gene (sdY) in the chromosome Y sequence. The utility of this genome assembly is demonstrated through the improved annotation of the duplicated genome loci that harbor the IGH genes on chromosomes Omy12 and Omy13.

The early development of haploid and aneuploid parthenogenetic embryos

Development ◽  
1975 ◽  
Vol 34 (3) ◽  
pp. 645-655
Author(s):  
Matthew H. Kaufman ◽  
Leo Sachs
Keyword(s):  
Early Development ◽  
Polar Body ◽  
Chromosome Counts ◽  
Cell Stage ◽  
Haploid Chromosome Number ◽  
Stage Of Development ◽  
Morula Stage ◽  
Second Polar Body ◽  
Similar Development ◽  
Parthenogenetic Embryos

The early development of parthenogenetically activated oocytes has been studied in C57BL × CBA-T6T6 (F1T6) translocation heterozygote mice and C57BL × CBA-LAC (F1LAC) mice. All F1T6 oocytes had either a quadrivalent or a univalent-trivalent configuration at meiosis I; no such chromosome configurations were observed in the F1LAC oocytes. At ovulation 36·5 % of the F1T6 oocytes had 19 or 21 chromosomes, whereas 97 % of the F1LAC had the normal haploid chromosome number of 20. After parthenogenetic activation, chromosome counts at metaphase of the first cleavage mitosis were made of the eggs with a single pronucleus following extrusion of the second polar body. These activated eggs had similar frequencies of 19, 20 and 21 chromosomes as had the oocytes at ovulation. The activated 1-cell eggs were transferred to the oviducts of pseudopregnant recipients and the embryos recovered 3 days later. At this stage of development, most of the F1T6 embryos with 19 chromosomes were no longer found, but the frequency of 21-chromosome embryos was similar to the frequency of 21-chromosome oocytes and activated eggs. There was a similar mean number of cells in the embryos with 20 and 21 chromosomes. The results indicate that nearly all the embryos with 19 chromosomes failed to develop, probably beyond the 2-cell stage, whereas oocytes with 21 chromosomes had a similar development to oocytes with 20 chromosomes up to the morula stage.

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