Publications by authors named "Andrea Pedrosa Harand"

51 Publications

Oligo-FISH barcode in beans: a new chromosome identification system.

Theor Appl Genet 2021 Nov 8;134(11):3675-3686. Epub 2021 Aug 8.

Departamento de Genética, Universidade Federal de Pernambuco, Recife, PE, Brazil.

Key Message: An Oligo-FISH barcode system was developed for two model legumes, allowing the identification of all cowpea and common bean chromosomes in a single FISH experiment, and revealing new chromosome rearrangements. The FISH barcode system emerges as an effective tool to understand the chromosome evolution of economically important legumes and their related species. Current status on plant cytogenetic and cytogenomic research has allowed the selection and design of oligo-specific probes to individually identify each chromosome of the karyotype in a target species. Here, we developed the first chromosome identification system for legumes based on oligo-FISH barcode probes. We selected conserved genomic regions between Vigna unguiculata (Vu, cowpea) and Phaseolus vulgaris (Pv, common bean) (diverged ~ 9.7-15 Mya), using cowpea as a reference, to produce a unique barcode pattern for each species. We combined our oligo-FISH barcode pattern with a set of previously developed FISH probes based on BACs and ribosomal DNA sequences. In addition, we integrated our FISH maps with genome sequence data. Based on this integrated analysis, we confirmed two translocation events (involving chromosomes 1, 5, and 8; and chromosomes 2 and 3) between both species. The application of the oligo-based probes allowed us to demonstrate the participation of chromosome 5 in the translocation complex for the first time. Additionally, we detailed a pericentric inversion on chromosome 4 and identified a new paracentric inversion on chromosome 10. We also detected centromere repositioning associated with chromosomes 2, 3, 5, 7, and 9, confirming previous results for chromosomes 2 and 3. This first barcode system for legumes can be applied for karyotyping other Phaseolinae species, especially non-model, orphan crop species lacking genomic assemblies and cytogenetic maps, expanding our understanding of the chromosome evolution and genome organization of this economically important legume group.
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http://dx.doi.org/10.1007/s00122-021-03921-zDOI Listing
November 2021

A genome sequence resource for the genus Passiflora, the genome of the wild diploid species Passiflora organensis.

Plant Genome 2021 Jul 23:e20117. Epub 2021 Jul 23.

Dep. de Genética, Escola Superior de Agricultura "Luiz de Queiroz", Univ. de São Paulo, Piracicaba, 13418-900, Brazil.

The genus Passiflora comprises a large group of plants popularly known as passionfruit, much appreciated for their exotic flowers and edible fruits. The species (∼500) are morphologically variable (e.g., growth habit, size, and color of flowers) and are adapted to distinct tropical ecosystems. In this study, we generated the genome of the wild diploid species Passiflora organensis Gardner by adopting a hybrid assembly approach. Passiflora organensis has a small genome of 259 Mbp and a heterozygosity rate of 81%, consistent with its reproductive system. Most of the genome sequences could be integrated into its chromosomes with cytogenomic markers (satellite DNA) as references. The repeated sequences accounted for 58.55% of the total DNA analyzed, and the Tekay lineage was the prevalent retrotransposon. In total, 25,327 coding genes were predicted. Passiflora organensis retains 5,609 singletons and 15,671 gene families. We focused on the genes potentially involved in the locus determining self-incompatibility and the MADS-box gene family, allowing us to infer expansions and contractions within specific subfamilies. Finally, we recovered the organellar DNA. Structural rearrangements and two mitoviruses, besides relics of other mobile elements, were found in the chloroplast and mt-DNA molecules, respectively. This study presents the first draft genome assembly of a wild Passiflora species, providing a valuable sequence resource for genomic and evolutionary studies on the genus, and support for breeding cropped passionfruit species.
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http://dx.doi.org/10.1002/tpg2.20117DOI Listing
July 2021

Plastome evolution in the Caesalpinia group (Leguminosae) and its application in phylogenomics and populations genetics.

Planta 2021 Jul 8;254(2):27. Epub 2021 Jul 8.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife, Brazil.

Main Conclusion: The chloroplast genomes of Caesalpinia group species are structurally conserved, but sequence level variation is useful for both phylogenomic and population genetic analyses. Variation in chloroplast genomes (plastomes) has been an important source of information in plant biology. The Caesalpinia group has been used as a model in studies correlating ecological and genomic variables, yet its intergeneric and infrageneric relationships are not fully solved, despite densely sampled phylogenies including nuclear and plastid loci by Sanger sequencing. Here, we present the de novo assembly and characterization of plastomes from 13 species from the Caesalpinia group belonging to eight genera. A comparative analysis was carried out with 13 other plastomes previously available, totalizing 26 plastomes and representing 15 of the 26 known Caesalpinia group genera. All plastomes showed a conserved quadripartite structure and gene repertoire, except for the loss of four ndh genes in Erythrostemon gilliesii. Thirty polymorphic regions were identified for inter- or intrageneric analyses. The 26 aligned plastomes were used for phylogenetic reconstruction, revealing a well-resolved topology, and dividing the Caesalpinia group into two fully supported clades. Sixteen microsatellite (cpSSR) loci were selected from Cenostigma microphyllum for primer development and at least two were cross-amplified in different Leguminosae subfamilies by in vitro or in silico approaches. Four loci were used to assess the genetic diversity of C. microphyllum in the Brazilian Caatinga. Our results demonstrate the structural conservation of plastomes in the Caesalpinia group, offering insights into its systematics and evolution, and provides new genomic tools for future phylogenetic, population genetics, and phylogeographic studies.
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http://dx.doi.org/10.1007/s00425-021-03655-8DOI Listing
July 2021

Aiming off the target: recycling target capture sequencing reads for investigating repetitive DNA.

Ann Bot 2021 11;128(7):835-848

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife-PE, Brazil.

Background And Aims: With the advance of high-throughput sequencing, reduced-representation methods such as target capture sequencing (TCS) emerged as cost-efficient ways of gathering genomic information, particularly from coding regions. As the off-target reads from such sequencing are expected to be similar to genome skimming (GS), we assessed the quality of repeat characterization in plant genomes using these data.

Methods: Repeat composition obtained from TCS datasets of five Rhynchospora (Cyperaceae) species were compared with GS data from the same taxa. In addition, a FISH probe was designed based on the most abundant satellite found in the TCS dataset of Rhynchospora cephalotes. Finally, repeat-based phylogenies of the five Rhynchospora species were constructed based on the GS and TCS datasets and the topologies were compared with a gene-alignment-based phylogenetic tree.

Key Results: All the major repetitive DNA families were identified in TCS, including repeats that showed abundances as low as 0.01 % in the GS data. Rank correlations between GS and TCS repeat abundances were moderately high (r = 0.58-0.85), increasing after filtering out the targeted loci from the raw TCS reads (r = 0.66-0.92). Repeat data obtained by TCS were also reliable in developing a cytogenetic probe of a new variant of the holocentromeric satellite Tyba. Repeat-based phylogenies from TCS data were congruent with those obtained from GS data and the gene-alignment tree.

Conclusions: Our results show that off-target TCS reads can be recycled to identify repeats for cyto- and phylogenomic investigations. Given the growing availability of TCS reads, driven by global phylogenomic projects, our strategy represents a way to recycle genomic data and contribute to a better characterization of plant biodiversity.
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http://dx.doi.org/10.1093/aob/mcab063DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8577205PMC
November 2021

BAC- and oligo-FISH mapping reveals chromosome evolution among Vigna angularis, V. unguiculata, and Phaseolus vulgaris.

Chromosoma 2021 09 28;130(2-3):133-147. Epub 2021 Apr 28.

Departamento de Genética, Universidade Federal de Pernambuco, Recife, PE, Brazil.

Cytogenomic resources have accelerated synteny and chromosome evolution studies in plant species, including legumes. Here, we established the first cytogenetic map of V. angularis (Va, subgenus Ceratotropis) and compared this new map with those of V. unguiculata (Vu, subgenus Vigna) and P. vulgaris (Pv) by BAC-FISH and oligopainting approaches. We mapped 19 Vu BACs and 35S rDNA probes to the 11 chromosome pairs of Va, Vu, and Pv. Vigna angularis shared a high degree of macrosynteny with Vu and Pv, with five conserved syntenic chromosomes. Additionally, we developed two oligo probes (Pv2 and Pv3) used to paint Vigna orthologous chromosomes. We confirmed two reciprocal translocations (chromosomes 2 and 3 and 1 and 8) that have occurred after the Vigna and Phaseolus divergence (~9.7 Mya). Besides, two inversions (2 and 4) and one translocation (1 and 5) have occurred after Vigna and Ceratotropis subgenera separation (~3.6 Mya). We also observed distinct oligopainting patterns for chromosomes 2 and 3 of Vigna species. Both Vigna species shared similar major rearrangements compared to Pv: one translocation (2 and 3) and one inversion (chromosome 3). The sequence synteny identified additional inversions and/or intrachromosomal translocations involving pericentromeric regions of both orthologous chromosomes. We propose chromosomes 2 and 3 as hotspots for chromosomal rearrangements and de novo centromere formation within and between Vigna and Phaseolus. Our BAC- and oligo-FISH mapping contributed to physically trace the chromosome evolution of Vigna and Phaseolus and its application in further studies of both genera.
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http://dx.doi.org/10.1007/s00412-021-00758-9DOI Listing
September 2021

Large vs small genomes in Passiflora: the influence of the mobilome and the satellitome.

Planta 2021 Apr 1;253(4):86. Epub 2021 Apr 1.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife, Pernambuco, Brazil.

Main Conclusions: While two lineages of retrotransposons were more abundant in larger Passiflora genomes, the satellitome was more diverse and abundant in the smallest genome analysed. Repetitive sequences are ubiquitous and fast-evolving elements responsible for size variation and large-scale organization of plant genomes. Within Passiflora genus, a tenfold variation in genome size, not attributed to polyploidy, is known. Here, we applied a combined in silico and cytological approach to study the organization and diversification of repetitive elements in three species of this genus representing its known range in genome size variation. Sequences were classified in terms of type and repetitiveness and the most abundant were mapped to chromosomes. We identified long terminal repeat (LTR) retrotransposons as the most abundant elements in the three genomes, showing a considerable variation among species. Satellite DNAs (satDNAs) were less representative, but highly diverse between subgenera. Our results clearly confirm that the largest genome species (Passiflora quadrangularis) presents a higher accumulation of repetitive DNA sequences, specially Angela and Tekay elements, making up most of its genome. Passiflora cincinnata, with intermediate genome and from the same subgenus, showed similarity with P. quadrangularis regarding the families of repetitive DNA sequences, but in different proportions. On the other hand, Passiflora organensis, the smallest genome, from a different subgenus, presented greater diversity and the highest proportion of satDNA. Altogether, our data indicates that while large genomes evolved by an accumulation of retrotransposons, the smallest genome known for the genus has evolved by diversification of different repeat types, particularly satDNAs.
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http://dx.doi.org/10.1007/s00425-021-03598-0DOI Listing
April 2021

Multiple and independent rearrangements revealed by comparative cytogenetic mapping in the dysploid Leptostachyus group (Phaseolus L., Leguminosae).

Chromosome Res 2020 12 16;28(3-4):395-405. Epub 2020 Nov 16.

Laboratório de Citogenética e Evolução Vegetal, Departamento de Botânica, Universidade Federal de Pernambuco - UFPE, R. Prof. Moraes Rego, s/n, CDU, Recife, PE, 50670-420, Brazil.

Polyploidy and dysploidy have been reported as the main events in karyotype evolution of plants. In the genus Phaseolus L. (2n = 22), a small monophyletic group of three species, the Leptostachyus group, presents a dysploid karyotype with 2n = 20. It was shown in Phaseolus leptostachyus that the dysploidy was caused by a nested chromosome fusion (NCF) accompanied by several translocations, suggesting a high rate of karyotype evolution in the group. To verify if this karyotype restructuring was a single event or occurred progressively during the evolution of this group, we analysed P. macvaughii, sister to Phaseolus micranthus + P. leptostachyus. Twenty-four genomic clones of P. vulgaris previously mapped on P. leptostachyus, in addition to the 5S and 35S rDNA probes, were used for fluorescence in situ hybridization. Only a single rearrangement was common to the two species: the nested chromosome fusion (NCF) involving chromosomes 10 and 11. The translocation of chromosome 2 is not the same found in P. leptostachyus, and pericentric inversions in chromosomed 3 and 4 were exclusive of P. macvaughii. The other rearrangements observed in P. leptostachyus were not shared with this species, suggesting that they occurred after the separation of these lineages. The presence of private rearrangements indicates a progressive accumulation of karyotype changes in the Leptostachyus group instead of an instant genome-wide repatterning.
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http://dx.doi.org/10.1007/s10577-020-09644-zDOI Listing
December 2020

How diverse is heterochromatin in the Caesalpinia group? Cytogenomic characterization of Erythrostemon hughesii Gagnon & G.P. Lewis (Leguminosae: Caesalpinioideae).

Planta 2020 Sep 12;252(4):49. Epub 2020 Sep 12.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Rua Nelson Chaves S/N, Cidade Universitaria, Recife, PE, 50670-420, Brazil.

Main Conclusion: Cytogenomic characterization of Erythrostemon hughesii reveals a heterogeneity of repeats in its subtelomeric heterochromatin. Comparative analyses with other Caesalpinia group species reveal a significant reduction in the abundance of Ty3-gypsy/Chromovirus Tekay retrotransposons during its evolution. In numerically stable karyotypes, repetitive DNA variability is one of the main causes of genome and chromosome variation and evolution. Species from the Caesalpinia group (Leguminosae) are karyotypically characterized by 2n = 24, with small chromosomes and highly variable CMA heterochromatin banding patterns that correlate with environmental variables. Erythrostemon hughesii differs from other species of the group examined to date for having subtelomeric CMA bands; this contrasts with most species in the group which have proximal bands. Here we analyse the repeatome of E. hughesii using genome skimming and chromosomal mapping approaches to characterize the identity of the most abundant repetitive elements and their physical location. The repetitive fraction of E. hughesii comprises 28.73% of the genome. The most abundant elements were retrotransposons (RT) with long terminal repeats (LTR-RT; 9.76%) and satellite DNAs (7.83%). Within the LTR-RTs, the most abundant lineages were: Ty1/copia-Ale (1%), Ty3/gypsy CRM (0.88%) and Ty3/gypsy Athila (0.75%). Using fluorescent in situ hybridization four satellite DNAs and several LTR-RT elements were shown to be present in most subtelomeric CMA bands. These results highlight how the repeatome in E. hughesii, a species from Oaxaca state in Mexico, is clearly distinct from Northeast Brazilian species of the Caesalpinia group, mainly due to its high diversity of repeats in its subtelomeric heterochromatic bands and low amount of LTR-RT Ty3/gypsy-Tekay elements. Comparative sequence analysis of Tekay elements from different species is congruent with a clade-specific origin of this LTR-RT after the divergence of the Caesalpinia group. We hypothesize that repeat-rich heterochromatin may play a role in leading to faster genomic divergence between individuals, increasing speciation and diversification.
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http://dx.doi.org/10.1007/s00425-020-03453-8DOI Listing
September 2020

Integration of mandarin () cytogenetic map with its genome sequence.

Genome 2020 Sep 6;63(9):437-444. Epub 2020 Aug 6.

Laboratório de Citogenética e Evolução Vegetal, Departamento de Botânica, Universidade Federal de Pernambuco - UFPE, Recife, PE, Brazil.

is an extremely important genus in terms of world fruit production. Despite its economic importance and the small genome sizes of its species (2 = 18, 1C = 430 ± 68 Mbp), entire genomic assemblies have only recently become available for some of its representatives. Together with the previous CMA/DAPI banding and fluorescence in situ hybridization (FISH) in the group, these data are important for understanding the complex relationships between its species and for assisting breeding programs. To anchor genomic data with the cytogenetic map of mandarin (), the parental species of several economically important hybrids such as sweet orange and clementine, 18 BAC (bacterial artificial chromosome) clones were used. Eleven clementine BACs were positioned by BAC-FISH, doubling the number of chromosome markers so far available for BAC-FISH in citrus. Additionally, six previously mapped BACs were end-sequenced, allowing, together with one BAC previously sequenced, their assignment to scaffolds and the subsequent integration of chromosomes and the genome assembly. This study therefore established correlations between mandarin scaffolds and chromosomes, allowing further structural genomic and comparative study with the sweet orange genome, as well as insights into the chromosomal evolution of the group.
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http://dx.doi.org/10.1139/gen-2020-0046DOI Listing
September 2020

Breaks of macrosynteny and collinearity among moth bean (Vigna aconitifolia), cowpea (V. unguiculata), and common bean (Phaseolus vulgaris).

Chromosome Res 2020 12 11;28(3-4):293-306. Epub 2020 Jul 11.

Departamento de Genética, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil.

Comparative cytogenetic mapping is a powerful approach to gain insights into genome organization of orphan crops, lacking a whole sequenced genome. To investigate the cytogenomic evolution of important Vigna and Phaseolus beans, we built a BAC-FISH (fluorescent in situ hybridization of bacterial artificial chromosome) map of Vigna aconitifolia (Vac, subgenus Ceratotropis), species with no sequenced genome, and compared with V. unguiculata (Vu, subgenus Vigna) and Phaseolus vulgaris (Pv) maps. Seventeen Pv BACs, eight Vu BACs, and 5S and 35S rDNA probes were hybridized in situ on the 11 Vac chromosome pairs. Five Vac chromosomes (Vac6, Vac7, Vac9, Vac10, and Vac11) showed conserved macrosynteny and collinearity between V. unguiculata and P. vulgaris. On the other hand, we observed collinearity breaks, identified by pericentric inversions involving Vac2 (Vu2), Vac4 (Vu4), and Vac3 (Pv3). We also detected macrosynteny breaks of translocation type involving chromosomes 1 and 8 of V. aconitifolia and P. vulgaris; 2 and 3 of V. aconitifolia and P. vulgaris; and 1 and 5 of V. aconitifolia and V. unguiculata. Considering our data and previous BAC-FISH studies, six chromosomes (1, 2, 3, 4, 5, and 8) are involved in major karyotype divergences between genera and five (1, 2, 3, 4, and 5) between Vigna subgenera, including mechanisms such as duplications, inversions, and translocations. Macrosynteny breaks between Vigna and Phaseolus suggest that the major chromosomal rearrangements have occurred within the Vigna clade. Our cytogenomic comparisons bring new light on the degree of shared macrosynteny and mechanisms of karyotype diversification during Vigna and Phaseolus evolution.
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http://dx.doi.org/10.1007/s10577-020-09635-0DOI Listing
December 2020

Super-Resolution Microscopy Reveals Diversity of Plant Centromere Architecture.

Int J Mol Sci 2020 May 15;21(10). Epub 2020 May 15.

Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, 06466 Seeland, Germany.

Centromeres are essential for proper chromosome segregation to the daughter cells during mitosis and meiosis. Chromosomes of most eukaryotes studied so far have regional centromeres that form primary constrictions on metaphase chromosomes. These monocentric chromosomes vary from point centromeres to so-called "meta-polycentromeres", with multiple centromere domains in an extended primary constriction, as identified in and species. However, in various animal and plant lineages centromeres are distributed along almost the entire chromosome length. Therefore, they are called holocentromeres. In holocentric plants, centromere-specific proteins, at which spindle fibers usually attach, are arranged contiguously (line-like), in clusters along the chromosomes or in bands. Here, we summarize findings of ultrastructural investigations using immunolabeling with centromere-specific antibodies and super-resolution microscopy to demonstrate the structural diversity of plant centromeres. A classification of the different centromere types has been suggested based on the distribution of spindle attachment sites. Based on these findings we discuss the possible evolution and advantages of holocentricity, and potential strategies to segregate holocentric chromosomes correctly.
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http://dx.doi.org/10.3390/ijms21103488DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7278974PMC
May 2020

Diversity of repetitive sequences within compact genomes of Phaseolus L. beans and allied genera Cajanus L. and Vigna Savi.

Chromosome Res 2020 06 16;28(2):139-153. Epub 2019 Nov 16.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Av. Prof. Moraes Rêgo, s/n, Cidade Universitária, Recife, PE, 50670420, Brazil.

Repetitive sequences are ubiquitous and fast-evolving elements responsible for size variation and large-scale organization of plant genomes. Within tribe Phaseoleae (Fabaceae), some genera, such as Phaseolus, Vigna, and Cajanus, show small genome and mostly stable chromosome number. Here, we applied a combined computational and cytological approach to study the organization and diversification of repetitive elements in some species of these genera. Sequences were classified in terms of type and repetitiveness and the most abundant were mapped to chromosomes. We identified long terminal repeat (LTR) retrotransposons, especially Ogre and Chromovirus elements, making up most of genomes, other than P. acutifolius and Vigna species. Satellite DNAs (SatDNAs) were less representative, but highly diverse among species, showing a clear phylogenetic relationship. In situ localization revealed preferential location at pericentromeres and centromeres for both types of sequences, suggesting a heterogeneous composition, especially for centromeres. Few elements showed subterminal accumulation. Copy number variation among chromosomes within and among species was observed for all nine identified SatDNAs. Altogether, our data pointed two main elements (Ty3/Gypsy retrotransponsons and SatDNAs) to the diversification on the repetitive landscape in Phaseoleae, with a typical set of repeats in each species. The high turnover of these sequences, however, did not affect total genome size.
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http://dx.doi.org/10.1007/s10577-019-09618-wDOI Listing
June 2020

Evolutionary convergence or homology? Comparative cytogenomics of Caesalpinia group species (Leguminosae) reveals diversification in the pericentromeric heterochromatic composition.

Planta 2019 Dec 6;250(6):2173-2186. Epub 2019 Nov 6.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Rua Nelson Chaves S/N, Cidade Universitária, Recife, PE, 50670-420, Brazil.

Main Conclusion: We demonstrated by cytogenomic analysis that the proximal heterochromatin of the Northeast Brazilian species of Caesalpinia group is enriched with phylogenetically conserved Ty3/Gypsy-Tekay RT, but diverge in the presence of Ty3/Gypsy-Athila RT and satDNA. The Caesalpinia Group includes 225 species and 27 monophyletic genera of which four occur in Northeastern Brazil: Erythrostemon (1 sp.), Cenostigma (7 spp.), Libidibia (1 sp.), and Paubrasilia (1 sp.). The last three genera are placed in different clades in the Caesalpinia Group phylogeny, and yet they are characterized by having a numerically stable karyotype 2n = 24 (16 M+8A) and GC-rich heterochromatic bands (chromomycin A positive/CMA bands) in the proximal chromosome regions. To characterize the composition of their heterochromatin and test for the homology of these chromosomal regions, genomic DNA was extracted from Cenostigma microphyllum, Libidibia ferrea, and Paubrasilia echinata, and sequenced at low coverage using the Illumina platform. The genomic repetitive fractions were characterized using a Galaxy/RepeatExplorer-Elixir platform. The most abundant elements of each genome were chromosomally located by fluorescent in situ hybridization (FISH) and compared to the CMA heterochromatin distribution. The repetitive fraction of the genomes of C. microphyllum, L. ferrea, and P. echinata were estimated to be 41.70%, 38.44%, and 72.51%, respectively. Ty3/Gypsy retrotransposons (RT), specifically the Tekay lineage, were the most abundant repeats in each of the three genomes. FISH mapping revealed species-specific patterns for the Tekay elements in the proximal regions of the chromosomes, co-localized with CMA bands. Other species-specific patterns were observed, e.g., for the Ty3/Gypsy RT Athila elements which were found in all the proximal heterochromatin of L. ferrea or restricted to the acrocentric chromosomes of C. microphyllum. This Athila labeling co-localized with satellite DNAs (satDNAs). Although the Caesalpinia Group diverged around 55 Mya, our results suggest an ancestral colonization of Tekay RT in the proximal heterochromatin. Thus, the present-day composition of the pericentromeric heterochromatin in these Northeast Brazilian species is a combination of the maintenance of an ancestral Tekay distribution with a species-specific accumulation of other repeats.
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http://dx.doi.org/10.1007/s00425-019-03287-zDOI Listing
December 2019

Together But Different: The Subgenomes of the Bimodal Karyotypes Are Differentially Organized.

Front Plant Sci 2019 7;10:1170. Epub 2019 Oct 7.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife, Brazil.

Bimodal karyotypes are characterized by the presence of two sets of chromosomes of contrasting size. (2 = 12) presents a bimodal karyotype with a large chromosome pair, which has a pericentric inversion in permanent heterozygosity with suppressed recombination, and five pairs of three to four times smaller chromosomes. Aiming to understand whether high copy number sequence composition differs between both chromosome sets, we investigated the repetitive DNA fraction of and compared it to the chromosomal organization of the related species, not containing the pericentric inversion. We also compared the repetitive sequence proportions between the heteromorphic large chromosomes of and between and to understand the influence of the chromosome inversion on the dynamics of repetitive sequences. The most abundant repetitive families of the genome showed a similar chromosomal distribution in both homologs of the large pair and in both species, apparently not influenced by the species-specific inversions. The repeat families Ebusat1 and Ebusat4 are localized interstitially only on the large chromosome pair, while Ebusat2 is located in the centromeric region of all chromosomes. The four most abundant retrotransposon lineages are accumulated in the large chromosome pair. Replication timing and distribution of epigenetic and transcriptional marks differ between large and small chromosomes. The differential distribution of retroelements appears to be related to the bimodal condition and is not influenced by the nonrecombining chromosome inversions in these species. Thus, the large and small chromosome subgenomes of the bimodal karyotype are differentially organized and probably evolved by repetitive sequences accumulation on the large chromosome set.
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http://dx.doi.org/10.3389/fpls.2019.01170DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6791338PMC
October 2019

Identification of passion fruit (Passiflora edulis) chromosomes using BAC-FISH.

Chromosome Res 2019 12 18;27(4):299-311. Epub 2019 Jul 18.

Department of Botany, Federal University of Pernambuco, Recife, Brazil.

Passiflora edulis, the yellow passion fruit, is the main crop from the Passiflora genus, which comprises 525 species with its diversity center in South America. Genetic maps and a BAC (bacterial artificial chromosome) genomic library are available, but the nine chromosome pairs of similar size and morphology (2n = 18) hamper chromosome identification, leading to different proposed karyotypes. Thus, the aim of this study was to establish chromosome-specific markers for the yellow passion fruit using single-copy and repetitive sequences as probes in fluorescent in situ hybridizations (FISH) to allow chromosome identification and future integration with whole genome data. Thirty-six BAC clones harboring genes and three retrotransposons (Ty1-copy, Ty3-gypsy, and LINE) were selected. Twelve BACs exhibited a dispersed pattern similar to that revealed by retroelements, and one exhibited subtelomeric distribution. Twelve clones showed unique signals in terminal or subterminal regions of the chromosomes, allowing their genes to be anchored to six chromosome pairs that can be identified with single-copy markers. The markers developed herein will provide an important tool for genomic and evolutionary studies in the Passiflora genus.
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http://dx.doi.org/10.1007/s10577-019-09614-0DOI Listing
December 2019

Development of ten microsatellite markers for Alibertia edulis (Rubiaceae), a Brazilian savanna tree species.

Mol Biol Rep 2019 Aug 30;46(4):4593-4597. Epub 2019 Apr 30.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Centre of Biosciences, Federal University of Pernambuco, R. Prof. Moraes Rego, s/n, CDU, Recife, PE, 50670-420, Brazil.

Ten microsatellite markers were developed using next-generation sequencing data for Alibertia edulis (Rubiaceae), a widely distributed species typical of Cerrado (Brazilian savanna) vegetation. The markers were polymorphic in the two populations analyzed. The numbers of alleles, and observed (H) and expected (H) heterozygosities per polymorphic locus ranged from 2 to 11, 0.091 to 1.0, and 0.100 to 0.937 respectively. The SSR loci demonstrated moderate to high polymorphism values in both populations analyzed, with PIC values ranging from 0.26 to 0.91, and total allele numbers ranging from three to 16. The inbreeding coefficient values were generally higher in the Piauí population (ranging from - 0.593 to 0.762) than in the Mato Grosso population (ranging from - 1 to 0.575). The differences observed between those disjunct populations suggest they harbor different alleles, which has implications for Cerrado conservation strategies. Those loci will be useful for population studies of A. edulis.
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http://dx.doi.org/10.1007/s11033-019-04819-2DOI Listing
August 2019

Development and characterization of eleven microsatellite loci for the tropical understory tree Paypayrola blanchetiana Tul. (Violaceae).

Mol Biol Rep 2019 Apr 28;46(2):2529-2532. Epub 2019 Jan 28.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Center of Biosciences, Federal University of Pernambuco, R. Prof. Moraes Rego, s/n, CDU, Recife, PE, 50670-420, Brazil.

Microsatellites markers were developed for Paypayrola blanchetiana (Violaceae), a near-dispersing forest tree forming aggregated populations, to investigate genetic diversity and gene flow among subpopulations in a fragmented environment. Next generation sequencing (Illumina platform) was used to develop ten nuclear microsatellite loci and one plastid microsatellite locus that amplify in P. blanchetiana. Polymorphism was tested in two subpopulations separated by a distance of approximately 11 km. The identified loci contained between two and five alleles per locus. Observed heterozygosity ranged between 0.063 and 0.563 in both subpopulations, while expected heterozygosity ranged from 0.063 to 0.567 in the first, and 0.063-0.627 in the second subpopulation. The microsatellites are among the first in the family Violaceae and will be useful for population genetic studies in this species. Amplification was successful in one further Paypayrola species from Amazonia, which suggest a wider usefulness of the present markers.
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http://dx.doi.org/10.1007/s11033-019-04622-zDOI Listing
April 2019

Common Bean Subtelomeres Are Hot Spots of Recombination and Favor Resistance Gene Evolution.

Front Plant Sci 2018 14;9:1185. Epub 2018 Aug 14.

Institute of Plant Sciences Paris-Saclay (IPS2), UMR 9213/UMR1403, CNRS, INRA, Université Paris-Sud, Université d'Evry, Université Paris-Diderot Sorbonne Paris Cité, Orsay, France.

Subtelomeres of most eukaryotes contain fast-evolving genes usually involved in adaptive processes. In common bean (), the anthracnose resistance () locus corresponds to a cluster of nucleotide-binding-site leucine-rich-repeat (NL) encoding sequences, the prevalent class of plant genes. To study the recent evolution of this gene cluster, we used a combination of sequence, genetic and cytogenetic comparative analyses between common bean genotypes from two distinct gene pools (Andean and Mesoamerican) that diverged 0.165 million years ago. is a large subtelomeric cluster on chromosome 11 comprising from 32 (Mesoamerican) to 52 (Andean) NL sequences embedded within satellite repeats. Since the recent split between Andean and Mesoamerican gene pools, the cluster has experienced numerous gene-pool specific NL losses, leading to distinct NL repertoires. The high proportion of solo-LTR retrotransposons indicates that the cluster is located in a hot spot of unequal intra-strand homologous recombination. Furthermore, we observe large segmental duplications involving both Non-Homologous End Joining and Homologous Recombination double-strand break repair pathways. Finally, the identification of a Mesoamerican-specific subtelomeric sequence reveals frequent interchromosomal recombinations between common bean subtelomeres. Altogether, our results highlight that common bean subtelomeres are hot spots of recombination and favor the rapid evolution of genes. We propose that chromosome ends could act as gene incubators in many plant genomes.
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http://dx.doi.org/10.3389/fpls.2018.01185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6102362PMC
August 2018

Are holocentrics doomed to change? Limited chromosome number variation in Rhynchospora Vahl (Cyperaceae).

Protoplasma 2018 Jan 26;255(1):263-272. Epub 2017 Aug 26.

Departamento de Botânica, Centro de Biociências, Laboratório de Citogenética e Evolução Vegetal, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego, s/n, Cidade Universitária, Recife, PE, 50670-901, Brazil.

Karyotype evolution in species with non-localised centromeres (holocentric chromosomes) is usually very dynamic and associated with recurrent fission and fusion (also termed agmatoploidy/symploidy) events. In Rhynchospora (Cyperaceae), one of the most species-rich sedge genera, all analysed species have holocentric chromosomes and their numbers range from 2n = 4 to 2n = 84. Agmatoploidy/symploidy and polyploidy were suggested as the main processes in the reshuffling of Rhynchospora karyotypes, although testing different scenarios of chromosome number evolution in a phylogenetic framework has not been attempted until now. Here, we used maximum likelihood and model-based analyses, in combination with genome size estimation and ribosomal DNA distribution, to understand chromosome evolution in Rhynchospora. Overall, chromosome number variation showed a significant phylogenetic signal and the majority of the lineages maintained a karyotype of 2n = 10 (~48% of the species), the most likely candidate for the ancestral number of the genus. Higher and lower chromosome numbers were restricted to specific clades, whilst polyploidy and/or fusion/fission events were present in specific branches. Variation in genome size and ribosomal DNA site number showed no correlation with ploidy level or chromosome number. Although different mechanisms of karyotype evolution (polyploidy, fusion and fission) seem to be acting in distinct lineages, the degree of chromosome variation and the main mechanisms involved are comparable to those found in some monocentric genera and lower than expected for a holocentric genus.
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http://dx.doi.org/10.1007/s00709-017-1154-4DOI Listing
January 2018

Centromeric and non-centromeric satellite DNA organisation differs in holocentric Rhynchospora species.

Chromosoma 2017 03 19;126(2):325-335. Epub 2016 Sep 19.

Laboratory of Plant Cytogenetics and Evolution, Federal University of Pernambuco (UFPE), Recife, PE, Brazil.

Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R. tenuis) revealed linear signals at both chromatids, non-centromeric, species-specific satDNAs formed distinct clusters along the chromosomes. Colocalisation of both repeat types resulted in a ladder-like hybridisation pattern at mitotic chromosomes. In interphase, the centromeric satDNA was dispersed while non-centromeric satDNA clustered and partly colocalised to chromocentres. Despite the banding-like hybridisation patterns of the clustered satDNA, the identification of chromosome pairs was impaired due to the irregular hybridisation patterns of the homologues in R. tenuis and R. ciliata. These differences are probably caused by restricted or impaired meiotic recombination as reported for R. tenuis, or alternatively by complex chromosome rearrangements or unequal condensation of homologous metaphase chromosomes. Thus, holocentricity influences the chromosomal organisation leading to differences in the distribution patterns and condensation dynamics of centromeric and non-centromeric satDNA.
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http://dx.doi.org/10.1007/s00412-016-0616-3DOI Listing
March 2017

Holocentromere identity: from the typical mitotic linear structure to the great plasticity of meiotic holocentromeres.

Chromosoma 2016 Sep 16;125(4):669-81. Epub 2016 Aug 16.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife, Pernambuco, 50670-420, Brazil.

The centromere is the chromosomal site of kinetochore assembly and is responsible for the correct chromosome segregation during mitosis and meiosis in eukaryotes. Contrary to monocentrics, holocentric chromosomes lack a primary constriction, what is attributed to a kinetochore activity along almost the entire chromosome length during mitosis. This extended centromere structure imposes a problem during meiosis, since sister holocentromeres are not co-oriented during first meiotic division. Thus, regardless of the relatively conserved somatic chromosome structure of holocentrics, during meiosis holocentric chromosomes show different adaptations to deal with this condition. Recent findings in holocentrics have brought back the discussion of the great centromere plasticity of eukaryotes, from the typical CENH3-based holocentromeres to CENH3-less holocentric organisms. Here, we summarize recent and former findings about centromere/kinetochore adaptations shown by holocentric organisms during mitosis and meiosis and discuss how these adaptations are related to the type of meiosis found.
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http://dx.doi.org/10.1007/s00412-016-0612-7DOI Listing
September 2016

Developmental programmed cell death during asymmetric microsporogenesis in holocentric species of Rhynchospora (Cyperaceae).

J Exp Bot 2016 10 4;67(18):5391-5401. Epub 2016 Aug 4.

Laboratory of Cytogenetics and Plant Diversity, Department of General Biology, Center of Biological Sciences, State University of Londrina, Londrina 86057-970, Paraná, Brazil

Members of the Cyperaceae family exhibit an asymmetric microsporogenesis that results in the degeneration of three out of four meiotic products. Efforts have been made previously to describe the resulting structure, named the pseudomonad, but mechanisms concerning the establishment of cell domains, nuclear development, and programmed cell death are largely unknown. Using the Rhynchospora genus as a model, evidence for cell asymmetry, cytoplasmic isolation, and programmed cell death was obtained by a combination of electron microscopic, cytochemical, immunocytochemical, in situ hybridization, and flow cytometric methods. Degenerative cells were identified at the abaxial region, with the cytoskeleton marking their delimitation from the functional domain after meiosis. After attempting to initiate cell division with an unreplicated genome and abnormal spindle assembly, these cells exhibited a gradual process of cytoplasmic contraction associated with hypermethylation of cytosines and differential loss of DNA. These results indicate that the asymmetric tetrad establishes a functional cell, where one nucleus is preferentially selected to survive. Degenerative haploid cells are then eliminated in a multistep process associated with mitotic disorder, non-random elimination of repetitive DNA, vacuolar cell death, and DNA fragmentation.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5049389PMC
http://dx.doi.org/10.1093/jxb/erw300DOI Listing
October 2016

Restructuring of Holocentric Centromeres During Meiosis in the Plant Rhynchospora pubera.

Genetics 2016 Oct 3;204(2):555-568. Epub 2016 Aug 3.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, 50670-420 Recife, Pernambuco, Brazil

Centromeres are responsible for the correct segregation of chromosomes during mitosis and meiosis. Holocentric chromosomes, characterized by multiple centromere units along each chromatid, have particular adaptations to ensure regular disjunction during meiosis. Here we show by detecting CENH3, CENP-C, tubulin, and centromeric repeats that holocentromeres may be organized differently in mitosis and meiosis of Rhynchospora pubera Contrasting to the mitotic linear holocentromere organization, meiotic centromeres show several clusters of centromere units (cluster-holocentromeres) during meiosis I. They accumulate along the poleward surface of bivalents where spindle fibers perpendicularly attach. During meiosis II, the cluster-holocentromeres are mostly present in the midregion of each chromatid. A linear holocentromere organization is restored after meiosis during pollen mitosis. Thus, a not yet described case of a cluster-holocentromere organization, showing a clear centromere restructuration between mitosis and meiosis, was identified in a holocentric organism.
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http://dx.doi.org/10.1534/genetics.116.191213DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5068846PMC
October 2016

Evolutionary dynamics of satellite DNA repeats from Phaseolus beans.

Protoplasma 2017 Mar 22;254(2):791-801. Epub 2016 Jun 22.

Laboratório de Citogenética e Evolução Vegetal, Departamento de Botânica, Universidade Federal de Pernambuco, Recife, PE, Brazil.

Common bean (Phaseolus vulgaris) subtelomeres are highly enriched for khipu, the main satellite DNA identified so far in this genome. Here, we comparatively investigate khipu genomic organization in Phaseolus species from different clades. Additionally, we identified and characterized another satellite repeat, named jumper, associated to khipu. A mixture of P. vulgaris khipu clones hybridized in situ confirmed the presence of khipu-like sequences on subterminal chromosome regions in all Phaseolus species, with differences in the number and intensity of signals between species and when species-specific clones were used. Khipu is present as multimers of ∼500 bp and sequence analyses of cloned fragments revealed close relationship among khipu repeats. The new repeat, named jumper, is a 170-bp satellite sequence present in all Phaseolus species and inserted into the nontranscribed spacer (NTS) of the 5S rDNA in the P. vulgaris genome. Nevertheless, jumper was found as a high-copy repeat at subtelomeres and/or pericentromeres in the Phaseolus microcarpus lineage only. Our data argue for khipu as an important subtelomeric satellite DNA in the genus and for a complex satellite repeat composition of P. microcarpus subtelomeres, which also contain jumper. Furthermore, the differential amplification of these repeats in subtelomeres or pericentromeres reinforces the presence of a dynamic satellite DNA library in Phaseolus.
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http://dx.doi.org/10.1007/s00709-016-0993-8DOI Listing
March 2017

Speeding up chromosome evolution in Phaseolus: multiple rearrangements associated with a one-step descending dysploidy.

Chromosoma 2016 06 21;125(3):413-21. Epub 2015 Oct 21.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Rua Nelson Chaves s/n, Recife, PE, 50670-420, Brazil.

The genus Phaseolus L. has been subject of extensive cytogenetic studies due to its global economic importance. It is considered karyotypically stable, with most of its ca. 75 species having 2n = 22 chromosomes, and only three species (Phaseolus leptostachyus, Phaseolus macvaughii, and Phaseolus micranthus), which form the Leptostachyus clade, having 2n = 20. To test whether a simple chromosomal fusion was the cause of this descending dysploidy, mitotic chromosomes of P. leptostachyus (2n = 20) were comparatively mapped by fluorescent in situ hybridization (FISH) using bacterial artificial chromosomes (BACs) and ribosomal DNA (rDNA) probes. Our results corroborated the conservation of the 5S and 45S rDNA sites on ancestral chromosomes 10 and 6, respectively. The reduction from x = 11 to x = 10 was the result of the insertion of chromosome 10 into the centromeric region of chromosome 11, supporting a nested chromosome fusion (NCF) as the main cause of this dysploidy. Additionally, the terminal region of the long arm of chromosome 6 was translocated to this larger chromosome. Surprisingly, the NCF was accompanied by several additional translocations and inversions previously unknown for the genus, suggesting that the dysploidy may have been associated to a burst of genome reorganization in this otherwise stable, diploid plant genus.
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http://dx.doi.org/10.1007/s00412-015-0548-3DOI Listing
June 2016

Holocentromeres in Rhynchospora are associated with genome-wide centromere-specific repeat arrays interspersed among euchromatin.

Proc Natl Acad Sci U S A 2015 Nov 21;112(44):13633-8. Epub 2015 Oct 21.

Leibniz Institute of Plant Genetics and Crop Plant Research Gatersleben, 06466 Stadt Seeland, Germany;

Holocentric chromosomes lack a primary constriction, in contrast to monocentrics. They form kinetochores distributed along almost the entire poleward surface of the chromatids, to which spindle fibers attach. No centromere-specific DNA sequence has been found for any holocentric organism studied so far. It was proposed that centromeric repeats, typical for many monocentric species, could not occur in holocentrics, most likely because of differences in the centromere organization. Here we show that the holokinetic centromeres of the Cyperaceae Rhynchospora pubera are highly enriched by a centromeric histone H3 variant-interacting centromere-specific satellite family designated "Tyba" and by centromeric retrotransposons (i.e., CRRh) occurring as genome-wide interspersed arrays. Centromeric arrays vary in length from 3 to 16 kb and are intermingled with gene-coding sequences and transposable elements. We show that holocentromeres of metaphase chromosomes are composed of multiple centromeric units rather than possessing a diffuse organization, thus favoring the polycentric model. A cell-cycle-dependent shuffling of multiple centromeric units results in the formation of functional (poly)centromeres during mitosis. The genome-wide distribution of centromeric repeat arrays interspersing the euchromatin provides a previously unidentified type of centromeric chromatin organization among eukaryotes. Thus, different types of holocentromeres exist in different species, namely with and without centromeric repetitive sequences.
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http://dx.doi.org/10.1073/pnas.1512255112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4640781PMC
November 2015

Intra- and interchromosomal rearrangements between cowpea [Vigna unguiculata (L.) Walp.] and common bean (Phaseolus vulgaris L.) revealed by BAC-FISH.

Chromosome Res 2015 Jun 30;23(2):253-66. Epub 2015 Jan 30.

Departamento de Genética, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, Recife, PE, 50670-420, Brazil,

Cowpea (Vigna unguiculata) is an annual legume grown in tropical and subtropical regions, which is economically relevant due to high protein content in dried beans, green pods, and leaves. In this work, a comparative cytogenetic study between V. unguiculata and Phaseolus vulgaris (common bean) was conducted using BAC-FISH. Sequences previously mapped in P. vulgaris chromosomes (Pv) were used as probes in V. unguiculata chromosomes (Vu), contributing to the analysis of macrosynteny between both legumes. Thirty-seven clones from P. vulgaris 'BAT93' BAC library, corresponding to its 11 linkage groups, were hybridized in situ. Several chromosomal rearrangements were identified, such as translocations (between BACs from Pv1 and Pv8; Pv2 and Pv3; as well as Pv2 and Pv11), duplications (BAC from Pv3), as well as paracentric and pericentric inversions (BACs from Pv3, and Pv4, respectively). Two BACs (from Pv2 and Pv7), which hybridized at terminal regions in almost all P. vulgaris chromosomes, showed single-copy signal in Vu. Additionally, 17 BACs showed no signal in V. unguiculata chromosomes. The present results demonstrate the feasibility of using BAC libraries in comparative chromosomal mapping and karyotype evolution studies between Phaseolus and Vigna species, and revealed several macrosynteny and collinearity breaks among both legumes.
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http://dx.doi.org/10.1007/s10577-014-9464-2DOI Listing
June 2015

Low genetic diversity and high differentiation among relict populations of the neotropical gymnosperm Podocarpus sellowii (Klotz.) in the Atlantic Forest.

Genetica 2015 Feb 23;143(1):21-30. Epub 2014 Dec 23.

Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco (UFPE), Recife, PE, 50670-420, Brazil.

Podocarpus sellowii (Podocarpaceae) is one of only a few gymnosperms native to Brazil and the sole species of the genus found in the northeastern region of that country. It has a very restricted distribution in this region, with only three known populations in highland forests (called Brejos de Altitude), which apparently have been isolated from each other since the Pleistocene. Due to this long-term isolation and the fact that these populations have few adult individuals and suffer great anthropogenic pressure, low genetic variability is expected, compromising their long-term viability. The present work assessed the genetic variability and structure of northeastern populations of P. sellowii to investigate the role of Pleistocene glaciations on the genetic relationships between them and to propose strategies for their conservation by analyzing the SSR and ISSR markers of adult and juvenile individuals. Low genetic diversity was found with both markers, associated with a high differentiation of the Brejo de Baturité population in relation to the others-suggesting their isolation at different points in time, probably during the Pleistocene. Actions directed towards increasing the genetic diversity of these populations will be needed, such as planting seedlings with high genetic variability-but the high degrees of differentiation observed between the populations must be taken into account.
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http://dx.doi.org/10.1007/s10709-014-9809-yDOI Listing
February 2015

Chiasmatic and achiasmatic inverted meiosis of plants with holocentric chromosomes.

Nat Commun 2014 Oct 8;5:5070. Epub 2014 Oct 8.

Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Dr Bohr-Gasse 9, Vienna A-1030, Austria.

Meiosis is a specialized cell division in sexually reproducing organisms before gamete formation. Following DNA replication, the canonical sequence in species with monocentric chromosomes is characterized by reductional segregation of homologous chromosomes during the first and equational segregation of sister chromatids during the second meiotic division. Species with holocentric chromosomes employ specific adaptations to ensure regular disjunction during meiosis. Here we present the analysis of two closely related plant species with holocentric chromosomes that display an inversion of the canonical meiotic sequence, with the equational division preceding the reductional. In-depth analysis of the meiotic divisions of Rhynchospora pubera and R. tenuis reveals that during meiosis I sister chromatids are bi-oriented, display amphitelic attachment to the spindle and are subsequently separated. During prophase II, chromatids are connected by thin chromatin threads that appear instrumental for the regular disjunction of homologous non-sister chromatids in meiosis II.
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http://dx.doi.org/10.1038/ncomms6070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190664PMC
October 2014

Begin at the beginning: A BAC-end view of the passion fruit (Passiflora) genome.

BMC Genomics 2014 Sep 26;15:816. Epub 2014 Sep 26.

Departamento de Genética, Universidade de São Paulo, Escola Superior de Agricultura "Luiz de Queiroz", P,O, Box 83, 13400-970 Piracicaba, Brazil.

Background: The passion fruit (Passiflora edulis) is a tropical crop of economic importance both for juice production and consumption as fresh fruit. The juice is also used in concentrate blends that are consumed worldwide. However, very little is known about the genome of the species. Therefore, improving our understanding of passion fruit genomics is essential and to some degree a pre-requisite if its genetic resources are to be used more efficiently. In this study, we have constructed a large-insert BAC library and provided the first view on the structure and content of the passion fruit genome, using BAC-end sequence (BES) data as a major resource.

Results: The library consisted of 82,944 clones and its levels of organellar DNA were very low. The library represents six haploid genome equivalents, and the average insert size was 108 kb. To check its utility for gene isolation, successful macroarray screening experiments were carried out with probes complementary to eight Passiflora gene sequences available in public databases. BACs harbouring those genes were used in fluorescent in situ hybridizations and unique signals were detected for four BACs in three chromosomes (n=9). Then, we explored 10,000 BES and we identified reads likely to contain repetitive mobile elements (19.6% of all BES), simple sequence repeats and putative proteins, and to estimate the GC content (~42%) of the reads. Around 9.6% of all BES were found to have high levels of similarity to plant genes and ontological terms were assigned to more than half of the sequences analysed (940). The vast majority of the top-hits made by our sequences were to Populus trichocarpa (24.8% of the total occurrences), Theobroma cacao (21.6%), Ricinus communis (14.3%), Vitis vinifera (6.5%) and Prunus persica (3.8%).

Conclusions: We generated the first large-insert library for a member of Passifloraceae. This BAC library provides a new resource for genetic and genomic studies, as well as it represents a valuable tool for future whole genome study. Remarkably, a number of BAC-end pair sequences could be mapped to intervals of the sequenced Arabidopsis thaliana, V. vinifera and P. trichocarpa chromosomes, and putative collinear microsyntenic regions were identified.
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http://dx.doi.org/10.1186/1471-2164-15-816DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4189760PMC
September 2014
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