Heterochromatin Bands and rDNA Sites Evolution in Polyploidization Events in Cynodon Rich. (Poaceae)

Chiavegatto, Raquel Bezerra; Chaves, Ana Luisa Arantes; Rocha, Laiane Corsini; Benites, Flávio Rodrigo Gandolfi; Peruzzi, Lorenzo; Techio, Vânia Helena

doi:10.1007/s11105-019-01173-2

Cited by 7 publications

(6 citation statements)

References 42 publications

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“…Data analysis of D. abyssinica genotypes compared to the cytogenetic study performed in C. dactylon by Chiavegatto (2016,2019) revealed differences in chromosome size, karyotypical symmetry, and the position ribosomal DNA sites. In Digitaria abyssinica, the 35S/CMA + rDNA sites were located at terminal positions in chromosome groups 2 and 5, while in C. dactylon, the position was (peri)centromeric in pairs 2 and 2′ (Chiavegatto et al 2019). On the other hand, the 5S rDNA sites were located at the proximal position in group 7 in D. abyssinica and at the terminal position in pair 5′ in C. dactylon (Chiavegatto et al 2019).…”

Section: Discussionmentioning

confidence: 96%

“…In Digitaria abyssinica, the 35S/CMA + rDNA sites were located at terminal positions in chromosome groups 2 and 5, while in C. dactylon, the position was (peri)centromeric in pairs 2 and 2′ (Chiavegatto et al 2019). On the other hand, the 5S rDNA sites were located at the proximal position in group 7 in D. abyssinica and at the terminal position in pair 5′ in C. dactylon (Chiavegatto et al 2019).…”

Section: Discussionmentioning

confidence: 96%

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Karyotype and leaf epidermis histology traits of Digitaria abyssinica (Hochst. Ex A. Rich.) (Poaceae)

et al. 2020

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Digitaria abyssinica (African couchgrass) has economic potential as forage. This species is taxonomically complex, with a high number of synonyms, basic chromosome number x = 9, and diploid and tetraploid cytotypes. Anatomical, histological, and cytotaxonomic studies may contribute to the taxonomic description of this species and reveal its polyploidization and hybridization events. To this end, this study aimed to characterize the karyotype and leaf epidermis histology of two D. abyssinica genotypes. Chromosome characterization was performed based on chromosome banding using chromomycin A (CMA) and 4,6diamidino-2-phenylindole (DAPI) and identification of 35S and 5S rDNA sites by fluorescent in situ hybridization. Nuclear DNA quantification was performed by flow cytometry. Paradermal sections were obtained for the leaf epidermis study by light and electron microscopy. The results confirmed that both genotypes are tetraploid (2n = 36). The number and distribution of 35S and 5S rDNA sites suggest the occurrence of postpolyploidization structural chromosomal changes or hybridization processes. Despite intraspecific variation in the number of 5S rDNA sites and CMA + /DAPI + bands, no changes were identified in karyotypical symmetry or genome size. Leaf epidermis histology traits and cytogenetic data can support breeding programs and germplasm banks in identifying species or cultivars.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 96%

Karyotype and leaf epidermis histology traits of Digitaria abyssinica (Hochst. Ex A. Rich.) (Poaceae)

et al. 2020

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“…This recurring inconsistency in the number of 45S rDNA sites detected indicates high genome instability in these distinct lineages distributed to both groups. One possibility is that 45S rDNA tandem repeats were lost or reduced in size in cyt-B3 and cyt-B7 in both IpaDur1 and IpaDur2; another is the remodeling of chromatin ( Liu and Wendel 2003 ; Neves et al 2005 ; Chiavegatto et al 2019 ) that altered probe hybridization or fluorescence detection (also see Gao et al 2021 ). These chromosomal changes are consistent with those observed in other recently formed allotetraploids ( Xiong et al 2011 ; Chester et al 2015 ) but contrasts very strongly to the higher cytogenetic stability generally observed in polyploid crops, including the natural allotetraploids, A. hypogaea and A. monticola ( Nascimento et al 2018 ; Bertioli et al 2019 ).…”

Section: Discussionmentioning

confidence: 99%

Spontaneous generation of diversity inArachisneopolyploids (Arachis ipaënsis×Arachis duranensis)4x replays the early stages of peanut evolution

Leal‐Bertioli

Nascimento

Chavarro³

et al. 2021

G3 Genes|Genomes|Genetics

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Polyploidy is considered a driving force in plant evolution and domestication. Although in the genus Arachis, several diploid species were traditionally cultivated for their seeds, only the allotetraploid peanut Arachis hypogaea became the successful, widely spread legume crop. This suggests that polyploidy has given selective advantage for domestication of peanut. Here we study induced allotetraploid (neopolyploid) lineages obtained from crosses between the peanut’s progenitor species, A. ipaënsis and A. duranensis, at earlier and later generations. We observed plant morphology, seed dimensions, and genome structure using cytogenetics (FISH and GISH) and SNP genotyping. The neopolyploid lineages show more variable fertility and seed morphology than their progenitors and cultivated peanut. They also showed sexual and somatic genome instability, evidenced by changes of number of detectable 45S rDNA sites, and extensive homoeologous recombination indicated by mosaic patterns of chromosomes and changes in dosage of SNP alleles derived from the diploid species. Genome instability was not randomly distributed across the genome: the more syntenic chromosomes, the higher homoeologous recombination. Instability levels are higher than observed on peanut lines, therefore it is likely that more unstable lines tend to perish. We conclude that early stages of the origin and domestication of the allotetraploid peanut involved two genetic bottlenecks: the first, common to most allotetraploids, is composed of the rare hybridization and polyploidization events, followed by sexual reproductive isolation from its wild diploid relatives. Here we suggest a second bottleneck: the survival of the only very few lineages that had stronger mechanisms for limiting genomic instability.

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“…Interestingly, three hemizygous loci were detected: seven loci and three loci of 45S rDNA in H. stelligerum and H. umbellatum, and three loci of 5S rDNA in H. sparsum. Hemizygous rDNA loci were also observed in other plant groups, for example in diploid and polyploid grasses (Rocha et al, 2018;Chiavegatto et al, 2019) and diploid orchids (Lan and Albert, 2011). Generally, a potential reason for the observation of hemizygous loci is hybridization (Myburg et al, 2003).…”

Section: Organization Of 45s and 5s Rdnamentioning

confidence: 96%

Molecular Evolution and Organization of Ribosomal DNA in the Hawkweed Tribe Hieraciinae (Cichorieae, Asteraceae)

et al. 2021

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Molecular evolution of ribosomal DNA can be highly dynamic. Hundreds to thousands of copies in the genome are subject to concerted evolution, which homogenizes sequence variants to different degrees. If well homogenized, sequences are suitable for phylogeny reconstruction; if not, sequence polymorphism has to be handled appropriately. Here we investigate non-coding rDNA sequences (ITS/ETS, 5S-NTS) along with the chromosomal organization of their respective loci (45S and 5S rDNA) in diploids of the Hieraciinae. The subtribe consists of genera Hieracium, Pilosella, Andryala, and Hispidella and has a complex evolutionary history characterized by ancient intergeneric hybridization, allele sharing among species, and incomplete lineage sorting. Direct or cloned Sanger sequences and phased alleles derived from Illumina genome sequencing were subjected to phylogenetic analyses. Patterns of homogenization and tree topologies based on the three regions were compared. In contrast to most other plant groups, 5S-NTS sequences were generally better homogenized than ITS and ETS sequences. A novel case of ancient intergeneric hybridization between Hispidella and Hieracium was inferred, and some further incongruences between the trees were found, suggesting independent evolution of these regions. In some species, homogenization of ITS/ETS and 5S-NTS sequences proceeded in different directions although the 5S rDNA locus always occurred on the same chromosome with one 45S rDNA locus. The ancestral rDNA organization in the Hieraciinae comprised 4 loci of 45S rDNA in terminal positions and 2 loci of 5S rDNA in interstitial positions per diploid genome. In Hieracium, some deviations from this general pattern were found (3, 6, or 7 loci of 45S rDNA; three loci of 5S rDNA). Some of these deviations concerned intraspecific variation, and most of them occurred at the tips of the tree or independently in different lineages. This indicates that the organization of rDNA loci is more dynamic than the evolution of sequences contained in them and that locus number is therefore largely unsuitable to inform about species relationships in Hieracium. No consistent differences in the degree of sequence homogenization and the number of 45S rDNA loci were found, suggesting interlocus concerted evolution.

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Heterochromatin Bands and rDNA Sites Evolution in Polyploidization Events in Cynodon Rich. (Poaceae)

Cited by 7 publications

References 42 publications

Karyotype and leaf epidermis histology traits of Digitaria abyssinica (Hochst. Ex A. Rich.) (Poaceae)

Karyotype and leaf epidermis histology traits of Digitaria abyssinica (Hochst. Ex A. Rich.) (Poaceae)

Spontaneous generation of diversity inArachisneopolyploids (Arachis ipaënsis×Arachis duranensis)4x replays the early stages of peanut evolution

Molecular Evolution and Organization of Ribosomal DNA in the Hawkweed Tribe Hieraciinae (Cichorieae, Asteraceae)

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