Does the chromosomal position of 35S rDNA sites influence their transcription? A survey on Nothoscordum species (Amaryllidaceae)

The Dilatata group of Paspalum includes species and biotypes native to temperate South America. Among them, five sexual allotetraploids (x = 10) share the same IIJJ genome formula: P. urvillei Steud, P. dasypleurum Kunze ex Desv., P. dilatatum subsp. flavescens Roseng., B.R. Arrill. & Izag., and two biotypes P. dilatatum Vacaria and P. dilatatum Virasoro. Previous studies suggested P. intermedium Munro ex Morong & Britton and P. juergensii Hack. or related species as their putative progenitors and donors of the I and J genome, respectively, and pointed to a narrow genetic base for their maternal origin. It has not yet been established whether the various members of the Dilatata group are the result of a single or of multiple allopolyploid formations. Here, we aimed to study the evolutionary dynamics of rRNA genes after allopolyploidisation in the Dilatata group of Paspalum and shed some light into the genome restructuring of the tetraploid taxa with the same genome formula. We used double target fluorescence in situ hybridisation of 35S and 5S rDNA probes and sequenced the nrDNA internal transcribed spacer (ITS) region. A variable number of loci at the chromosome ends were observed for the 35S rDNA, from 2 to 6, suggesting gain and loss of sites. For the 5S rDNA, only one centromeric pair of signals was observed, indicating a remarkable loss after polyploidisation. All ITS sequences generated were near identical to the one found for P. intermedium. Although sequences showed a directional homogeneisation towards the putative paternal progenitor in all tetraploid species, the observed differences in the number and loss of rDNA sites suggest independent ongoing diploidisation processes in all taxa and genome restructuring following polyploidy.

Download Full-text

Fluorescence in situ hybridization of 35S rDNA sites and karyotype of wild Lilium (Liliaceae) species from China: taxonomic and phylogenetic implications

Genetic Resources and Crop Evolution ◽

10.1007/s10722-020-00936-1 ◽

2020 ◽

Vol 67 (6) ◽

pp. 1601-1617

Author(s):

Yan-Ping Zhou ◽

Zhong-Xuan Wang ◽

Yun-Peng Du ◽

Jie-Wen Li ◽

Heng-bin He ◽

...

Keyword(s):

In Situ Hybridization ◽

Fluorescence In Situ Hybridization ◽

Rdna Sites ◽

Phylogenetic Implications ◽

35S Rdna

Download Full-text

Intraspecific polymorphism of ribosomal DNA loci number and morphology in Brachypodium pinnatum and Brachypodium sylvaticum

Cellular & Molecular Biology Letters ◽

10.2478/s11658-012-0025-4 ◽

2012 ◽

Vol 17 (4) ◽

Cited By ~ 4

Author(s):

Ewa Breda ◽

Elzbieta Wolny ◽

Robert Hasterok

Keyword(s):

5S Rdna ◽

Staining Technique ◽

Rdna Locus ◽

Chromosomal Distribution ◽

Metaphase Chromosomes ◽

Brachypodium Sylvaticum ◽

Rdna Sites ◽

Rdna Loci ◽

35S Rdna ◽

25S Rdna

AbstractThe genus Brachypodium has become the target of extensive cytomolecular studies since one of its representatives, B. distachyon, has been accepted as a model plant for temperate cereals and forage grasses. Recent preliminary studies suggested that intraspecific rDNA polymorphism can occur in at least two members of the genus, B. sylvaticum and B. pinnatum, so the aim of this study was to further analyse this phenomenon. FISH with 25S rDNA and 5S rDNA probes was performed on somatic metaphase chromosomes, supplemented by the silver staining technique which distinguishes transcriptionally active from inactive 18S-5.8S-25S rDNA loci. The number, size and chromosomal distribution of 5S rDNA loci were very constant: two loci were invariably observed in all studied diploid accessions of both species, while four 5S rDNA loci were present in the tetraploid B. pinnatum. In contrast to 5S rDNA loci, those of the 35S rDNA were more variable. Two or three loci were observed in the diploid B. pinnatum and four in tetraploid accessions. In chromosome complements of B. sylvaticum accessions from two to six 35S rDNA sites were detected. Regardless of total rDNA locus number, only two were transcriptionally active in diploid accessions of both species, while two or four were active in the tetraploid B. pinnatum. Additionally, the fluorescent CMA/DAPI banding method was used to identify the relation between rDNA sites and CMA+ bands. It was revealed that the number and chromosomal distribution of CMA+ bands are in congruence only with 35S rDNA loci which gave strong FISH signals.

Download Full-text

Allopolyploid origin and genome differentiation of the parasitic species Cuscuta veatchii (Convolvulaceae) revealed by genomic in situ hybridization

Genome ◽

10.1139/gen-2018-0184 ◽

2019 ◽

Vol 62 (7) ◽

pp. 467-475 ◽

Cited By ~ 3

Author(s):

Amália Ibiapino ◽

Miguel A. García ◽

Maria Eduarda Ferraz ◽

Mihai Costea ◽

Saša Stefanović ◽

...

Keyword(s):

In Situ Hybridization ◽

Molecular Data ◽

High Rate ◽

Hybrid Origin ◽

Dapi Staining ◽

Rdna Sites ◽

35S Rdna ◽

Genomic Probes ◽

Haploid Karyotype

Interspecific hybridization and genome duplication to form allopolyploids are major evolutionary events in angiosperms. In the parasitic genus Cuscuta (Convolvulaceae), molecular data suggested the existence of species of hybrid origin. One of them, C. veatchii, has been proposed as a hybrid between C. denticulata and C. nevadensis, both included in sect. Denticulatae. To test this hypothesis, a cytogenetic analysis was performed with CMA/DAPI staining and fluorescent in situ hybridization using 5S and 35S rDNA and genomic probes. Chromosomes of C. denticulata were small with a well-defined centromeric region, whereas C. nevadensis had larger, densely stained chromosomes, and less CMA+ heterochromatic bands. Cuscuta veatchii had 2n = 60 chromosomes, about 30 of them similar to those of C. denticulata and the remaining to C. nevadensis. GISH analysis confirmed the presence of both subgenomes in the allotetraploid C. veatchii. However, the number of rDNA sites and the haploid karyotype length in C. veatchii were not additive. The diploid parentals had already diverged in their chromosomes structure, whereas the reduction in the number of rDNA sites more probably occurred after hybridization. As phylogenetic data suggested a recent divergence of the progenitors, these species should have a high rate of karyotype evolution.

Download Full-text

Cytogenetic Analysis and Chromosomal Mapping of Repetitive DNA in Melipona Species (Hymenoptera, Meliponini)

Cytogenetic and Genome Research ◽

10.1159/000501754 ◽

2019 ◽

Vol 158 (4) ◽

pp. 213-224 ◽

Cited By ~ 5

Author(s):

Natália M. Travenzoli ◽

Bárbara A. Lima ◽

Danon C. Cardoso ◽

Jorge A. Dergam ◽

Tânia M. Fernandes-Salomão ◽

...

Keyword(s):

Stingless Bees ◽

Chromosome Evolution ◽

Repetitive Sequences ◽

Sensu Stricto ◽

Chromosomal Mapping ◽

Evolutionary Constraints ◽

Rdna Sites ◽

Melipona Species ◽

The Relationship ◽

Evolutionary Lineages

Stingless bees of the genus Melipona are subdivided into 4 subgenera called Eomelipona, Melikerria, Melipona sensu stricto, and Michmelia according to species morphology. Cytogenetically, the species of the genus Melipona show variation in the amount and distribution of heterochromatin along their chromosomes and can be separated into 2 groups: the first with low content of heterochromatin and the second with high content of heterochromatin. These heterochromatin patterns and the number of chromosomes are characteristics exclusive to Melipona karyotypes that distinguish them from the other genera of the Meliponini. To better understand the karyotype organization in Melipona and the relationship among the subgenera, we mapped repetitive sequences and analyzed previously reported cytogenetic data with the aim to identify cytogenetic markers to be used for investigating the phylogenetic relationships and chromosome evolution in the genus. In general, Melipona species have 2n = 18 chromosomes, and the species of each subgenus share the same characteristics in relation to heterochromatin regions, DAPI/CMA3 fluorophores, and the number and distribution of 18S rDNA sites. Microsatellites were observed only in euchromatin regions, whereas the (TTAGG)6 repeats were found at telomeric sites in both groups. Our data indicate that in addition to the chromosome number, the karyotypes in Melipona could be separated into 2 groups that are characterized by conserved cytogenetic features and patterns that generally are shared by species within each subgenus, which may reflect evolutionary constraints. Our results agree with the morphological separation of the Melipona into 4 subgenera, suggesting that they must be independent evolutionary lineages.

Download Full-text

Conserved Organisation of 45S rDNA Sites and rDNA Gene Copy Number among Major Clades of Early Land Plants

PLoS ONE ◽

10.1371/journal.pone.0162544 ◽

2016 ◽

Vol 11 (9) ◽

pp. e0162544 ◽

Cited By ~ 16

Author(s):

Marcela Rosato ◽

Aleš Kovařík ◽

Ricardo Garilleti ◽

Josep A. Rosselló

Keyword(s):

Copy Number ◽

Gene Copy Number ◽

Land Plants ◽

Gene Copy ◽

45S Rdna ◽

Rdna Gene ◽

Rdna Sites ◽

Early Land

Download Full-text

Comparative Karyotype Investigations in the European Crayfish Astacus astacus and A. leptodactylus (Decapoda, Astacidae)

Crustaceana ◽

10.1163/156854011x607015 ◽

2011 ◽

Vol 84 (12-13) ◽

pp. 1497-1510 ◽

Cited By ~ 7

Author(s):

M. Pavlica ◽

M. Mcžić ◽

G. Klobučar ◽

M. Šrut ◽

I. Maguire ◽

...

Keyword(s):

Chromosome Number ◽

Chromosome Complement ◽

Size Difference ◽

45S Rdna ◽

Astacus Astacus ◽

Fluorochrome Staining ◽

Rdna Sites ◽

Freshwater Habitats ◽

Acrocentric Chromosomes

AbstractThis study reports on the chromosome number and karyological characteristics of the endangered species of European crayfish, Astacus astacus and A. leptodactylus (Decapoda, Astacidae), both native to Croatian freshwater habitats. The karyotype of A. astacus and A. leptodactylus consists of 2n = 176 and 2n = 180 chromosomes, respectively. The haploid chromosome complement of A. astacus consists of 52 metacentric, 35 metacentric-submetacentric, and 1 acrocentric chromosomes. Fluorochrome staining with 4,6-diamino-2-phenylindole (DAPI) has revealed that the karyotypes of A. astacus and A. leptodactylus are characterized by large heterochromatic blocks located at centromeric and intercalary positions on the chromosomes. Interstitial heterochromatic blocks were more frequent in A. astacus than in A. leptodactylus. In both species pairing of chromosomes in meiosis was regular with the majority of bivalents in a ring- and a dumbbell-form. Fluorescence in situ hybridization (FISH) has revealed that two 45S rDNA loci were present in the investigated species. In A. astacus one of the two 45S rDNA-bearing chromosome pairs was highly heteromorphic, exhibiting a three-fold size difference between 45S rDNA sites on homologous chromosomes. Such a size difference was significantly less pronounced in A. leptodactylus. The karyotype differences between A. astacus and A. leptodactylus suggest changes in chromosome number as well as position of repetitive DNAs have played a role in the karyotype evolution of the species of Astacus.

Download Full-text