Related Experiment Video
Updated: May 15, 2026

Single Nucleotide Polymorphism-sensitive FISH Detection of Locus-specific Ribosomal RNA Transcription in Drosophila melanogaster
Published on: March 28, 2025
Next generation sequencing analysis reveals a relationship between rDNA unit diversity and locus number in Nicotiana
Roman Matyášek1, Simon Renny-Byfield, Jaroslav Fulneček
1Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i, Královopolská 135, Brno CZ-612 65, Czech Republic.
Background:
Tandemly arranged nuclear ribosomal DNA (rDNA), encoding 18S, 5.8S and 26S ribosomal RNA (rRNA), exhibit concerted evolution, a pattern thought to result from the homogenisation of rDNA arrays. However rDNA homogeneity at the single nucleotide polymorphism (SNP) level has not been detailed in organisms with more than a few hundred copies of the rDNA unit. Here we study rDNA complexity in species with arrays consisting of thousands of units.
Methods:
We examined homogeneity of genic (18S) and non-coding internally transcribed spacer (ITS1) regions of rDNA using Roche 454 and/or Illumina platforms in four angiosperm species, Nicotiana sylvestris, N. tomentosiformis, N. otophora and N. kawakamii. We compared the data with Southern blot hybridisation revealing the structure of intergenic spacer (IGS) sequences and with the number and distribution of rDNA loci.
Results And Conclusions:
In all four species the intragenomic homogeneity of the 18S gene was high; a single ribotype makes up over 90% of the genes. However greater variation was observed in the ITS1 region, particularly in species with two or more rDNA loci, where >55% of rDNA units were a single ribotype, with the second most abundant variant accounted for >18% of units. IGS heterogeneity was high in all species. The increased number of ribotypes in ITS1 compared with 18S sequences may reflect rounds of incomplete homogenisation with strong selection for functional genic regions and relaxed selection on ITS1 variants. The relationship between the number of ITS1 ribotypes and the number of rDNA loci leads us to propose that rDNA evolution and complexity is influenced by locus number and/or amplification of orphaned rDNA units at new chromosomal locations.
More Related Videos
09:32An Array-based Comparative Genomic Hybridization Platform for Efficient Detection of Copy Number Variations in Fast Neutron-induced Medicago truncatula Mutants
Published on: November 8, 2017
09:34Targeted Next-generation Sequencing and Bioinformatics Pipeline to Evaluate Genetic Determinants of Constitutional Disease
Published on: April 4, 2018
Related Concept Videos
Comparing Copy Number Variations and SNPs
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
Dihybrid Crosses
Evolutionary Relationships through Genome Comparisons
Law of Independent Assortment
Single Nucleotide Polymorphisms-SNPs
Next-generation Sequencing
Next-Generation Sequencing Methods
Although all next-generation methods use different technologies, they all share a set of standard features.