Distribution of 5S and 35S rRNA gene sites in 34 Chenopodium species (Amaranthaceae)

Abstract

Studies on Chenopodium chromosomes are scarce and restricted mainly to chromosome number estimation. To extend our knowledge on karyotype structure of the genus, the organization of 5S and 35S rRNA genes in Chenopodium chromosomes was studied. The rDNA sites were predominantly located at chromosomal termini, except in a few species where 5S rDNA sites were interstitial. The majority of the diploid species possessed one pair each of 35S and 5S rDNA sites located on separate chromosomes. Slightly higher diversity in rDNA site number was observed in polyploid accessions. One or two pairs of 35S rDNA sites were observed in tetraploids and hexaploids. Tetraploid species had two, four or six sites and hexaploid species had six or eight sites of 5S rDNA, respectively. These data indicate that, in the evolution of some polyploid species, there has been a tendency to reduce the number of rDNA sites. Additionally, polymorphism in rDNA site number was observed. Possible mechanisms of rDNA locus evolution are discussed. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ••, ••–••.

The taxonomic riddle of Chenopodium album L. complex (Amaranthaceae)

“…The diploid showed two pairs, one major and one minor with 5S rDNA loci and two big and one small site in 4x types, while 6x had three pairs of major and one of minor 5S rDNA loci. The physical mapping of rDNA loci made it possible to identify three to five pairs of homologous chromosomes according to the cytotype [14][15][16].…”

Cytogenetic characterization of the Arabidopsis thaliana natural tetraploid ecotype Warschau stability during in vitro regeneration

“…The number of 35S and 5S rDNA loci that were observed in Wa-1 corresponded with the doubled number of rDNA loci found in diploid ecotypes. Such a situation occurs frequently in allo-and autopolyploid species, although the elimination of 35S and/ or 5S rDNA loci during diploidization is well known (Hasterok et al 2006;Kolano et al 2012).…”

FISH mapping of 35S and 5S rRNA genes inArtemisiasubgenusDracunculus(Asteraceae): changes in number of loci during polyploid evolution and their systematic implications

“…DNA sequences encoding the 35S (18S–5.8S–26S) and 5S ribosomal RNA genes are arranged in tandem repeats on one or several pairs of chromosomes, providing essential information about their genomic organization which is useful for understanding the systematic and evolutionary relationships between groups of related species (e.g. Weiss‐Schneeweiss et al ., ; Rosato, Castro & Rosselló, ; Pellicer et al ., ; Kolano et al ., ), tracing changes in cell lines (Kovarik et al ., ), etc. Previous studies in Artemisia have mostly focused on species of subgenera Artemisia , Seriphidium Besser and Tridentatae , and these have shed light on the mechanisms at the chromosome and whole‐genome levels that have given rise to the extensive diversity in ribosomal DNA (rDNA) organization found in the genus (Torrell et al ., ; Garcia et al ., , ).…”