scholarly journals Comparative analysis of the ribosomal DNA repeat unit (rDNA) of Perna viridis (Linnaeus, 1758) and Perna canaliculus (Gmelin, 1791)

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7644
Author(s):  
Zhansheng Guo ◽  
Leng Han ◽  
Zhenlin Liang ◽  
Xuguang Hou
Keyword(s):  
Ribosomal Dna ◽  
Phylogenetic Trees ◽  
Repeat Unit ◽  
Cpg Islands ◽  
Intergenic Spacer ◽  
Initiation Site ◽  
Perna Viridis ◽  
28S Rrna ◽  
Important Species ◽  
Perna Canaliculus

Perna viridis and P. canaliculus are economically and ecologically important species of shellfish. In this study, the complete ribosomal DNA (rDNA) unit sequences of these species were determined for the first time. The gene order, 18S rRNA–internal transcribed spacer (ITS) 1–5.8S rRNA–ITS2–28S rRNA–intergenic spacer (IGS), was similar to that observed in other eukaryotes. The lengths of the P. viridis and P. canaliculus rDNA sequences ranged from 8,432 to 8,616 bp and from 7,597 to 7,610 bp, respectively, this variability was mainly attributable to the IGS region. The putative transcription termination site and initiation site were confirmed. Perna viridis and P. canaliculus rDNA contained two (length: 93 and 40 bp) and one (length: 131 bp) repeat motifs, respectively. Individual intra-species differences mainly involved the copy number of repeat units. In P. viridis, three cytosine-guanine (CpG) sites with sizes of 440, 1,075 and 537 bp were found to cover nearly the entire IGS sequence, whereas in P. canaliculus, two CpG islands with sizes of 361 and 484 bp were identified. The phylogenetic trees constructed with maximum likelihood and neighbour-joining methods and based on ITS sequences were identical and included three major clusters. Species of the same genus were easily clustered together.

scholarly journals Comparative Analysis of the nrDNA Repeat Unit of Manila Clam Ruditapes philippinarum and Quahog Mercenaria mercenaria

Fishes ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 42
Author(s):  
Zhansheng Guo ◽  
Zhen Wang ◽  
Xuguang Hou
Keyword(s):  
18S Rrna ◽  
Phylogenetic Analyses ◽  
Repeat Unit ◽  
Cpg Islands ◽  
Intergenic Spacer ◽  
Mercenaria Mercenaria ◽  
Ruditapes Philippinarum ◽  
28S Rrna ◽  
Rdna Unit ◽  
Coding Regions

Ruditapes philippinarum and Mercenaria mercenaria are economically important bivalve species. The complete ribosomal DNA (rDNA) unit sequences of R. philippinarum and M. mercenaria, with as-sembled rDNA unit lengths of 12,910 and 12,100 bp, respectively, were obtained in this study for the first time. The rDNA unit structural organisation was similar to that in other eukaryotes, in-cluding the following elements in order: 18S rRNA-internal transcribed spacer 1 (ITS1); 5.8S rRNA-ITS2-28S rRNA-intergenic spacer (IGS) (3′ external transcribed spacer (ETS); non-transcribed spacer (NTS)-5′ ETS). The genetic differences between R. philippinarum and M. mercenaria were mainly attributable to non-coding regions (ITS1, ITS2 and IGS), especially the IGS region. The boundaries of putative 3′ ETS, NTS and 5′ ETS were confirmed. Seven and three sub-repeat fragments were found in R. philippinarum and M. mercenaria, respectively. These frag-ments ranged from 4 to 154 bp in length, and were located at the NTS and 5′ ETS regions. Five and six cytosine–guanine (CpG) islands were detected in R. philippinarum and M. mercenaria, respec-tively, and these covered 85.58% and 79.29% of the entire IGS sequence, respectively. The phylo-genetic tree was constructed based on Veneridae ITS and 18S rRNA sequences using the maxi-mum likelihood (ML) method. The ML tree based on ITS revealed that species within the same genus clearly clustered together with relatively high supporting values, and all the genera were recovered as monophyletic. The phylogenetic analyses using 18S rRNA provided a weaker phy-logenetic signal than ITS.

Polymorphism in ribosomal DNA repeat units of 12 Hordeum species

Genome ◽  
1989 ◽  
Vol 32 (6) ◽  
pp. 1124-1127 ◽  
Author(s):  
Stephen J. Molnar ◽  
George Fedak
Keyword(s):  
Ribosomal Dna ◽  
Repeat Unit ◽  
Unit Length ◽  
Intergenic Spacer ◽  
Rdna Repeat ◽  
Repeat Units ◽  
Dna Repeat ◽  
Rdna Repeat Unit ◽  
Bamhi Restriction Site ◽  
Hordeum Species

Total genomic DNA was isolated from leaves of individual accessions of 12 Hordeum species. SacI, HindIII, and BamHI restriction fragments hybridizing to the wheat rDNA probe pTA71 were compared. Thirteen rDNA repeat unit length variants were recovered, which combined to produce 11 distinct phenotypes. All rDNA repeat units had two SacI sites and no HindIII sites. The rDNA repeat units of H. secalinum, H. hrasdanicum, and H. distichum all had 3 BamHI sites, but in different configurations. The rDNA repeat units of the other species had at least 4 BamHI sites. Ladders of small hybridizing fragments in 8 of 9 of the latter accessions indicated the presence of occasional BamHI sites in some subrepeats within the intergenic spacer regions of the rDNA repeat units. Different distributions of BamHI restriction site maps within the Hordeum sections strengthen the concept of using variation in rDNA restriction sites as a taxonomic character.Key words: Hordeum, ribosomal DNA, polymorphism.

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