Repetitive sequences in the ITS1 region of ribosomal DNA in congeneric microphallid species (Trematoda: Digenea)

Abstract

In searching for species-specific DNA sequences of microphallid species (Digenea, Trematoda) we examined the ribosomal internal transcribed spacer regions (ITS) of three closely related species (Levinseniella group) hosted by mud snails (first intermediate host) and marine crustaceans (second intermediate host). In the ITS1 region we found consistent patterns of repeating sequences of 130 bp. Within each main repeat there was a varying number of subrepeats specific for each of the species. All repeats including subrepeats were identified by a similar starting sequence: 5'-CCTGTGG-3'. As this sequence has close resemblance to the chi sequence 5'-GCTGGTGG-3' found in phage lambda we speculate if it serves the same function as a recombination hotspot. Alternatively but less likely, it could be an inactive, mutational relic of a sequence that once served this purpose.

Characterization of the Complete Nuclear Ribosomal DNA Sequences ofParamphistomum cervi

“…The long and short repeats leading to size variation were found across a range of helminthes, including trematodes [32–34], cestodes [35], and nematodes [36], but no length variation was detected in any of the P. cervi samples in the present study.…”

Length variation and repetitive sequences of Internal Transcribed Spacer of ribosomal RNA gene, diagnostics and relationships of populations of potato rot nematode, Ditylenchus destructor Thorne, 1945 (Tylenchida: Anguinidae)

“…Minisatellite internal repeats appear to be characteristic of the evolution of the ITS1 in several groups of organisms. Long and short repeats of ITS1 were found in mosquitoes (Paskewitz et al, 1993;Bower et al, 2009), trematodes (van Herwerden et al, 1999Warberg et al, 2005), ladybird beetles (von der Schulenburg et al, 2001), pinyon pines (Ger-nandt et al, 2001) and in several fungus groups (Platas et al, 2001;den Bakker et al, 2004). Several studies showed that these repeats also formed long, stem-loop secondary structures in ITS1.…”

Characterisation and phylogeny of repeated elements giving rise to exceptional length of ITS2 in several downy mildew genera (Peronosporaceae)

“…Large regions containing repeated elements have been reported from the ITS1 region of ladybird species (Graf von der Schulenburg et al, 2001), trematodes (Warberg et al, 2005), and oomycetes (Voglmayr, 2003). However, these do not exhibit structural similarities to the REs found in the ITS2 of the DMPH.…”