Sequence and secondary structure of the rDNA second internal transcribed spacer in the sibling species Culex pipiens L. and Cx. quinquefasciatus Say (Diptera: Culicidae)

Abstract

The primary and secondary structure of the second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA) of two members of the Cx. pipiens complex, Cx. pipiens and Cx, quinquefasciatus, were examined in order to better understand the relationships between these two sibling mosquito species. The length of the sequenced rDNA fragments was 512 bp (Cx. pipiens) and 513 bp (Cx. quinquefasciatus), including the ITS2 regions and flanking 5.8S-28S coding regions. The ITS2 sequences of Cx. pipiens and Cx. quinquefasciatus were 297 and 298 bp in length respectively and showed a 97% identity. In fact, they had identical G+C content (58%) and the only differences observed are six mismatches (three transitions/three transversions), six single-base and one triple-base deletions/ insertions. The observed ITS2 secondary structures of Cx. pipiens and Cx. quinquefasciatus were very similar. Furthermore, the ITS2 sequences of specimens belonging to three populations of Cx. pipiens from Italy and four populations of Cx. quinquefasciatus (three from Africa and one from North America) were analysed in order to detect the presence of potential species-specific diagnostic restriction sites.

Phylogeny of Cryptocercus Species (Blattodea: Cryptocercidae) Inferred from Nuclear Ribosomal DNA

“…In general, there was little (ϳ1-2%) or no variation among individuals collected within a location. Previous studies on ITS2 (e.g., Hillis and Davis, 1986;Hillis and Dixon, 1991;Navajas et al, 1998;Severini et al, 1996;Sang et al, 1995;Wesson et al, 1993) have found that intraspecific variation is lower than interspecific variation. In other cases, for example, anopheline mosquitoes (Fritz et al, 1994) and Nasonia species complex (Campbell et al, 1993), the ITS2 of individuals sampled over much of the species distribution showed relatively low level of sequence divergence.…”

Molecular phylogeny of black flies (Diptera: Simuliidae) from Thailand, using ITS2 rDNA

“…pipiens (58%) and Cx. quinquefasciatus (58%) (Severini et al, 1996), as well as in the dragonfly genus Calopteryx (68%) (Weekers, De Jonckheere & Dumont, 2001).…”

“…pipiens (297 bp) and Cx. quinquefasciatus (298 bp) (Severini et al, 1996). The ITS2 sequence of all black flies had a high AT content (71-83.8%).…”

“…In contrast, the noncoding regions of ITS1 and ITS2 are highly variable and evolve at a faster rate than do the coding regions (Schlo¨tterer et al, 1994). The ITS2 sequence comparisons are popular for distinguishing closely related species (e.g., Porter & Collins, 1991;Paskewitz, Wesson & Collins, 1993;Cornel, Porter & Collins, 1996;Severini et al, 1996;Walton et al, 1999;Hackett et al, 2000), for differentiation of populations (Fritz et al, 1994;Marrelli et al, 1999), for study of divergence within and between species (Tang et al, 1996;, and for reconstruction of evolutionary relationships ( e.g., Wesson, Porter & Collins, 1992;Schlo¨tterer et al, 1994;Cornel, Porter & Collins, 1996;Miller, Crabtree & Savage, 1996;Xu & Qu, 1997;Depaquit et al, 2000;Weekers, De Jonckheere & Dumont, 2001;Oliverio, Cervelli & Mariottini, 2002;Toma et al, 2002;Young & Coleman, 2004).…”

RAPD-PCR based genomic characterization of two populations of Culex quinquefasciatus (Diptera : Culicidae)

“…Comparatively less is known about the species of the genus Culex which also include species of epidemiological significance. For the PCR based enzymatic amplification of mosquito genome, random as well as gene specific primers has been developed for selected nuclear and mitochondrial gene sequences (Severini et al, 1996;Crabtree et al, 1995;Cornel et al 1996;Proft et al, 1999;Manonmani et al, 2001;Singh et al, 2004;and Li and Wilkerson, 2005). In fact, the major impetus for mosquito genome studies came from WHO/UNDP/World Bank (2003) special programme for research and training in tropical diseases.…”