Ribosomal RNA Genes of the Anopheles gambiae Species Complex

Collins, Frank H.; Paskewitz, Susan M.; Finnerty, Victoria

doi:10.1007/978-1-4612-3292-6_1

Cited by 40 publications

(28 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…gambiae is located in the heterochromatin close to the centromere of the X chromosome (Collins et al 1989). This heterochromatin is not included in the An.…”

Section: Resultsmentioning

confidence: 99%

Reduced Recombination Rate and Genetic Differentiation Between the M and S Forms ofAnopheles gambiaes.s.

et al. 2006

View full text Add to dashboard Cite

Genetic differentiation between the largely sympatric molecular forms M and S of Anopheles gambiae appears mostly limited to division 6 and part of division 5 of the X chromosome. This region is adjacent to the centromere and includes the rDNA that was used to define these forms. This localized differentiation between populations that experience gene flow strongly suggests that this region contains genes responsible for reproductive isolation. Regions adjacent to centromeres are known to experience less recombination in several species and it has recently been suggested that low recombination rates can facilitate the accumulation and maintenance of isolation genes in partially isolated populations. Therefore, we measured the recombination rate in division 5D/6 directly and estimate that it is at least 16-fold reduced across this region compared to the remainder of the X chromosome. Additionally, sequence data from four loci from field-collected mosquitoes from several West African countries show very strong differentiation between the molecular forms in division 5D/6, whereas none was observed in two loci elsewhere on the X chromosome. Furthermore, genetic variation was substantially lower in division 5D/6 compared to the two reference loci, and the inferred genealogies of the division 5D/6 genes show patterns consistent with selective sweeps. This suggests that the reduced recombination rate has increased the effect of selection on this region and that our data are consistent with the hypothesis that reduced recombination rates can play a role in the accumulation of isolation genes in the face of gene flow.

show abstract

“…gambiae is located in the heterochromatin close to the centromere of the X chromosome (Collins et al 1989). This heterochromatin is not included in the An.…”

Section: Resultsmentioning

confidence: 99%

Reduced Recombination Rate and Genetic Differentiation Between the M and S Forms ofAnopheles gambiaes.s.

et al. 2006

View full text Add to dashboard Cite

show abstract

“…The An. gambiae complex is an exception to this because the rDNA is X-Ylinked in some species but only X-linked in others (Collins et al 1989). Although intraindividual ITS1 length variation occurs in this complex, it is only seen in the X-Y-linked species (Paskewitz et al 1993).…”

Section: Its1 Internal Repeatsmentioning

confidence: 99%

Internal Repetition and Intraindividual Variation in the rDNA ITS1 of the Anopheles punctulatus Group (Diptera: Culicidae): Multiple Units and Rates of Turnover

Bower

Cooper²,

Beebe

2009

J Mol Evol

View full text Add to dashboard Cite

The rapid divergence of repetitive sequences makes them desirable markers for phylogenetic studies of closely related groups, provided that a high level of sequence homogeneity has been maintained within species. Intraspecific polymorphisms are found in an increasing number of studies now, and this highlights the need to determine why these occur. In this study we examined intraindividual variation present in the first ribosomal internal transcribed spacer (ITS1) from a group of cryptic mosquito species. Individuals of the Anopheles punctulatus group contained multiple ITS1 length variants that ranged from 1.2 to 8.0 kb. Nucleotide and copy number variation for several homologous internal repeats is common, yet the intraspecific sequence divergence of cloned PCR isolates is comparable to that of other mosquito species (*0.2-1.5%). Most of the length variation is comprised of a 5 0 -ITS1 repeat that was identified as a duplication of a conserved ITS2 region. Secondary structure conservation for this repeat is pronounced and several repeat types that are highly homogenized have formed. Significant interspecific divergence indicates a high rate of evolutionary change for this spacer. A maximum likelihood tree constructed here was congruent with previous phylogenetic hypotheses and suggests that concerted evolution is also accompanied by interpopulation divergence. The lack of interindividual differences and the presence of homogenized internal repeats suggest that a high rate of turnover has reduced the overall level of variation. However, the intraindividual variation also appears to be maintained by the absence of a single turnover rate and the complex dynamics of ongoing recombination within the spacer.

show abstract

“…RT1-RT2 and Ri insert in opposite orientations in the rDNA, and 9 bp of the RT1-RT2 target site duplication (TATCCCTGT) are identical but reversed in orientation with respect to 9 bp of the target site duplication of Ri. It is important to note that all individuals of A. gambiae tested have another, 5-kb insertion in approximately 15% of the 28S coding sequences, 5' to the RT1-RT2 insertion site (16). These insertions, which do not vary in abundance, may correspond to Ri and/or R2 elements, but no example has been cloned.…”

Section: Resultsmentioning

confidence: 99%

“…3B). The hybridization signal with the RT2 probe was uniform, taking into account the fact that sons, with about half of the signal intensity, have only one X chromosome, to which the rRNA loci map (16 ant element copies, were omitted from the analysis. The results for both blots are given in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Distinct families of site-specific retrotransposons occupy identical positions in the rRNA genes of Anopheles gambiae.

Besansky¹,

Paskewitz²,

Hamm³

et al. 1992

Mol. Cell. Biol.

View full text Add to dashboard Cite

Two distinct site-specific retrotransposon families, named RT1 and RT2, from the sibling mosquito species Anopheles gambiae and A. arabiensis, respectively, were previously identified. Both were shown to occupy identical nucleotide positions in the 28S rRNA gene and to be flanked by identical 17-bp target site duplications. Full-length representatives of each have been isolated from a single species, A. gambiae, and the nucleotide sequences have been analyzed. Beyond insertion specificity, RT1 and RT2 share several structural and sequence features which show them to be members of the LINE-like, or non-long-terminal-repeat retrotransposon, class of reverse transcriptase-encoding mobile elements. These features include two long overlapping open reading frames (ORFs), poly(A) tails, the absence of long terminal repeats, and heterogeneous 5' truncation of most copies. The first ORF of both elements, particularly ORF1 of RT1, is glutamine rich and contains long tracts of polyglutamine reminiscent of the opa repeat. Near the carboxy ends, three cysteinehistidine motifs occur in ORF1 and one occurs in ORF2. In addition, each ORF2 contains a region of sequence similarity to reverse transcriptases and integrases. Alignments of the protein sequences from RT1 and RT2 reveal 36% identity over the length of ORF1 and 60%o identity over the length of ORF2, but the elements cannot be aligned in the 5' and 3' noncoding regions. Unlike that of RT2, the 5' noncoding region of RT1 contains 3.5 copies of a 500-bp subrepeat, followed by a poly(T) tract and two imperfect 55-bp subrepeats, the second spanning the beginning of ORF1. The pattern of distribution of these elements among five sibling species in the A. gambiae complex is nonuniform. RT1 (43), and the absence of LTRs indicates a very different replication strategy that is not well understood. Peptide alignments show that the RT and capsid-like domains of non-LTR retrotransposons are more closely related to one another than to those of other RTencoding mobile elements (23,51,66,68). However, although the coding region may occupy over 80% of the length of a given element, the sequence diversity among characterized non-LTR retrotransposons is high enough to preclude amino acid alignment of any but very short segments.Many non-LTR retrotransposons, such as mammalian Li elements (32) and Ti elements from mosquitoes in the Anopheles gambiae complex (8, 9), are widely dispersed in the host genomic DNA and have no apparent insertion site specificity. However, some elements of this same class exhibit a preference for a particular target site. In three different trypanosomatid protozoa, three distinct elements (CRE1, SLACS, and CZAR) interrupt some portion of the array of spliced leader RNA genes at the same conserved sequence (2). The Drosophila G element occupies a precise site in the intergenic spacers of the rRNA genes (22

show abstract

Ribosomal RNA Genes of the Anopheles gambiae Species Complex

Cited by 40 publications

References 60 publications

Reduced Recombination Rate and Genetic Differentiation Between the M and S Forms ofAnopheles gambiaes.s.

Reduced Recombination Rate and Genetic Differentiation Between the M and S Forms ofAnopheles gambiaes.s.

Internal Repetition and Intraindividual Variation in the rDNA ITS1 of the Anopheles punctulatus Group (Diptera: Culicidae): Multiple Units and Rates of Turnover

Distinct families of site-specific retrotransposons occupy identical positions in the rRNA genes of Anopheles gambiae.

Contact Info

Product

Resources

About