Nuclear rDNA pseudogenes in Chagas disease vectors: evolutionary implications of a new 5.8S+ITS-2 paralogous sequence marker in triatomines of North, Central and northern South America.
A pseudogene, paralogous to rDNA 5.8S and ITS-2, is described in Meccus dimidiata dimidiata, M. d. capitata, M. d. maculippenis, M. d. hegneri, M. sp. aff. dimidiata, M. p. phyllosoma, M. p. longipennis, M. p. pallidipennis, M. p. picturata, M. p. mazzottii, Triatoma mexicana, Triatoma nitida and Triatoma sanguisuga, covering North America, Central America and northern South America. Such a nuclear rDNA pseudogene is very rare. In the 5.8S gene, criteria for pseudogene identification included length variability, lower GC content, mutations regarding the functional uniform sequence, and relatively high base substitutions in evolutionary conserved sites. At ITS-2 level, criteria were the shorter sequence and large proportion of insertions and deletions (indels). Pseudogenic 5.8S and ITS-2 secondary structures were different from the functional foldings, different one another, showing less negative values for minimum free energy (mfe) and centroid predictions, and lower fit between mfe, partition function, and centroid structures. A complete characterization indicated a processed pseudogenic unit of the ghost type, escaping from rDNA concerted evolution and with functionality subject to constraints instead of evolving free by neutral drift. Despite a high indel number, low mutation number and an evolutionary rate similar to the functional ITS-2, that pseudogene distinguishes different taxa and furnishes coherent phylogenetic topologies with resolution similar to the functional ITS-2. The discovery of a pseudogene in many phylogenetically related species is unique in animals and allowed for an estimation of its palaeobiogeographical origin based on molecular clock data, inheritance pathways, evolutionary rate and pattern, and geographical spread. Additional to the technical risk to be considered henceforth, this relict pseudogene, designated as "ps(5.8S+ITS-2)", proves to be a valuable marker for specimen classification, phylogenetic analyses, and systematic/taxonomic studies. It opens a new research field, Chagas disease epidemiology and control included, given its potential relationships with triatomine fitness, behaviour and adaptability.
Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain. Electronic address: M.D.Bargues@uv.es.
M Dolores
MD
Bargues
Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain.
M Angeles
MA
Zuriaga
Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain.
Santiago
S
Mas-Coma
D000569:Americas; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D014355:Chagas Disease / Q000635:transmission*; D004275:DNA, Ribosomal / Q000235:genetics*; D019143:Evolution, Molecular; D017344:Genes, Insect; D007303:Insect Vectors / Q000145:classification / Q000235:genetics / Q000469:parasitology; D008969:Molecular Sequence Data; D010802:Phylogeny; D058974:Phylogeography; D011544:Pseudogenes; D014225:Triatominae / Q000145:classification* / Q000235:genetics* / Q000469:parasitology
D004275:DNA, Ribosomal
Chagas disease; Fundamental and applied characterization; New marker; Nuclear rDNA; Pseudogenic 5.8S and ITS-2 sequences; Triatomine vectors