Abstract
BackgroundThe analysis of the chromosomal and genome evolution in organisms with holocentric chromosomes is restricted by the lack of primary constriction or centromere. An interesting group is the hemipteran subfamily Triatominae, vectors of Chagas disease, which affects around 6 to 7 million people worldwide. This group exhibits extensive variability in the number and chromosomal location of repeated sequences such as heterochromatin and ribosomal genes. This paper tries to reveal the significant differences of the repeated sequences among Triatoma species through the use of genomic DNA probes.MethodsWe analysed the chromosomal distribution and evolution of repeated sequences in Triatoma species by genomic in situ hybridization (GISH) using genomic DNA probes from two North American Triatoma species. These genomic probes were hybridized both on their own chromosomes and on other Triatoma species from North and South America, with different amounts and chromosome location of C-heterochromatin. The results were compared with those previously described using South American Triatoma genomic probes.ResultsWe observed two chromosomal hybridization patterns: (i) very intense hybridization signals concentrated on specific chromosomal regions or particular chromosomes; and (ii) lower intensity hybridization signals dispersed along all chromosomes. Self-GISH on T. rubrofasciata and T. dimidiata chromosomes presented strong hybridization signals on all C-heterochromatin regions. However, when we perform genomic cross-hybridizations, only strong signals are detected on the Y chromosome, leaving the C-heterochromatic autosomal regions unmarked.ConclusionsWe confirm that repeated DNA of the Y chromosome is shared among Triatoma species and probably represents an ancestral character of the Triatomini tribe. On the contrary, autosomal heterochromatic regions are constituted by species-specific DNA repeats, most probably satDNA families, suggesting that Triatoma speciation involved the amplification of diverse types of autosomal repeats. Molecular characterization of principal repetitive DNAs seems to be an appropriate approach to infer evolutionary relationships in triatomines.
Highlights
The analysis of the chromosomal and genome evolution in organisms with holocentric chromosomes is restricted by the lack of primary constriction or centromere
Genomic DNA probes were made from two Triatoma species of the rubrofasciata group: T. rubrofasciata collected in Vietnam
Triatoma rubrofasciata gDNA probe Self-genomic in situ hybridization (GISH) results on T. rubrofasciata showed that almost all chromatin presented scattered hybridization signals
Summary
The analysis of the chromosomal and genome evolution in organisms with holocentric chromosomes is restricted by the lack of primary constriction or centromere. In the Hemiptera, the reduviid subfamily Triatominae comprises vectors for Chagas disease, an anthropozoonotic illness caused by the protozoan parasite Trypanosoma cruzi, which affects six to seven million people worldwide, mostly in Latin America but is increasingly detected in USA, Canada, and many European countries [9] In this hemipteran group, the lack of primary constriction and their small chromosome size greatly hamper chromosome studies. Unlike other insects or even other hemipteran families such as Coreidae or Pentatomidae, FISH analyses using other multigene families’ probes such as 5S rDNA, U2 snDNA or histone genes, failed to achieve satisfactory results in this insect group In this way, different methodological approaches were applied to analyse repetitive sequences of triatomines such as genomic in situ hybridization (GISH) [16] and chromosomal microdissection [17]. These DNA probes were hybridized both on their own chromosomes (self-GISH) and on other Triatoma species, with different amount and chromosomal location of the C-heterochromatin
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