A. Morielle-Souza and M.T.V. Azeredo-Oliveira
Published September 30, 2007
Genet. Mol. Res. 6 (3): 713-720 (2007)

About the authors
A. Morielle-Souza and M.T.V. Azeredo-Oliveira

Corresponding author
M.T.V. Azeredo-Oliveira
E-mail: tercilia@ibilce.unesp.br

ABSTRACT

A comparative study of holocentric chromosomes in the triatomine species Panstrongylus megistus, Rhodnius pallescens and Triatoma infestans was carried out in order to characterize heterochro- matin, rDNA active sites and nucleolar proteins. Cytological preparations of seminiferous tubules were stained by silver impregnation, C banding, fluorochromes CMA/DA and DAPI/DA, and fluorescent in situ hybrid- ization (FISH) with Drosophila melanogaster 28S rDNA probe. Our results showed interesting aspects of the organization of chromatin and chromosomes in the meiotic cells of these insects. In R. pallescens, sex chromosomes (X, Y) were distinct from autosomes, when submitted to silver impregnation, C banding, CMA, staining, and FISH, confirming that these chromosomes bear nucleolar organizer regions (NORs). In P. megistus, two of the three sex chromosomes were CMA/DAPI; at early meiotic prophase and at diakinesis, silver impregnation corresponded with FISH signals, indicating that in this species, two chromosomes (probably a sex chromosome and an autosome) bear NORs. In T. infestans, silver ni- trate and FISH also stained corresponding areas on meiotic chromosomes. Our data suggest that in triatomines, in general, the number and location of NORs are species-specific. These regions may be considered important chromosome markers for comparative studies to improve the understand- ing of evolutionary mechanisms in these hematophagous insects.

Key words: Holocentric chromosomes, Nucleolus organizer region, CMA, DAPI, Fluorescent in situ hybridization, Triatomines