Differential transcription of ribosomal cistrons denoting nucleolar dominance in hybrids of Drosophila mulleri and Drosophila navojoa (mulleri complex, Repleta group)

Leliane Silva Commar,Carlos Roberto Ceron,Paula Rahal,Hermione E.M.C Bicudo

doi:10.1590/s1415-47572007000600028

Leliane Silva Commar, Carlos Roberto Ceron + Show 2 more

Open Access

https://doi.org/10.1590/s1415-47572007000600028

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Abstract

The fruit flies Drosophila mulleri and Drosophila navojoa are included in the mulleri complex of the mulleri subgroup and Repleta group. Although there is no demonstration that interspecific crosses between them occur in nature, they intercross in the laboratory in both cross directions. Previous data have shown the occurrence of nucleolar dominance in interspecific hybrids of some species in the mulleri complex. We investigated nucleolar dominance in D. mulleri/D. navojoa hybrids using the transcription profiles of the rDNA internal transcribed spacer (ITS-1) region. The results showed that the ribosomal cistrons present in the X chromosome and in the microchromosome of D. navojoa are exclusively or preferentially transcribed in these hybrids depending on the cross direction, denoting the complete or partial nucleolar dominance of this species over D. mulleri.

Highlights

The fruit flies Drosophila mulleri and Drosophila navojoa are included in the mulleri complex of the mulleri subgroup and Repleta group
Each transcription unit is composed of an external transcribed spacer (ETS) leader promoter region, an 18S ribosomal RNA (rRNA) coding region, a noncoding internal transcribed spacer (ITS-1), a 5.8S rRNA coding region, a second noncoding ITS region (ITS-2), a 28S rRNA coding region, and, a nontranscribed intergenic spacer segment (IGS) (Hillis and Dixon, 1991, Polanco et al, 1998)
We used differential transcription of ITS-1 rRNA genes to investigate nucleolar dominance in hybrids between D. mulleri and D. navojoa, D. mulleri belonging to the mulleri cluster of the mulleri complex whereas D. navojoa is included in the mojavensis cluster of the same complex (Vilela, 1983, Wasserman, 1992)

Summary

Introduction

The fruit flies Drosophila mulleri and Drosophila navojoa are included in the mulleri complex of the mulleri subgroup and Repleta group. In hybrids involving Drosophila mulleri and Drosophila arizonae ( a mulleri complex species), cytogenetic data have suggested that the ribosomal cistrons present in the X chromosome and microchromosomes of D. arizonae are dominant over those from D. mulleri (Bicudo and Richardson, 1977; Bicudo, 1981; Oliveira et al, 2006).

Results

Conclusion