Identification of enhancer-like elements in the ribosomal intergenic spacer of Odontophrynus americanus 2n and 4n (Amphibia, Anura)

Author: Alvares L.E.   Brison O.   Ruiz I.R.G.  

Publisher: Springer Publishing Company

ISSN: 0016-6707

Source: Genetica, Vol.104, Iss.1, 1998-10, pp. : 41-44

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Abstract

Repetitive elements are found in the ribosomal intergenic spacer (IGS) of most organisms. A particularly complex pattern of internal repetition occurs in the IGSs of O. americanus 2n and 4n, which are composed of several types of BamHI subrepeats (B-SRs). The most repetitive one is approximately 87 bp long, and is highly represented in the IGS variants of these amphibians. Sequence analyses of six diploid and two tetraploid B-SRs show 87% and 86% homology, respectively, and related secondary structure predictions. The comparison of the 2n and 4n B-SR sequences aligned with the 81 bp enhancer of Xenopus laevis reveals 36%homology. Furthermore, other B-SR features like size, number, and secondary structures resemble those of Xenopus enhancers, suggesting that B-SRs may function as regulators of O. americanus rDNA transcription. The present data also corroborate the close evolutionary relationship between 2n and 4n O. americanus species.

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