Characterization of two repetitive DNA families (RrS1 and Rana/Pol III) in the genomes of Palaearctic green water frogs

Abstract

Two repetitive DNA families were detected in the genomes of Palaearctic green water frogs. The first family, named RrS1, is a centromeric satellite DNA, which allows discrimination between the genomes of Rana ridibunda and Rana lessonae, thence representing a useful molecular tool to determine timing and modes of genome exclusion from the germ line cells of the hybrid R. es‐culenta. The second repetitive family, named Rana/Pol III, consists of short, tandemly arrayed sequences, scattered throughout the genomes, and resembling SINE retroposons in their structure. The Rana/Pol III family is present in the genomes of R. lessonae, R. ridibunda, and their hybrid R. esculenta, as well as in R. shqiperica, R. epeirotica, R. cretensis, and the Italian taxon. These sequences are also present in the Iberian species R. perezi, although less abundant, but appear to be lacking in the North African species R. saharica. The distribution of Rana/Pol III elements in the genomes of Palaearctic green water frogs is in agreement with the phyletic history of these anurans, on the basis of genetic data, and enables us to suppose that the hybridogenetic mechanism is one of the factors accounting for the possible horizontal transfer of transposable elements.

Key words:

• Repetitive DNAs
• Genome evolution
• Hybrido‐genesis
• Rana esculenta complex.