Heterochromatic DNA in Triturus (Amphibia, Urodela) II. A centromeric satellite DNA.

The MspI family of highly repeated sequences is a centromeric satellite DNA representing about 1% of the genome of the Italian smooth newt, Triturus vulgaris meridionalis. We have studied the structure, genomic organization, chromosomal localization and conservation across species of this family. MspI sequences are around 197 bp long, as shown by sequencing of three cloned units. The family is organized in large clusters of tandemly arrayed units, present at almost all the centromeres of T.v. meridionalis, and is well conserved in the T.v. vulgaris subspecies. Conserved MspI sequences are also present in the related species T. helveticus, where they appear to be clustered at the centromeres of only a few chromosomes. MspI sequences are not found in other Triturus species analysed. The correlation of these sequences with the overall distribution pattern of heterochromatin and the extent of their conservation within the genus Triturus, are discussed.