Origin and evolution of homologous repeated sequences in the mitochondrial DNA control region of shrews |
| |
Authors: | Fumagalli L; Taberlet P; Favre L; Hausser J |
| |
Institution: | Institut de Zoologie et d'Ecologie Animale, Universite de Lausanne, Dorigny, Switzerland. |
| |
Abstract: | The complete mitochondrial DNA (mtDNA) control region was amplified and
directly sequenced in two species of shrew, Crocidura russula and Sorex
araneus (Insectivora, Mammalia). The general organization is similar to
that found in other mammals: a central conserved region surrounded by two
more variable domains. However, we have found in shrews the simultaneous
presence of arrays of tandem repeats in potential locations where repeats
tend to occur separately in other mammalian species. These locations
correspond to regions which are associated with a possible interruption of
the replication processes, either at the end of the three-stranded D-loop
structure or toward the end of the heavy-strand replication. In the left
domain the repeated sequences (R1 repeats) are 78 bp long, whereas in the
right domain the repeats are 12 bp long in C. russula and 14 bp long in S.
araneus (R2 repeats). Variation in the copy number of these repeated
sequences results in mtDNA control region length differences. Southern blot
analysis indicates that level of heteroplasmy (more than one mtDNA form
within an individual) differs between species. A comparative study of the
R2 repeats in 12 additional species representing three shrew subfamilies
provides useful indications for the understanding of the origin and the
evolution of these homologous tandemly repeated sequences. An asymmetry in
the distribution of variants within the arrays, as well as the constant
occurrence of shorter repeated sequences flanking only one side of the R2
arrays, could be related to asymmetry in the replication of each strand of
the mtDNA molecule. The pattern of sequence and length variation within and
between species, together with the capability of the arrays to form stable
secondary structures, suggests that the dominant mechanism involved in the
evolution of these arrays in unidirectional replication slippage.
|
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|