Unusual origin of a nuclear pseudogene in the Italian wall lizard: intergenomic and interspecific transfer of a large section of the mitochondrial genome in the genus Podarcis (Lacertidae).
Two distinct cytochrome b-like sequences were discovered in the genome of Podarcis sicula. One of them represents a nuclear copy of a mitochondrial sequence (numt-sic) differing by 14.3% from the authentic mitochondrial (mt) sequence obtained from the same individual. This numt, however, differs by only 2.7% from the mt sequence found in one population of Podarcis muralis, a related species in which no corresponding numt was detected. The numt-sic sequence extends over at least 7637 bp and is homologous to a section of the mt genome spanning from the tRNA-Lys to the tRNA-Pro gene. Premature mt stop codons were detected in two of the nine protein coding genes of numt-sic. The distribution of substitutions among the three codon positions and the transition/transversion ratio of the numt-sic sequence resemble, with few exceptions, those of functional mt genes, indicating a rather recent transfer to the nucleus. Phylogenetic analyses performed on the data set including P. sicula numt-cytb sequences as well as mt-cytb sequences from the same individuals and mt sequences of various P. muralis populations suggest that numt-sic originated in P. muralis. In a geographic survey, P. sicula populations belonging to different mt lineages, covering most of the distribution area, were screened for the presence of numt-sic and for a 15-bp duplication polymorphism in the numt-nd5 sequence. Our results suggest that numt-sic has spread rapidly through the species range via sexual transmission, thereby being transferred to populations belonging to well-separated mt lineages that diverged 1-3 Mya.
Podnar
Martina
M
Molecular Systematics, 1st Zoological Department, Museum of Natural History Vienna, Burgring 7, A-1010 Vienna, Austria.
Haring
Elisabeth
E
Pinsker
Wilhelm
W
Mayer
Werner
W
D000818:Animals; D002467:Cell Nucleus / Q000235:genetics*; D017523:Croatia; D045303:Cytochromes b / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D019143:Evolution, Molecular; D016678:Genome; D006239:Haplotypes; D007558:Italy; D008116:Lizards / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011544:Pseudogenes / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial; D012343:RNA, Transfer; D045303:Cytochromes b