1 research outputs found
Evolutionary conservation of the circadian gene timeout in Metazoa
<i>Timeless </i>(<i>Tim</i>)
is considered to function as an essential circadian clock gene in <i>Drosophila</i>.
Putative homologues of the <i>Drosophila timeless </i>gene have been identified
in both mice and humans. While <i>Drosophila </i>contains two paralogs, <i>timeless
</i>and <i>timeout</i>, acting in clock/light entrainment and chromosome
integrity/photoreception, respectively, mammals contain only one <i>Tim </i>homolog.
In this paper, we study the phylogeny of the <i>timeless</i>/<i>timeout </i>family
in 48 species [including 1 protozoan (<i>Guillardia theta</i>), 1 nematode (<i>Caenorhabditis
elegans</i>), 8 arthropods and 38 chordates], for which whole genome data are
available by using MEGA (Molecular Evolutionary Genetics Analysis).
Phylogenetic Analysis by Maximum Likelihood (PAML) was used to analyze the
selective pressure acting on metazoan <i>timeless</i>/<i>timeout </i>genes. Our
phylogeny clearly separates insect <i>timeless </i>and <i>timeout </i>lineages
and shows that non-insect animal <i>Tim </i>genes are homologs of insect <i>timeout</i>.
In this study, we explored the relatively rapidly evolving <i>timeless </i>lineage
that was apparently lost from most deuterostomes, including chordates, and from
<i>Caenorhabditis elegans</i>. In contrast, we found that the <i>timeout </i>protein,
often confusingly called “<i>timeless</i>” in the vertebrate literature, is
present throughout the available animal genomes. Selection results showed that <i>timeout
</i>is under weaker negative selection than <i>timeless</i>. Finally, our
phylogeny of <i>timeless</i>/<i>timeout </i>showed an evolutionary conservation
of the circadian clock gene <i>timeout </i>in Metazoa. This conservation is in
line with its multifunctionality, being essential for embryonic development and
maintenance of chromosome integrity, among others