Identification of a mitochondrial Hsp70 in Microsporidia:
Evolutionary and cellular implications
Hirt, R.P., Healy B., Embley, T.M.
Dept. Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD,
United Kingdom
Microsporidia are of practical importance as parasites of animals and more recently as a serious problem for immuno-suppressed humans. From an evolutionary perspective they are considered to be important because they are often the first branching taxa in genes trees for eukaryotes. Compatible with this hypothesis is the apparent absence of mitochondria in microsporidia. Like diplomonads and trichomonads microsporidia have been hypothesised to have diverged from the main eukaryotic stock before the mitochondrion endosymbiosis. We have demonstrated the presence of a heat shock protein (Hsp) 70 homologue in the microsporidia Vairimorpha necatrix. The sequence of the Vairimorpha Hsp70 gene contains features typical of published bacterial and organellar Hsp70 sequences, including strongly conserved functional domains. There is apparently no upstream element which could be identified as a putative organellar targeting sequence although a consensus peroxisomal targeting signal (PTS1 - SKL) is present at the carboxyl terminus. Most interestingly, detailed phylogenetic analyses using (among others) maximum likelihood methods clearly indicated that the new sequence is a highly divergent mitochondrial orthologue. The identification of a mitochondrial Hsp70 on the genome of Vairimorpha necatrix refutes the hypothesis that microsporidia are relics of a pre-mitochondrial phase of eukaryote evolution.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Sunday, April 5 |
02:30 pm |