Spizellomyces punctatus mtDNA
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We have determined the complete sequence
of the 61.3 kbp long mtDNA of the chytridiomycete fungus, Spizellomyces
punctatus (Barr), which is organized in three (one big and two small
1.5 kbp) circular chromosomes. One of the two small circles codes for the
atp9 gene, whereas the other one carries only a conserved promoter-like
element but no identified gene. The set of identified genes is typical
for fungal mitochondria, and contain several group I introns (three in
cob, two in cox1, one in cox3 and two in nad5. The number of identified
tRNA genes (eight) is insufficient to read all codons of the mitochondrial
protein genes (as in Harpochytrium and in Rhizophydium),
and the tRNAs have be edited in order to conform to a standard structural
model (as in Harpochytrium). The protein coding genes contain many
in-frame UAG "stop" codons, which are likely translated as leucine.
In fact, one of tRNAs has an anticodon that would specifically recognize
UAG codons, and this tRNA has a striking similarity to leucine tRNAs from
other species (including a long extra arm)
The phylogenetic analysis places Spizellomyces , a member
of the Spizellomycetales, into the same major lineage as Rhizophydium
(Chytridiales) and Rhizophlyctis rosea, but very distant from the
Monoblepharidales. Its closest
phylogenetic neighbor is Rhizophlyctis rosea, a species which
was previously not well classified, in taxonomic terms.
References:
- Laforest M-J, Roewer I and Lang BF (1997).
"Mitochondrial tRNAs in the lower fungus Spizellomyces punctatus:
tRNA editing and UAG 'stop' codons recognized as leucine." Nucleic
Acids Res 25:626-632. Abstract
[ Allomyces
| Aspergillus|
Harpochytrium
| Monoblepharella
| Monosiga
| Phytophtora
| Rhizophydium
| Rhizopus
| Schizophyllum
| Schizosaccharomyces
| Spizellomyces
]