Reference "Genetic code and phylogenetic origin of oomycetous mitochondria"

Reference ID

9085

Title

Genetic code and phylogenetic origin of oomycetous mitochondria

Source

Journal of molecular evolution, 1992, vol. 34, pp. 254-258

Authors (2)

Karlovsky-P

Fartmann-B

Abstract

We sequenced the 3'-terminal part of the COX3 gene encoding cytochrome c oxidase
subunit 3 from mitochondria of Phytophthora parasitica (phylum Oomycota, kingdom
Protoctista). Comparison of the sequence with known COX3 genes revealed that UGG
is used as a tryptophan codon in contrast to UGA in the mitochondrial codes of
most organisms other than green plants. A very high AT mutation pressure
operates on the mitochondrial genome of Phytophthora, as revealed by codon usage
and by A+T content of noncoding regions, which seems paradoxical because AT
pressure causes tryptophan codon reassignment from UGG to UGA in mitochondria of
most species. The genetic code and other data suggest that mitochondria of
Oomycota share a direct common ancestor with mitochondria of plants and that
mitochondria of the ancestor of Planta and Oomycota were acquired in a second
endosymbiotic event, which occurred later than the acquisition of mitochondria
by other eukaryotes.