Even though the most deadly form of malaria for humans, Plasmodium falciparum, has been linked to malaria found in chimpanzees, this group has been fairly isolated on the malarial family treeuntil now. A new phylogenetic analysis from the Sackler Institute for Comparative Genomics at the American Museum of Natural History reveals that malarial parasites found in tree-dwelling rats share a close evolutionary relationship with P. falciparum and Plasmodium reichenowi. The analysis is based on amplification of entire mitochondrial genomes of malarial parasites that use humans, rodents, birds, and lizards as their hosts.
"This is the first time that a relationship has been found between human and rodent malaria," says Susan Perkins, Assistant Curator of Invertebrate Zoology at the Museum. "In all past studies, P. falciparum seemed to not be closely related to anything else but the chimpanzee parasite. But this study places it in a sister group of parasites from rodents."
The maternally inherited mitochondria of Plasmodium are among the smallest known in eukaryotes, containing only three protein-coding genes and a total of only about 6,000 nucleotides (the mitochondrial genomes of human and other animals are about 16,000 bases). The genome is also unusual because of its organization into linear, tandemly repeated DNA. These features allowed Perkins to take the unusual step of amplifying the entire genome in a single piece via polymerase chain reaction (PCR) and then sequence it to reconstruct the whole genome. The analysis that produced the phylogenetic tree was based on the sequences of the three protein-coding genes (a total of about 3,300 DNA characters).
The results place the malarial parasites found in African thicket rats, P. chabaudi, P. berghei,, and P. yoelii,, as a sister group of human and chimpanzee P. falciparum, and P. reichenowi,. This is interesting an
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American Museum of Natural History