Abstract
AbstractThe horizontal transfer of DNA between different organisms is a major force shaping the genomes of prokaryotes, but is considered to have a minor role in eukaryotes, with only a handful of known examples, mostly of limited size. The nucleotide databases of Plasmodium genomes were divided into small fragments and compared to human, as well as to other Plasmodium genomes. This computational approach revealed that the Plasmodium vivax genome is interlaced with multiple DNA fragments that were likely acquired via horizontal transfer from humans. Contamination is a major concern in such studies; moreover, it must be determined if the identified homologies might be due to chance. These reservations are supported by the fact that the identified homologous sequences were found to be predominantly within short contigs. Re-sequencing of candidate sites using distinct isolations of P. vivax genomic DNA showed deletions not found in the human genome, and with much greater similarity to the P. vivax than human genome. Moreover, the identified fragments were enriched for mRNA coding sequences and genes that are known to be functionally important for P. vivax, including nitric oxide synthase 1 (neuronal) adaptor and Interleukin-1 family, suggesting a functional role. These results are important for two reasons. First, a directional massive horizontal transfer of genetic material from humans to another eukaryote is shown for the first time. This sheds light on parasite evolution, co-adaptation and immune evasion. Second, the DNA found is enriched for Interleukin-1 family, which is known to be essential for malaria protection. This indicates a functional role and might serve to better understand how Plasmodium vivax and the immune system interact.
Highlights
The transfer of DNA between different organisms, horizontal gene transfer (HGT), has long been recognized as a major force shaping the genomes of prokaryotes
To determine whether HGT from humans played a role in the recent evolution of some Plasmodium species, the genomes of eight Plasmodium genome nucleotide databases were divided into 60 letters long fragments and compared to the human genome using BLASTN (Zhang et al 2000; Morgulis et al 2008)
Five independent lines of evidence suggest that the results shown here do not represent errors in the sequencing and assemble of the P. vivax genome, but genuine HGT events. (i) P. vivax was isolated for sequencing from squirrel monkeys (Saimiri boliviensis boliviensis)
Summary
The transfer of DNA between different organisms, horizontal gene transfer (HGT), has long been recognized as a major force shaping the genomes of prokaryotes. HGT have been reported only in a few incidences and on a limited scale These include transfer to Rotifera from multiple sources, bacteria to fungal events, passage of transposons between parasitic bugs and there vertebrate host, the acquisition of carotenoid biosynthesis enzymes by aphids from fungus (Gilbert et al.; Moran et al.; Hall et al 2005a; Gladyshev et al 2008), and some controversial human to Plasmodium HGT events (Deitsch et al 2001a; Deitsch et al 2001b; Striepen et al 2002; Striepen et al 2004; Templeton et al 2004). It is shown that cross-kingdom HGT from humans is likely to have had a significant, and probably functional, contribution to the P. vivax genome
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