Long- and short-term selective forces on malaria parasite genomes

Plasmodium parasites,the causal agents of malaria,result in more than 1 million deaths annually. plasmodium are unicellular eukaryotes with small ~23 mb genomes encoding ~5200 protein-coding genes. the protein-coding genes comprise about half of these genomes. although evolutionary processes have a significant impact on malaria control,the selective pressures within plasmodium genomes are poorly understood,particularly in the non-protein-coding portion of the genome. we use evolutionary methods to describe selective processes in both the coding and non-coding regions of these genomes. based on genome alignments of seven plasmodium species,we show that protein-coding,intergenic and intronic regions are all subject to purifying selection and we identify 670 conserved non-genic elements. we then use genome-wide polymorphism data from p. falciparum to describe short-term selective processes in this species and identify some candidate genes for balancing (diversifying) selection. our analyses suggest that there are many functional elements in the non-genic regions of these genomes and that adaptive evolution has occurred more frequently in the protein-coding regions of the genome. © 2010 nygaard et al.