Genome-Wide Patterns of Genetic Polymorphism and Signatures of Selection in Plasmodium vivax

zaidan zaky;

Plasmodium vivaxis the most prevalent human malaria parasite out side of Africa. Yet, studies aim ed to identify genes with signatures consistent with natural selection are rare. Here, we present a comparative analysis of the pattern of genetic variation of five sequenced isolates of P.vivaxand its divergence with two closely related species, Plasmodium cynomolgi and Plasmodium know lesi, using a set of orthologousgenes. In contrast to Plasmodium falciparum, the parasite that causes the most let half or mof human malaria, we did not find significant constraints on the evolution of synonymouss it esgenomewidein P.vivax.The comparative analysis of poly morphism and divergence across loci allowed us to identify 87 genes with patterns consistent with positive selection, including genes involvedin the “exportome” of P. vivax, which are potentially involved in evasion of the host immune system. Nevertheless, we have found a pattern of polymorphism genome wide that is consistent with a significant amount of constraint on the replacement changes and prevalent negative selection. Our analyses also show that silent polymorphism tends to be larger toward the ends of the chromosomes, where many genes involved in antigenicity are located, suggesting that natural selection acts not only by shaping the patterns of variation within the genes but it also affects genome organization.