Supersaturation mutagenesis reveals adaptive rewiring of essential genes among malaria parasites.

Abstract

Malaria parasites are highly divergent from model eukaryotes. Large-scale genome engineering methods effective in model organisms are frequently inapplicable, and systematic studies of gene function are few. We generated more than 175,000 transposon insertions in the <i>Plasmodium knowlesi</i> genome, averaging an insertion every 138 base pairs, and used this "supersaturation" mutagenesis to score essentiality for 98% of genes. The density of mutations allowed mapping of putative essential domains within genes, providing a completely new level of genome annotation for any <i>Plasmodium</i> species. Although gene essentiality was largely conserved across <i>P. knowlesi</i>, <i>Plasmodium falciparum</i>, and rodent malaria model <i>Plasmodium berghei</i>, a large number of shared genes are differentially essential, revealing species-specific adaptations. Our results indicated that <i>Plasmodium</i> essential gene evolution was conditionally linked to adaptive rewiring of metabolic networks for different hosts.