A novel Modulator of Ring Stage Translation (MRST) gene alters artemisinin sensitivity in Plasmodium falciparum

The implementation of artemisinin combination therapies (ACTs) has greatly decreased deaths caused by Plasmodium falciparum malaria but increasing ACT resistance in Southeast Asia and Africa could reverse this progress. Parasite population genetic studies have identified numerous genes, SNPs, and transcriptional signatures associated with altered artemisinin activity with SNPs in the Kelch13 (K13) gene being the most well characterized artemisinin resistance marker. However, there is increasing evidence that resistance to artemisinin in P. falciparum is not related only to K13 SNPs, prompting the need to characterize other novel genes that can alter ART responses in P. falciparum. In our previous analyses of P. falciparum piggyBac mutants, several genes of unknown function exhibited increased sensitivity to artemisinin that was similar to a mutant of K13. Further analysis of these genes and their gene coexpression networks indicated that the ART-sensitivity cluster was functionally linked to DNA replication and repair, stress responses, and maintenance of homeostatic nuclear activity. In this study, we have characterized PF3D7_1136600, another member of the ART-sensitivity cluster. Previously annotated as a conserved Plasmodium gene of unknown function, we now propose this gene to be a Modulator of Ring Stage Translation (MRST). Our findings reveal that the mutagenesis of MRST affects gene expression of multiple translation associated pathways during early ring stage of asexual development via putative ribosome assembly and maturation activity, suggesting an essential role of MRST in protein biosynthesis and another novel mechanism of altering the parasite ART drug response.