title: Molecular genetics and comparative genomics reveal RNAi is not functional in malaria parasites.
abstract: Techniques for targeted genetic disruption in Plasmodium, the causative agent of malaria, are currently intractable for those genes that are essential for blood stage development. The ability to use RNA interference (RNAi) to silence gene expression would provide a powerful means to gain valuable insight into the pathogenic blood stages but its functionality in Plasmodium remains controversial. Here we have used various RNA-based gene silencing approaches to test the utility of RNAi in malaria parasites and have undertaken an extensive comparative genomics search using profile hidden Markov models to clarify whether RNAi machinery exists in malaria. These investigative approaches revealed that Plasmodium lacks the enzymology required for RNAi-based ablation of gene expression and indeed no experimental evidence for RNAi was observed. In its absence, the most likely explanations for previously reported RNAi-mediated knockdown are either the general toxicity of introduced RNA (with global down-regulation of gene expression) or a specific antisense effect mechanistically distinct from RNAi, which will need systematic analysis if it is to be of use as a molecular genetic tool for malaria parasites.
authors.affiliation: The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
authors.forename: Jake
authors.initials: J
authors.lastname: Baum
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Papenfuss
authors.forename: Gunnar R
authors.initials: GR
authors.lastname: Mair
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Janse
authors.forename: Dina
authors.initials: D
authors.lastname: Vlachou
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Waters
authors.forename: Alan F
authors.initials: AF
authors.lastname: Cowman
authors.forename: Brendan S
authors.initials: BS
authors.lastname: Crabb
authors.forename: Tania F
authors.initials: TF
authors.lastname: de Koning-Ward
mesh_terms: D000818:Animals; D017125:Genes, Protozoan; D018503:Genome, Protozoan; D023281:Genomics; D010962:Plasmodium berghei / Q000235:genetics* / Q000378:metabolism; D010963:Plasmodium falciparum / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D016372:RNA, Antisense / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D043244:Ribonuclease III / Q000235:genetics
chemical_list: D016372:RNA, Antisense; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D043244:Ribonuclease III