Retention and loss of RNA interference pathways in trypanosomatid protozoans

• Published in: PLoS pathogens Vol. 6; no. 10; p. e1001161
• Main Authors: Lye, Lon-Fye, Owens, Katherine, Shi, Huafang, Murta, Silvane M F, Vieira, Ana Carolina, Turco, Salvatore J, Tschudi, Christian, Ullu, Elisabetta, Beverley, Stephen M
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01-10-2010; Public Library of Science (PLoS)
• Subjects: Crithidia; Drug resistance; Evolution, Molecular; Gene amplification; Gene expression; Genes, Protozoan; Genetic aspects; Genetic engineering; Genetic Speciation; Genetics and Genomics/Functional Genomics; Genomes; Genomic Instability - genetics; Genomic Instability - physiology; Infectious Diseases; Infectious Diseases/Neglected Tropical Diseases; Infectious Diseases/Protozoal Infections; Leishmania; Leishmania braziliensis; Leishmania braziliensis - genetics; Leishmania braziliensis - metabolism; Leishmania major; Parasites; Phenotype; Phylogeny; Physiological aspects; Proteins; Retention; Ribonucleic acid; RNA; RNA Interference - physiology; RNA, Small Interfering - pharmacology; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Signal Transduction - genetics; Transfection; Trypanosoma cruzi; Trypanosomatina - genetics; Trypanosomatina - immunology; Viannia; Viruses - genetics; United States; Leishmania braziliensis; Genomic Instability; Signal Transduction; Genes, Protozoan; Viruses; Phylogeny; RNA-Binding Proteins; Phenotype; RNA Interference; Genetic Speciation; Trypanosomatina; RNA, Small Interfering; Evolution, Molecular
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1001161

RNA interference (RNAi) pathways are widespread in metaozoans but the genes required show variable occurrence or activity in eukaryotic microbes, including many pathogens. While some Leishmania lack RNAi activity and Argonaute or Dicer genes, we show that Leishmania braziliensis and other species within the Leishmania subgenus Viannia elaborate active RNAi machinery. Strong attenuation of expression from a variety of reporter and endogenous genes was seen. As expected, RNAi knockdowns of the sole Argonaute gene implicated this protein in RNAi. The potential for functional genetics was established by testing RNAi knockdown lines lacking the paraflagellar rod, a key component of the parasite flagellum. This sets the stage for the systematic manipulation of gene expression through RNAi in these predominantly diploid asexual organisms, and may also allow selective RNAi-based chemotherapy. Functional evolutionary surveys of RNAi genes established that RNAi activity was lost after the separation of the Leishmania subgenus Viannia from the remaining Leishmania species, a divergence associated with profound changes in the parasite infectious cycle and virulence. The genus Leishmania therefore offers an accessible system for testing hypothesis about forces that may select for the loss of RNAi during evolution, such as invasion by viruses, changes in genome plasticity mediated by transposable elements and gene amplification (including those mediating drug resistance), and/or alterations in parasite virulence.