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Title: Babesia bovis: a comprehensive phylogenetic analysis of plastid-encoded genes supports green algal origin of apicoplasts

Author
item LAU, AUDREY - Washington State University
item MCELWAIN, TERRY - Washington State University
item BRAYTON, KELLY - Washington State University
item Knowles Jr, Donald
item ROALSON, ERIC - Washington State University

Submitted to: Experimental Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2009
Publication Date: 11/1/2009
Citation: Lau, A.O., Mcelwain, T.F., Brayton, K.A., Knowles Jr, D.P., Roalson, E.H. 2009. Babesia bovis: a comprehensive phylogenetic analysis of plastid-encoded genes supports green algal origin of apicoplasts. Experimental Parasitology. 123(3):236-243.

Interpretive Summary: Plastids are major organelles found in the cells of plants and algae and are the site for important genes which products are used by the cell. Apicoplasts are a form of plastid found in most Apicomplexa including Babesia bovis, an important pathogen of cattle and the cause of Tick Fever in cattle. Because apicoplasts are vital to parasite survival, they provide important potential targets for anti-babesial drugs. Comparative analysis of apicomplexa from a diversity of organisms provides the opportunity to detect novel biosynthetic pathways, such as de novo fatty acid synthesis in malaria, which may provide unique anti-babesial drug targets. The long term impact for U. S. Agriculture includes the identification of novel pathways in babesial parasites of cattle and horses which can be used for parasite control and possible clearance.

Technical Abstract: Apicomplexan parasites commonly contain a unique, non-photosynthetic plastid-like organelle termed the apicoplast. Previous analyses of other plastid-containing organisms suggest that apicoplasts were derived from a red algal ancestor. In this report, we present an extensive phylogenetic study of apicoplast origins using multiple previously reported apicoplast sequences as well as several sequences recently reported. Phylogenetic analysis of amino acid sequences was used to determine the evolutionary origin of the organelle. A total of nine plastid genes from 37 species were incorporated in our study. The data strongly support a green algal origin for apicoplasts and Euglenozoan plastids. Further, the nearest green algae lineage to the Apicomplexans is the parasite Helicosporidium, suggesting that apicoplasts may have originated by lateral transfer from green algal parasite lineages. The results also substantiate earlier findings that plastids found in Heterokonts such as Odontella and Thalassiosira were derived from a separate secondary endosymbiotic event likely originating from a red algal lineage.