title: Apicoplast genome of the coccidian Eimeria tenella.
abstract: Unicellular apicomplexans possess an algal-originated plastid referred to as an apicoplast. Although apicomplexan parasites are comprised of highly diverse protists, the complete apicoplast genome sequences have only been determined from the hematozoan Plasmodium falciparum and cyst-forming coccidian Toxoplasma gondii. Here, we report the third complete sequence of apicoplast genome from the intestinal coccidian Eimeria tenella that may serve as a new drug target against coccidiosis in the livestock. The AT-rich E. tenella plastid genome is a 35-kb circular element. Its gene organization resembles more closely that of T. gondii than P. falciparum. Although the E. tenella plastid genome contains an almost identical set of genes to that found in P. falciparum and T. gondii, its encoded genes share low or moderate homologies with their counterparts in the other two apicomplexans. With the addition of this coccidian plastid genome sequence, we attempted to reexamine the apicoplast genome evolution and performed phylogenetic reconstructions using maximum likelihood and Bayesian inference (BI) methods based on a concatenated dataset of plastid-encoded rpoB, rpoC1 and rpoC2 proteins. All resulting rpo protein trees placed apicoplast as a sister to Euglena within the green lineage. On the other hand, many recent studies based on the organization of plastid genes and some nuclear-encoded plastid proteins have supported a common red algal ancestry of apicomplexan and dinoflagellate plastids. If the apicoplast indeed originated from a red ancestor, the green relationship of apicomplexan genes would probably imply that the ancestral host that gave rise to the (red) apicoplast might have already contained some primary green plastid genes.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine, College Station, TX 77843-4467, USA.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Cai
authors.forename: A Lorraine
authors.initials: AL
authors.lastname: Fuller
authors.forename: Larry R
authors.initials: LR
authors.lastname: McDougald
authors.forename: Guan
authors.initials: G
authors.lastname: Zhu
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D004270:DNA, Circular / Q000737:chemistry / Q000235:genetics; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D016786:Eimeria tenella / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D018087:Plastids / Q000737:chemistry / Q000235:genetics*; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
chemical_list: D004270:DNA, Circular; D016054:DNA, Protozoan; D016053:RNA, Protozoan; D012321:DNA-Directed RNA Polymerases