title: Comparison of psbK operon organization and group III intron content in chloroplast genomes of 12 Euglenoid species.
abstract: A novel mixed operon has been identified in the photosynthetic protist E. gracilis. The genes for psbK, ycf12, psaM, and trnR are co-transcribed. The resulting tetracistronic transcripts are processed through endonucleolytic cleavage of the intergenic spacers and intron splicing to form three mature monocistronic mRNAs and a tRNA. A group III twintron and a group III intron are located in psbK. Another group III intron is found in ycf12. The psbK operon has been cloned by PCR amplification from nine related Euglenoid species. In each species, the gene order and content of the psbK operon is conserved. The psbK operons contain phylogenetically conserved eubacterial promoter, translational, and 3' processing elements. Intron content varies significantly from species to species. Based on a comparison of the intron content with the results of phylogenetic analysis, group III intron evolution within the Euglenoid lineage is much more complex than previously believed.
authors.affiliation: Department of Biochemistry, University of Arizona, Tucson 85721-0088, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Doetsch
authors.forename: M D
authors.initials: MD
authors.lastname: Thompson
authors.forename: M R
authors.initials: MR
authors.lastname: Favreau
authors.forename: R B
authors.initials: RB
authors.lastname: Hallick
mesh_terms: D020418:Algal Proteins; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002736:Chloroplasts / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D005055:Euglena / Q000235:genetics*; D019143:Evolution, Molecular; D005091:Exons; D016678:Genome; D007438:Introns; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D009876:Operon / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D010802:Phylogeny; D010940:Plant Proteins / Q000378:metabolism*; D015800:Protozoan Proteins; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
chemical_list: D020418:Algal Proteins; D018076:DNA, Complementary; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D012343:RNA, Transfer