Doetsch N A, Thompson M D, Favreau M R, Hallick R B
Department of Biochemistry, University of Arizona, Tucson 85721-0088, USA.
Mol Gen Genet. 2001 Jan;264(5):682-90. doi: 10.1007/s004380000355.
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.
在光合原生生物纤细裸藻中发现了一种新型混合操纵子。psbK、ycf12、psaM和trnR基因共转录。产生的四顺反子转录本通过基因间隔区的内切核酸酶切割和内含子剪接进行加工，形成三种成熟的单顺反子mRNA和一种tRNA。一个III类双内含子和一个III类内含子位于psbK中。在ycf12中发现了另一个III类内含子。通过PCR扩增从九个相关裸藻物种中克隆了psbK操纵子。在每个物种中，psbK操纵子的基因顺序和内容都是保守的。psbK操纵子包含系统发育上保守的真细菌启动子、翻译和3'加工元件。内含子含量在不同物种间差异显著。基于内含子含量与系统发育分析结果的比较，裸藻谱系内III类内含子的进化比之前认为的要复杂得多。
