Sequential splicing of a group II twintron in the marine cyanobacterium <i>Trichodesmiume</i>

作     者：Pfreundt, Ulrike Hess, Wolfgang R. 

作者机构：Univ Freiburg Fac Biol D-79104 Freiburg Germany 

出 版 物：《SCIENTIFIC REPORTS》 (科学报告)

年 卷 期：2015年第5卷第1期

页      面：16829-16829页

核心收录：

学科分类：12[管理学] 1201[管理学-管理科学与工程(可授管理学、工学学位)] 08[工学] 

基　　金：GERMAN-ISRAELI RESEARCH FOUNDATION (GIF) [1133-13.8/2011] European Union project MaCuMBA (Marine Microorganisms: Cultivation Methods for Improving their Biotechnological Applications) 

主　　题：TRICHODESMIUM NON-coding DNA INTRONS RNA splicing GENOMES 

摘      要：The marine cyanobacterium Trichodesmium is unusual in its genomic architecture as 40% of the genome is occupied by non-coding DNA. Although the majority of it is transcribed into RNA, it is not well understood why such a large non-coding genome fraction is maintained. Mobile genetic elements can contribute to genome expansion. Many bacteria harbor introns whereas twintrons, introns-in-introns, are rare and not known to interrupt protein-coding genes in bacteria. Here we show the sequential in vivo splicing of a 5400 nt long group II twintron interrupting a highly conserved gene that is associated with RNase HI in some cyanobacteria, but free-standing in others, including Trichodesmium erythraeum. We show that twintron splicing results in a putatively functional mRNA. The full genetic arrangement was found conserved in two geospatially distinct metagenomic datasets supporting its functional relevance. We further show that splicing of the inner intron yields the free intron as a true circle. This reaction requires the spliced exon reopening (SER) reaction to provide a free 5 exon. The fact that Trichodesmium harbors a functional twintron fits in well with the high intron load of these genomes, and suggests peculiarities in its genetic machinery permitting such arrangements.