Heterogeneity of intron presence/absence in Olifantiella sp. (Bacillariophyta) contributes to the understanding of intron loss |
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| Authors: | Jichang Han Lin Zhang Pu Wang Guanpin Yang Song Wang Yuhang Li Kehou Pan |
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| Institution: | 1. Laboratory of Applied Microalgae Biology, Ocean University of China, Qingdao, China;2. College of Marine, Ningbo University, Ningbo, China;3. Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, USA;4. College of Marine Life Sciences, Ocean University of China, Qingdao, China;5. Department of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China;6. Function Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China |
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| Abstract: | Although hypotheses have been proposed and developed to interpret the origins and functions of introns, substantial controversies remain about the mechanism of intron evolution. The availability of introns in the intermediate state is quite helpful for resolving this debate. In this study, a new strain of diatom (denominated as DB21‐1) was isolated and identified as Olifantiella sp., which possesses multiple types of 18S rDNAs (obtained from genomic DNA; lengths ranged from 2,056 bp to 2,988 bp). Based on alignments between 18S rDNAs and 18S rRNA (obtained from cDNA; 1,783 bp), seven intron insertion sites (IISs) located in the 18S rDNA were identified, each of which displayed the polymorphism of intron presence/absence. Specific primers around each IIS were designed to amplify the introns and the results indicated that introns in the same IIS varied in lengths, while terminal sequences were conserved. Our study showed that the process of intron loss happens via a series of successive steps, and each step could derive corresponding introns under intermediate states. Moreover, these results indicate that the mechanism of genomic deletion that occurs at DNA level can also lead to exact intron loss. |
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| Keywords: | 18S rRNA diatom intron evolution intron loss spliceosomal intron |
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