On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas Systems
Reverse transcriptases (RTs) closely related to those encoded by group II introns but lacking the intron RNA structure have been found associated with type III clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems, a prokaryotic immune system against invading viruses and for...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2018-06-01
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| Series: | Frontiers in Microbiology |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/article/10.3389/fmicb.2018.01317/full |
| _version_ | 1818065011454509056 |
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| author | Nicolás Toro Francisco Martínez-Abarca Alejandro González-Delgado Mario Rodríguez Mestre |
| author_facet | Nicolás Toro Francisco Martínez-Abarca Alejandro González-Delgado Mario Rodríguez Mestre |
| author_sort | Nicolás Toro |
| collection | DOAJ |
| description | Reverse transcriptases (RTs) closely related to those encoded by group II introns but lacking the intron RNA structure have been found associated with type III clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems, a prokaryotic immune system against invading viruses and foreign genetic elements. Two models have been proposed to explain the origin and evolutionary relationships of these RTs: (i) the “single point of origin” model, according to which these RTs originated from a single acquisition event in bacterial, with the various protein domains (RT, RT-Cas1, and Cas6-RT-Cas1 fusions) corresponding to single points in evolution; and (ii) the “various origins” model, according to which, independent acquisition events in different evolutionary episodes led to these fusions. We tested these alternative hypotheses, by analyzing and integrating published datasets of RT sequences associated with CRISPR-Cas systems and inferring phylogenetic trees by maximum likelihood (ML) methods. The RTs studied could be grouped into 13 clades, mostly in bacteria, in which they probably evolved. The various clades appear to form three independent lineages in bacteria and a recent lineage in archaea. Our data show that the Cas6 domain was acquired twice, independently, through RT-Cas1 fusion, in the bacterial lineages. Taken together, there more evidence to support the “various origins” hypothesis. |
| first_indexed | 2024-12-10T14:45:06Z |
| format | Article |
| id | doaj.art-d82338795bef4dc8a3b2f1ec222c8b36 |
| institution | Directory Open Access Journal |
| issn | 1664-302X |
| language | English |
| last_indexed | 2024-12-10T14:45:06Z |
| publishDate | 2018-06-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Microbiology |
| spelling | doaj.art-d82338795bef4dc8a3b2f1ec222c8b362022-12-22T01:44:35ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2018-06-01910.3389/fmicb.2018.01317377012On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas SystemsNicolás ToroFrancisco Martínez-AbarcaAlejandro González-DelgadoMario Rodríguez MestreReverse transcriptases (RTs) closely related to those encoded by group II introns but lacking the intron RNA structure have been found associated with type III clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems, a prokaryotic immune system against invading viruses and foreign genetic elements. Two models have been proposed to explain the origin and evolutionary relationships of these RTs: (i) the “single point of origin” model, according to which these RTs originated from a single acquisition event in bacterial, with the various protein domains (RT, RT-Cas1, and Cas6-RT-Cas1 fusions) corresponding to single points in evolution; and (ii) the “various origins” model, according to which, independent acquisition events in different evolutionary episodes led to these fusions. We tested these alternative hypotheses, by analyzing and integrating published datasets of RT sequences associated with CRISPR-Cas systems and inferring phylogenetic trees by maximum likelihood (ML) methods. The RTs studied could be grouped into 13 clades, mostly in bacteria, in which they probably evolved. The various clades appear to form three independent lineages in bacteria and a recent lineage in archaea. Our data show that the Cas6 domain was acquired twice, independently, through RT-Cas1 fusion, in the bacterial lineages. Taken together, there more evidence to support the “various origins” hypothesis.https://www.frontiersin.org/article/10.3389/fmicb.2018.01317/fullCas1CRISPR-Cas systemgenome evolutiongroup II intronsretroelementsreverse transcriptase |
| spellingShingle | Nicolás Toro Francisco Martínez-Abarca Alejandro González-Delgado Mario Rodríguez Mestre On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas Systems Frontiers in Microbiology Cas1 CRISPR-Cas system genome evolution group II introns retroelements reverse transcriptase |
| title | On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas Systems |
| title_full | On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas Systems |
| title_fullStr | On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas Systems |
| title_full_unstemmed | On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas Systems |
| title_short | On the Origin and Evolutionary Relationships of the Reverse Transcriptases Associated With Type III CRISPR-Cas Systems |
| title_sort | on the origin and evolutionary relationships of the reverse transcriptases associated with type iii crispr cas systems |
| topic | Cas1 CRISPR-Cas system genome evolution group II introns retroelements reverse transcriptase |
| url | https://www.frontiersin.org/article/10.3389/fmicb.2018.01317/full |
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