Helms, Gert

[["dc.bibliographiccitation.firstpage","74"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Journal of Molecular Evolution"],["dc.bibliographiccitation.lastpage","84"],["dc.bibliographiccitation.volume","55"],["dc.contributor.author","Bhattacharya, Debashish"],["dc.contributor.author","Friedl, Thomas"],["dc.contributor.author","Helms, Gert"],["dc.date.accessioned","2018-11-07T10:22:13Z"],["dc.date.available","2018-11-07T10:22:13Z"],["dc.date.issued","2002"],["dc.description.abstract","One family within the Euascomycetes (Ascomycota), the lichen-forming Physciaceae, is particularly rich in nuclear ribosomal [r]DNA group I introns. We used phylogenetic analyses of group I introns and lichen-fungal host cells to address four questions about group I intron evolution in lichens, and generally in all eukaryotes: 1) Is intron spread in the lichens associated with the intimate association of the fungal and photosynthetic cells that make Lip the lichen thallus? 2) Are the Multiple group I introns in the lichen-fungi of independent origins, or have existing introns spread into novel sites in the rDNA? 3) If introns have moved to novel sites, then does the exon context of these sites provide insights into the mechanism of intron spread? and 4) What is the pattern of intron loss in the small subunit rDNA gene of lichen-fungi? Our analyses show that group I introns in the lichen-fungi and in the lichen-algae (and lichenized cyanobacteria) do not share a close evolutionary relationship, suggesting that these introns do not move between the symbionts. Many group I introns appear to have originated in the common ancestor of the Lecanorales, whereas others have spread within this lineage (particularly in the Physciaceae) putatively through reverse-splicing into novel rRNA sites. We suggest that the evolutionary history of most lichen-fungal group I introns is characterized by rare gains followed by extensive losses in descendants, resulting in a sporadic intron distribution. Detailed phylogenetic analyses of the introns and host cells are required, therefore, to distinguish this scenario from the alternative hypothesis of widespread and independent intron gains in the different lichen-fungal lineages."],["dc.identifier.doi","10.1007/s00239-001-2305-x"],["dc.identifier.isi","000176243200007"],["dc.identifier.pmid","12165844"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/42237"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.submitter","Najko"],["dc.relation.issn","0022-2844"],["dc.title","Vertical evolution and intragenic spread of lichen-fungal group I introns"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","434"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Journal of Molecular Evolution"],["dc.bibliographiccitation.lastpage","446"],["dc.bibliographiccitation.volume","60"],["dc.contributor.author","Simon, Dawn"],["dc.contributor.author","Moline, Jessica"],["dc.contributor.author","Helms, Gert"],["dc.contributor.author","Friedl, Thomas"],["dc.contributor.author","Bhattacharya, Debashish"],["dc.date.accessioned","2018-11-07T11:12:22Z"],["dc.date.available","2018-11-07T11:12:22Z"],["dc.date.issued","2005"],["dc.description.abstract","The wide but sporadic distribution of group I introns in protists, plants, and fungi, as well as in eubacteria, likely resulted from extensive lateral transfer followed by differential loss. The extent of horizontal transfer of group I introns can potentially be determined by examining closely related species or genera. We used a phylogenetic approach with a large data set (including 62 novel large subunit [LSU] rRNA group I introns) to study intron movement within the monophyletic lichen family Physciaceae. Our results show five cases of horizontal transfer into homologous sites between species but do not support transposition into ectopic sites. This is in contrast to previous work with Physciaceae small subunit (SSU) rDNA group I introns where strong support Was found for multiple ectopic transpositions. This difference in the apparent number of ectopic intron movements between SSU and LSU rDNA genes may in part be explained by a larger number of positions in the SSU rRNA, which can Support the insertion and/or retention of group I introns. In contrast. we suggest that the LSU rRNA may have fewer acceptable positions and therefore intron spread is limited in this gene."],["dc.identifier.doi","10.1007/s00239-004-0152-2"],["dc.identifier.isi","000228836500003"],["dc.identifier.pmid","15883879"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53649"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.submitter","Najko"],["dc.relation.issn","0022-2844"],["dc.title","Divergent histories of rDNA group I introns in the lichen family Physciaceae"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]