In:
BMC Evolutionary Biology, Springer Science and Business Media LLC, Vol. 8, No. 1 ( 2008-12)
Abstract:
Within Chlorophyceae the ITS2 secondary structure shows an unbranched helix I, except for the ' Hydrodictyon ' and the ' Scenedesmus ' clade having a ramified first helix. The latter two are classified within the Sphaeropleales, characterised by directly opposed basal bodies in their flagellar apparatuses (DO-group). Previous studies could not resolve the taxonomic position of the ' Sphaeroplea ' clade within the Chlorophyceae without ambiguity and two pivotal questions remain open: (1) Is the DO-group monophyletic and (2) is a branched helix I an apomorphic feature of the DO-group? In the present study we analysed the secondary structure of three newly obtained ITS2 sequences classified within the ' Sphaeroplea ' clade and resolved sphaeroplealean relationships by applying different phylogenetic approaches based on a combined sequence-structure alignment. Results The newly obtained ITS2 sequences of Ankyra judayi, Atractomorpha porcata and Sphaeroplea annulina of the ' Sphaeroplea ' clade do not show any branching in the secondary structure of their helix I. All applied phylogenetic methods highly support the ' Sphaeroplea ' clade as a sister group to the 'core Sphaeropleales'. Thus, the DO-group is monophyletic. Furthermore, based on characteristics in the sequence-structure alignment one is able to distinguish distinct lineages within the green algae. Conclusion In green algae, a branched helix I in the secondary structure of the ITS2 evolves past the ' Sphaeroplea ' clade. A branched helix I is an apomorph characteristic within the monophyletic DO-group. Our results corroborate the fundamental relevance of including the secondary structure in sequence analysis and phylogenetics.
Type of Medium:
Online Resource
ISSN:
1471-2148
DOI:
10.1186/1471-2148-8-218
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2008
detail.hit.zdb_id:
2041493-6
detail.hit.zdb_id:
3053924-9
SSG:
12
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