Polyphyletic origin of the genus Physarum (Physarales, Myxomycetes) revealed by nuclear rDNA mini-chromosomal analysis and group I intron synapomorphy

Physarales represents the largest taxonomic order among the plasmodial slime molds (myxomycetes). Physarales is of particular interest since the two best-studied myxomycete species, Physarum polycephalum and Didymium iridis, belong to this order and are currently subjected to whole genome and transc...

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Bibliographic Details
Published in:	BMC evolutionary biology
Main Authors:	Nandipati, Satish C R, Haugli, Kari B, Coucheron, Dag-Hugo, Haskins, Edward F, Johansen, Steinar
Format:	Journal Article
Language:	English
Published:	BioMed Central 2012
Subjects:	Basale biofag: 470 Basic biosciences: 470 Genetics and genomics: 474 Genetikk og genomikk: 474 Matematikk og Naturvitenskap: 400 Mathematics and natural science: 400 Molecular biology: 473 Molekylærbiologi: 473 VDP
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Summary:	Physarales represents the largest taxonomic order among the plasmodial slime molds (myxomycetes). Physarales is of particular interest since the two best-studied myxomycete species, Physarum polycephalum and Didymium iridis, belong to this order and are currently subjected to whole genome and transcriptome analyses. Here we report molecular phylogeny based on ribosomal DNA (rDNA) sequences that includes 57 Physarales isolates. The Physarales nuclear rDNA sequences were found to be loaded with 222 autocatalytic group I introns, which may complicate correct alignments and subsequent phylogenetic tree constructions. Phylogenetic analysis of rDNA sequences depleted of introns confirmed monophyly of the Physarales families Didymiaceae and Physaraceae. Whereas good correlation was noted between phylogeny and taxonomy among the Didymiaceae isolates, significant deviations were seen in Physaraceae. The largest genus, Physarum, was found to be polyphyletic consisting of at least three well supported clades. A synapomorphy, located at the highly conserved G-binding site of L2449 group I intron ribozymes further supported the Physarum clades. Our results provide molecular relationship of Physarales genera, species, and isolates. This information is important in further interpretations of comparative genomics nd transcriptomics. In addition, the result supports a polyphyletic origin of the genus Physarum and calls for a reevaluation of current taxonomy.
ISSN:	1471-2148 1471-2148
DOI:	10.1186/1471-2148-12-166