Phylogenetic analyses of various euglenoid taxa (euglenozoa) based on 18s rdna sequence data

Abstract

18S rRNA genes (SSU rDNA) of five newly sequenced species were used as molecular markers to infer phylogenetic relationships within the euglenoids. Two members of the order Euglenales ( Lepocinclis ovata Playfair , Phacus similis Christen), two of the order Eutreptiales ( Distigma proteus Ehrenberg , D. curvata Pringsheim) and Gyropaigne lefévrei Bourelly et Georges of the order Rhabdomonadales were used in parsimony, maximum likelihood, and distance analyses. All trees derived from SSU rRNA data strongly supported the monophyletic origin of the Euglenozoa, with kinetoplastids as sister clade to the euglenoids and Petalomonas cantuscygni Cann et Pennick diverging at the base of the monophyletic euglenoid lineage. The data also supported the theory that phagotrophic euglenoids arose prior to osmotrophs and phototrophs. A lineage of Peranema trichophorum Ehrenberg and all sequenced Euglenales formed a sister clade to the osmotrophs. This suggests that the evolution of phototrophy within the euglenoids radiated from a single event.

Phylogenetic position and inter-relationships of the osmotrophic euglenids based on SSU rDNA data, with emphasis on the Rhabdomonadales (Euglenozoa).

“…Recently published molecular data with the SSU rDNA (Montegut-Felkner & Triemer, 1997 ;Linton et al, 1999Linton et al, , 2000Preisfeld et al, 2000) support the monophyly of the Euglenozoa and of the sister clades kinetoplastids and euglenids. Maslov et al (1999) who analysed two Diplonema SSU rDNA sequences and one COI sequence of Diplonema papillatum could not resolve the inter-relationships within the Euglenozoa.…”

“…Euglenid sequences were aligned to available sequences of euglenozoan and outgroup organisms. A preliminary alignment was performed using   (Thompson et al, 1997), with gap opening penalty 10, gap-extension penalty 0n5, and DNA weight matrix IUB (Preisfeld et al, 2000). It was necessary to correct the alignments manually by means of secondary structure based on the models of Euglena gracilis, Petalo-Phylogeny of euglenid osmotrophs monas cantuscygni, Peranema trichophorum, Khawkinea quartana, Bodo caudatus, Trypanosoma brucei and Saccharomyces cerevisiae SSU rRNA obtained from the rRNA web server ( Van de Peer et al, 2000) with the help of GeneDoc (Nicholas & Nicholas, 1997).…”

“…According to morphological resemblance (CavalierSmith, 1981 ;Kivic & Walne, 1984) and to molecular data (Montegut-Felkner & Triemer, 1997 ;Linton et al, 1999Linton et al, , 2000Maslov et al, 1999 ;Preisfeld et al, 2000) euglenids and kinetoplastids have been placed in a supertaxon Euglenozoa (Cavalier-Smith, 1981). This was extended to include the genus Diplonema (Cavalier-Smith, 1993 ;Montegut-Felkner & Triemer, 1994, 1996 and Postgaardi (Simpson, 1997) cells whose systematic position still remains unclear.…”

“…The phototrophic species of the Euglenales, including the secondary osmotrophs Astasia longa and Khawkinea quartana, and the phototrophic Eutreptiales form a monophyletic assemblage with the phagotrophic taxon Peranema trichophorum (Heteronematales) as next relative (Montegut-Felkner & Triemer, 1997 ;Linton et al, 1999Linton et al, , 2000Preisfeld et al, 2000). At the molecular level, little is known about the phagotrophic and the osmotrophic euglenids.…”

“…DNA isolation, amplification and sequencing. Isolation of DNA, amplification and sequencing of SSU rDNA was performed as described elsewhere (Preisfeld et al, 2000). Briefly, oligonucleotides specific to conserved regions of eukaryotic SSU rDNA were used as primers for PCR with REDTaq DNA polymerase (Sigma) as reaction enzyme.…”