March 1999, Volume 150, Issue 1, Pages 33 - 42

Original Paper

Phylogenetic Affinities of Diplonema within the Euglenozoa as Inferred from the SSU rRNA Gene and Partial COI Protein Sequences Dmitri A Maslov 1,3 , Shinji Yasuhira 2,4 & Larry Simpson2 1Department of Biology, University of California, Riverside, CA 92521, USA     2Howard Hughes Medical Institute, Department of Molecular, Cell and Developmental Biology and Department of Medical Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095-1662, USA     3Corresponding author; fax 1-909-787-4286 E-mail: maslov@ucrac1.ucr.edu 4Present address: Research Reactor Institute, Kyoto University, Kumatori-cho, Noda, Sennan-gun, Osaka 590-04, Japan

Keywords

Cytochrome oxidase;   Diplonema papillatum;   Euglenozoa;   Isonema;   phylogeny;   small subunit rRNA

Abstract

In order to shed light on the phylogenetic position of diplonemids within the phylum Euglenozoa, we have sequenced small subunit rRNA (SSU rRNA) genes from Diplonema (syn. Isonema) papillatum and Diplonema sp. We have also analyzed a partial sequence of the mitochondrial gene for cytochrome c oxidase subunit I from D. papillatum. With both markers, the maximum likelihood method favored a closer grouping of diplonemids with kinetoplastids, while the parsimony and distance suggested a closer relationship of diplonemids with euglenoids. In each case, the differences between the best tree and the alternative trees were small. The frequency of codon usage in the partial D. papillatum COI was different from both related groups; however, as is the case in kinetoplastids but not in Euglena, both the non-canonical UGA codon and the canonical UGG codon were used to encode tryptophan in Diplonema.

Received 4 November 1998; Accepted 6 February 1999

^© Macmillan Publishers Ltd 1999