PHYLOGENETIC ANALYSIS OF 32 STRAINS OFVAUCHERIA(XANTHOPHYCEAE) USING THErbcL GENE AND ITS TWO FLANKING SPACER REGIONS¹

Abstract

The complete rbcL gene was sequenced for 21 species and 32 strains of Vaucheria and for five other Xanthophyceae (Asterosiphon dichotomus (Kützing) Rieth, Botrydium becharianum Vischer, B. cystosum Vischer, B. stoloniferum Mitra, Tribonema intermixtum Pascher). The psbA‐rbcL spacer, upstream of the rbcL gene, and the RUBISCO spacer between the rbcL and rbcS genes were also completely sequenced for the Vaucheria strains and Asterosiphon. The psbA‐rbcL spacer was the most variable region that was sequenced, and only the 3′ end of the spacer could be aligned. Phylogenetic analyses (maximum parsimony, neighbor joining, and maximum likelihood) were conducted using the DNA sequence and the amino acid sequence for the rbcL gene, and a second analysis was conducted using a portion of the psbA‐rbcL spacer +rbcL gene + RUBISCO spacer. All analyses showed that Vaucheria species formed monophyletic clades that corresponded with morphologically based subgeneric sections, including the section Racemosae. Species producing a gametophore (= fruiting branch, bearing both an antheridium and oogonium) formed a monophyletic clade in all analyses. The nongametophore species sometimes formed a monophyletic clade but other times formed a basal grade. Pair‐wise comparisons of nucleotides and amino acids showed that for some species, numerous nucleotide changes resulted in relatively few amino acid changes. Consequently, phylogenetic analysis of the amino acids produced numerous trees, which in a strict consensus tree resulted in numerous polychotomies. An original strain of V. terrestris that was deposited in two culture collections over 25 years ago had identical sequences, suggesting no rapid change was occurring in the sequenced regions. Two strains of V. prona, isolated from Europe and North America, had identical sequences. Other species, for which two or more strains were examined, had different sequences. These results suggest that cryptic species complexes exist within Vaucheria because the rbcL gene is a conservative gene that is identical in other protists.

O gênero Vaucheria D.C. (Vaucheriaceae, Xanthophyceae) no sul do Brasil: aspectos taxonômicos e ecológicos

“…Rieth (1980) e Entwisle (1988), por sua vez, propuseram a subdivisão do gênero em várias seções. Tais propostas, especialmente a de Entwisle (1988), foram corroboradas por Andersen & Bailey (2002) que estudaram a filogenia do grupo através da análise de sequências de DNA (gene rbcL e espaçadores psbA-rbcL e RUBISCO entre rbcL e rbcS).…”

Genetic variation in bloom-forming ichthyotoxicPseudochattonellaspecies (Dictyochophyceae, Heterokonta) using nuclear, mitochondrial and plastid DNA sequence data

“…The psbA (Wee et al, 1996) and rbcL (Daugbjerg & Andersen, 1997) regions have been utilized to differentiate between major classes. The RuBisCO spacer has been widely used for phylogenetic studies within the Phaeophyceae (Rohfritsch et al, 2007) and in studies of intraspecific variation within the classes Pelagophyceae (Bailey & Andersen, 1999) and Xanthophyceae (Andersen & Bailey, 2002). The presence of these genes in high copy numbers in the genome in three different cell compartments, combined with the availability of sequences in public databases, make them attractive markers for studies of phylogeny and genetic variability.…”

“…Nuclear-encoded ribosomal DNA and plastid-encoded genes have for several years successfully been applied to identify heterokonts (Andersen & Bailey, 2002;Ki & Han, 2007), to infer their phylogenetic relationships (e.g. Ben Ali et al, 2002), and to reveal genetic diversity (e.g.…”