DIVERSITY AND PHYLOGENETIC PLACEMENT OF BRACTEACOCCUS TEREG (CHLOROPHYCEAE, CHLOROPHYTA) BASED ON 18S RIBOSOMAL RNA GENE SEQUENCE DATA¹

Abstract

Sequence data from the nuclear small-subunit ribosomal RNA gene was obtained for nine strains of Bracteacoccus Tereg) representing at least Jive morphologzcal species and four distinct geographic locations. These, along with sequence data from two additional chlorophycean taxa, Spongiochloris spongiosa Starr and Ascochloris multinucleata Bold et MacEntee, and 48 published sequences from green algal taxa, were used to determine the phylogenetic placement of Bracteacoccus with respect to other chlorophycean green akae. Results support the monophyb of Bracteacoccus strains, contrasting with patterns o b served so far f m many other coccoid green algae. The range of variation among Bracteacoccus strains is similar to that of other congeners. Basal body orientation in Bracteacoccus has been interpreted as clockwise; however, the 18.5 data point to a relationship between Bracteacoccus and taxa with the directly opposed conJiguration of the flagellar apparatus. No close relationship was found to the multinucleated green coccoids with clockwise orientation of basal bodies, such as Spongiochloris, or to those with parallel basal bodies, such as Spermatozopsis. However, 18s data conJim that the motile and Vegetative cells of Bracteacoccus are structurally distinct from the representatives of sphaeroplealean families currently studied. It is premature to reclasszfy Bracteacoccus until 18s comparisons can be made with additional sphaeroplealean taxa and with algae with similar flagellar structure such as Dictyochloris and Heterochlamydomonas. Key index words: 18s rDNA sequence data; Chlorococcales; flagellar apparatus absolute orientationMolecular studies using sequence data from the nuclear small-subunit ribosomal RNA (rRNA) gene have greatly advanced our understanding of phylogenetic relationships of a variety of green algal groups (Buchheim et al.

Phylogeny and Molecular Evolution of the Green Algae

“…Monophyly of the Sphaeropleales has been supported by unique rDNA ITS2 secondary structure characteristics (Keller et al, 2008) and phylogenetic analysis of nuclear rDNA and plastid atpB and rbcL sequences (Verghese, 2007). Diversity and phylogenetic relationships within the Sphaeropleales have been studied by Lewis (1997), Krienitz et al (Krienitz et al, 2001;2011), , Shoup and Lewis (2003), Wolf et al (2003), McManus and Lewis (2005;2011) and Johnson et al (2007).…”

The Biological Soil Crusts of the San Nicolas Island: Enigmatic Algae from a Geographically Isolated Ecosystem

“…In some cases, nearly complete gene sequences (over 1700 nucleotides) were obtained. Primers for PCR amplification followed Lewis (1997). Double-stranded amplified product was sequenced in 20-μL volumes using 18S sequencing primer with an ABI PRISM system by reading electrophoresed labeled base calls.…”

Strain survey on three continents confirms the polyphyly of the genus Pediastrum (Hydrodictyaceae, Chlorophyceae).

“…and Pediastrum duplex Meyen (WiLcox et al 1992;LeWis 1997) and their placement within Sphaeropleales (BuchheiM et al 2001). An expanded phylogenetic analysis of 26S rRNA, 5.8S + ITS2 genes using sequences of seven strains of Hydrodictyon, 29 strains of Pediastrum and three strains of Sorastrum revealed a pattern of colony-form evolution within the family from twodimensionality to three-dimensionality (McManus & LeWis 2005).…”