MOLECULAR PHYLOGENETIC ANALYSIS OF rbcL IN THE PRYMNESIOPHYTA¹

Abstract

The nucleotide sequences of rbcL genes encoding the large subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) were determined from six species of Prymnesiophyta to clarify their phylogenetic relationships. Molecular phylogenetic trees were constructed using PAUP (Phylogenetic Analysis Using Parsimony). These analyses suggest that the Prymnesiophyta, except for the Pavlovales, area relatively stable monophyletic group. Pleurochrysis carterae, included in the Isochrysidales, is a sister species of a monophyletic group consisting of other members of the Isochrysidales, Gephyrocapsa oceanica and Emiliania huxleyi, members of the Coccosphaerales, Calyptrosphaera sphaeroidea and Umbilicosphaera sibogae var. foliosa, and a member of the Prymnesiales, Chrysochromulina hirta. The nucleotide sequence of rbcL from G. oceanica was identical to that from E. huxleyi within the region examined. Our trees show that G. oceanica and E. huxleyi are more closely related to C. hirta than to U. sibogae, C. sphaeroidea, and P. carterae. These results suggest that orders in the Prymnesiophyceae, including the above‐mentioned genera, should be redefined.

Induction of Phase Variation Events in the Life Cycle of the Marine Coccolithophorid Emiliania huxleyi

“…Amplification the ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) large-subunit gene from E. huxleyi (14) was obtained with the following primers: 5Ј-ACTGCTACATGGACTGTAGTA-3Ј and 5Ј-TAGATCTAATGCAGTTTG AAG-3Ј. Single-colony isolates were picked from agar plates and resuspended in 15 l of Tris-EDTA buffer; 5 l of the resuspended cells was then used in a standard PCR with a 10-min hot start at 95°C and a 52°C annealing temperature.…”

A coccolithophore concept for constraining the Cenozoic carbon cycle

“…1a). Modern E. huxleyi and G. oceanica are distinct genetic outliers to most other extant coccolithophore (Fujiwara et al, 1994;Sáez et al, 2003), and group together with other alkenone-producing haptophytes such as the non-coccolith bearing species Isochrysis galbana. The morphospecies E. huxleyi had a first occurrence ∼291-268 ka and has risen to global dominance since 85 ka, while G. oceanica evolved at 1.7 Ma (Thierstein et al, 1977;Raffi et al, 2006).…”

Botánica y Evolución

“…contenidas) que también fué reducida aunque conservando su núcleo vestigial (117). Igualmente el ancestro de los primnesiófitos (= haptófitos o cocolitofóridos) independientemente, captó y redujo a un alga roja diferente (118 Más compleja es la historia de los plastos del conjunto pardo-dorado: quizá el antepasado común a sus linajes fotosintetizadores y pseudofún-gicos (laberintúlidos y oomicetes, diatomeas, crisófitos, xantófitos, algas pardas, pelagoficeas, silicoflagelados y pedinélidos) incorporó un alga roja unicelular (119,120) que fué reducida a crisoplasto; especies individuales o ramas enteras (como los laberintúlidos y oomicetes) lo perdieron secundariamente (algunas retienen mancha ocular como resto del mismo). Pero el plasto de eustigmatofíceas y, sobre todo los de rafidofíceas…”