On the monophyly of chromalveolates using a six-protein phylogeny of eukaryotes

Abstract

A global phylogeny of major eukaryotic lineages is a significant and ongoing challenge to molecular phylogenetics. Currently, there are five hypothesized major lineages or 'supergroups' of eukaryotes. One of these, the chromalveolates, represents a large fraction of protist and algal diversity. The chromalveolate hypothesis was originally based on similarities between the photosynthetic organelles (plastids) found in many of its members and has been supported by analyses of plastid-related genes. However, since plastids can move between eukaryotic lineages, it is important to provide additional support from data generated from the nuclear-cytosolic host lineage. Genes coding for six different cytosolic proteins from a variety of chromalveolates (yielding 68 new gene sequences) have been characterized so that multiple gene analyses, including all six major lineages of chromalveolates, could be compared and concatenated with data representing all five hypothesized supergroups. Overall support for much of the phylogenies is decreased over previous analyses that concatenated fewer genes for fewer taxa. Nevertheless, four of the six chromalveolate lineages (apicomplexans, ciliates, dinoflagellates and heterokonts) consistently form a monophyletic assemblage, whereas the remaining two (cryptomonads and haptophytes) form a weakly supported group. Whereas these results are consistent with the monophyly of chromalveolates inferred from plastid data, testing this hypothesis is going to require a substantial increase in data from a wide variety of organisms.

Molecular Systematics and the Diatom Species

“…Development of these markers poses a critically important, though formidable, challenge for species research in diatoms. Several low-copy nuclear markers have been developed and successfully applied to a range of diatoms (Harper et al 2005), but these might not be informative for species-level comparisons. Near-universal primers are available for diatom silicon transporter genes (Thamatrakoln et al 2006), which do resolve closely related species (Alverson 2007).…”

Protein targeting into complex diatom plastids: functional characterisation of a specific targeting motif

“…Secondary endocytobiosis was a key event during the evolution of a variety of organisms and was found to have occurred at least twice, as some complex plastids have a green algal origin while others are related to red algae (Cavalier-Smith 1999. There is increasing evidence that the secondary plastids of the red algal lineage originate from a single endosymbiotic event and that the resulting chromalveolates (including heterokonts, cryptophytes, haptophytes, apicomplexa and dinoflagellates) might be monophyletic (Cavalier-Smith 1999;Harper et al 2005). While cryptophytes still possess a remnant nucleus of the endosymbiont, the nucleomorph, which is located in the periplastidic space between the second and third envelope membrane, in heterokonts (including diatoms) the reduction of the endosymbiont included the loss of the endosymbiont's nucleus, the mitochondria and all other cytoplasmatic components (Keeling 2004).…”

RXLR-Mediated Entry of Phytophthora sojae Effector Avr1b into Soybean Cells Does Not Require Pathogen-Encoded Machinery

“…Oomycetes are fungal-like organisms that are evolutionarily related to marine algae (Fö rster et al, 1990;Sogin and Silberman, 1998;Harper et al, 2005). Many oomycete species are destructive plant pathogens, including the potato late blight pathogen that caused the Irish potato famine, Phytophthora infestans, the Sudden Oak Death pathogen, Phytophthora ramorum, and the soybean root and stem rot pathogen Phytophthora sojae (Erwin and Ribiero, 1996).…”