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Collodictyon--an ancient lineage in the tree of eukaryotes.

Zhao S, Burki F, Bråte J, Keeling PJ, Klaveness D, Shalchian-Tabrizi K - Mol. Biol. Evol. (2012)

Bottom Line: Collodictyon shares cellular characteristics with Excavata and Amoebozoa, such as ventral feeding groove supported by microtubular structures and the ability to form thin and broad pseudopods.These may therefore be ancient morphological features among eukaryotes.Overall, this shows that Collodictyon is a key lineage to understand early eukaryote evolution.

View Article: PubMed Central - PubMed

Affiliation: Microbial Evolution Research Group, Department of Biology, University of Oslo, Oslo, Norway.

ABSTRACT
The current consensus for the eukaryote tree of life consists of several large assemblages (supergroups) that are hypothesized to describe the existing diversity. Phylogenomic analyses have shed light on the evolutionary relationships within and between supergroups as well as placed newly sequenced enigmatic species close to known lineages. Yet, a few eukaryote species remain of unknown origin and could represent key evolutionary forms for inferring ancient genomic and cellular characteristics of eukaryotes. Here, we investigate the evolutionary origin of the poorly studied protist Collodictyon (subphylum Diphyllatia) by sequencing a cDNA library as well as the 18S and 28S ribosomal DNA (rDNA) genes. Phylogenomic trees inferred from 124 genes placed Collodictyon close to the bifurcation of the "unikont" and "bikont" groups, either alone or as sister to the potentially contentious excavate Malawimonas. Phylogenies based on rDNA genes confirmed that Collodictyon is closely related to another genus, Diphylleia, and revealed a very low diversity in environmental DNA samples. The early and distinct origin of Collodictyon suggests that it constitutes a new lineage in the global eukaryote phylogeny. Collodictyon shares cellular characteristics with Excavata and Amoebozoa, such as ventral feeding groove supported by microtubular structures and the ability to form thin and broad pseudopods. These may therefore be ancient morphological features among eukaryotes. Overall, this shows that Collodictyon is a key lineage to understand early eukaryote evolution.

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18S + 28S rDNA phylogeny of Collodictyon triciliatum (highlighted by black box) reconstructed with MrBayes v3.1.2 under the GTR + GAMMA+I + covarion model. Numbers at nodes are PP and ML bootstrap values (BP, inferred by RAxML v7.2.6 under the GTR + GAMMA + I model). Thick lines show PP > 0.9 and BP > 80%. Nodes marked with symbol “-” indicate BP < 50% or PP < 0.5. Some branches are shortened by half in order to save space (marked with “/”).
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fig2: 18S + 28S rDNA phylogeny of Collodictyon triciliatum (highlighted by black box) reconstructed with MrBayes v3.1.2 under the GTR + GAMMA+I + covarion model. Numbers at nodes are PP and ML bootstrap values (BP, inferred by RAxML v7.2.6 under the GTR + GAMMA + I model). Thick lines show PP > 0.9 and BP > 80%. Nodes marked with symbol “-” indicate BP < 50% or PP < 0.5. Some branches are shortened by half in order to save space (marked with “/”).

Mentions: To improve the rDNA tree, we also sequenced the 28S rDNA gene for Collodictyon and reconstructed a combined 18S + 28S rDNA phylogeny (fig. 2). This tree showed Collodictyon as a deep lineage with possible affinity to Excavata with 45% BP and 0.99 PP. Interestingly, our data did not show any affiliation to Apusozoa, even though this group has been proposed to be closely related to Collodictyon (Cavalier-Smith 2003). Instead, the 18S + 28S rDNA tree suggested Apusomonas to be sister to Amoebozoa (56% BP and 1.00 PP), although Ancyromonas grouped with the Opisthokonta (<50% BP and 1.00 PP).


Collodictyon--an ancient lineage in the tree of eukaryotes.

Zhao S, Burki F, Bråte J, Keeling PJ, Klaveness D, Shalchian-Tabrizi K - Mol. Biol. Evol. (2012)

18S + 28S rDNA phylogeny of Collodictyon triciliatum (highlighted by black box) reconstructed with MrBayes v3.1.2 under the GTR + GAMMA+I + covarion model. Numbers at nodes are PP and ML bootstrap values (BP, inferred by RAxML v7.2.6 under the GTR + GAMMA + I model). Thick lines show PP > 0.9 and BP > 80%. Nodes marked with symbol “-” indicate BP < 50% or PP < 0.5. Some branches are shortened by half in order to save space (marked with “/”).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3351787&req=5

fig2: 18S + 28S rDNA phylogeny of Collodictyon triciliatum (highlighted by black box) reconstructed with MrBayes v3.1.2 under the GTR + GAMMA+I + covarion model. Numbers at nodes are PP and ML bootstrap values (BP, inferred by RAxML v7.2.6 under the GTR + GAMMA + I model). Thick lines show PP > 0.9 and BP > 80%. Nodes marked with symbol “-” indicate BP < 50% or PP < 0.5. Some branches are shortened by half in order to save space (marked with “/”).
Mentions: To improve the rDNA tree, we also sequenced the 28S rDNA gene for Collodictyon and reconstructed a combined 18S + 28S rDNA phylogeny (fig. 2). This tree showed Collodictyon as a deep lineage with possible affinity to Excavata with 45% BP and 0.99 PP. Interestingly, our data did not show any affiliation to Apusozoa, even though this group has been proposed to be closely related to Collodictyon (Cavalier-Smith 2003). Instead, the 18S + 28S rDNA tree suggested Apusomonas to be sister to Amoebozoa (56% BP and 1.00 PP), although Ancyromonas grouped with the Opisthokonta (<50% BP and 1.00 PP).

Bottom Line: Collodictyon shares cellular characteristics with Excavata and Amoebozoa, such as ventral feeding groove supported by microtubular structures and the ability to form thin and broad pseudopods.These may therefore be ancient morphological features among eukaryotes.Overall, this shows that Collodictyon is a key lineage to understand early eukaryote evolution.

View Article: PubMed Central - PubMed

Affiliation: Microbial Evolution Research Group, Department of Biology, University of Oslo, Oslo, Norway.

ABSTRACT
The current consensus for the eukaryote tree of life consists of several large assemblages (supergroups) that are hypothesized to describe the existing diversity. Phylogenomic analyses have shed light on the evolutionary relationships within and between supergroups as well as placed newly sequenced enigmatic species close to known lineages. Yet, a few eukaryote species remain of unknown origin and could represent key evolutionary forms for inferring ancient genomic and cellular characteristics of eukaryotes. Here, we investigate the evolutionary origin of the poorly studied protist Collodictyon (subphylum Diphyllatia) by sequencing a cDNA library as well as the 18S and 28S ribosomal DNA (rDNA) genes. Phylogenomic trees inferred from 124 genes placed Collodictyon close to the bifurcation of the "unikont" and "bikont" groups, either alone or as sister to the potentially contentious excavate Malawimonas. Phylogenies based on rDNA genes confirmed that Collodictyon is closely related to another genus, Diphylleia, and revealed a very low diversity in environmental DNA samples. The early and distinct origin of Collodictyon suggests that it constitutes a new lineage in the global eukaryote phylogeny. Collodictyon shares cellular characteristics with Excavata and Amoebozoa, such as ventral feeding groove supported by microtubular structures and the ability to form thin and broad pseudopods. These may therefore be ancient morphological features among eukaryotes. Overall, this shows that Collodictyon is a key lineage to understand early eukaryote evolution.

Show MeSH