Sterols in a unicellular relative of the metazoans

@article{Kodner2008SterolsIA,
  title={Sterols in a unicellular relative of the metazoans},
  author={Robin B. Kodner and Roger Everett Summons and Ann Pearson and Nicole King and Andrew H. Knoll},
  journal={Proceedings of the National Academy of Sciences},
  year={2008},
  volume={105},
  pages={9897 - 9902}
}
Molecular clocks suggest that animals originated well before they first appear as macroscopic fossils, but geologic tests of these hypotheses have been elusive. A rare steroid hydrocarbon, 24-isopropylcholestane, has been hypothesized to be a biomarker for sponges or their immediate ancestors because of its relatively high abundance in pre-Ediacaran to Early Cambrian sedimentary rocks and oils. Biolipid precursors of this sterane have been reported to be prominent in several demosponges… 

Figures and Tables from this paper

Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals

This work reports a new fossil sterane biomarker that co-occurs with 24-ipc in a suite of late Neoproterozoic–Cambrian sedimentary rocks and oils, which possesses a rare hydrocarbon skeleton that is uniquely found within extant demosponge taxa.

Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals

Lipid biomarkers extracted from organically preserved Ediacaran macrofossils unambiguously clarify their phylogeny, indicating that the appearance of the Ediacara biota was indeed a prelude to the Cambrian explosion of animal life.

Phylogeny and evolutionary perspective of Opisthokonta protists

The AAR gene seems to be exclusive of Excavata and Unikonts, whereas the lysA gene is present in several unrelated taxa within all major eukaryotic lineages, indicating a role for several lateral gene transfer (LGT) events.

Sterol metabolism in the filasterean Capsaspora owczarzaki has features that resemble both fungi and animals

The sterol metabolism in the filasterean Capsaspora owczarzaki, a close unicellular relative of animals that is becoming a model organism, is characterized and a differential transcriptional regulation of this metabolism across its life cycle is observed.

Phylogenomics of Sterol Synthesis: Insights into the Origin, Evolution, and Diversity of a Key Eukaryotic Feature

The hypothesis that the few bacteria that harbor homologs of the sterol pathway have likely acquired these via horizontal gene transfer from eukaryotes is supported, and a potential candidate for the elusive enzyme performing C-3 ketoreduction in land plants and probably in other eUKaryotic phyla is proposed.

Fossil steroids record the appearance of Demospongiae during the Cryogenian period

It is suggested that shallow shelf waters in some late Cryogenian ocean basins contained dissolved oxygen in concentrations sufficient to support basal metazoan life at least 100 Myr before the rapid diversification of bilaterians during the Cambrian explosion.

Sterol Synthesis in Diverse Bacteria

The data indicate thatacterial sterol synthesis likely occurs in diverse organisms and environments and also provides evidence that there are as yet uncultured groups of bacterial sterol producers.

A basin redox transect at the dawn of animal life

Tracking the sterol biosynthesis pathway of the diatom Phaeodactylum tricornutum.

A peculiar, chimeric organization of the diatom sterol biosynthesis pathway is revealed, which possesses features of both plant and fungal pathways and underscores the metabolic plasticity of diatoms and offers important insights for the engineering of di atoms for sustainable production of biofuels and high-value chemicals.

Where's the glass? Biomarkers, molecular clocks, and microRNAs suggest a 200‐Myr missing Precambrian fossil record of siliceous sponge spicules

It is shown that demosponges are monophyletic, and that hexactinellids are their sister group (together forming the Silicea), suggesting the presence of a significant gap in the silicean spicule fossil record.
...

References

SHOWING 1-10 OF 58 REFERENCES

Poriferan paraphyly and its implications for Precambrian palaeobiology

It is demonstrated, in accordance with previous molecular studies, that sponges are paraphyletic, and that calcisponge are more closely related to eumetazoans than they are to demosponges.

A phylogenomic investigation into the origin of metazoa.

It is shown that the choanoflagellates are the closest relatives of the Metazoa, followed by the Capsaspora and Ichthyosporea lineages, although the branching order between the latter 2 groups remains unclear.

Phylogenetic and biochemical evidence for sterol synthesis in the bacterium Gemmata obscuriglobus

The primitive sterols produced by Gemmata suggest that this genus could retain the most ancient remnants of the sterol biosynthetic pathway, which was exchanged between bacteria and early eukaryotes via lateral gene transfer or endosymbiotic events.

Constraining the timing of basal metazoan radiation using molecular biomarkers and U-Pb isotope dating

THE EDIACARA BIOTA: Neoproterozoic Origin of Animals and Their Ecosystems

Present evidence suggests that the Ediacara biota included a mixture of stem- and crown-group radial animals, stem-group bilaterian animals, “failed experiments” in animal evolution, and perhaps representatives of other eukaryotic kingdoms.

On the molecular phylogeny of sponges (Porifera)

While molecular phylogenies of hexactinellids corroborate previous morphological hypotheses, phylogenetic hypotheses based on rDNA sequence analyses in Calcarea largely conflict with the previous, typological classifications.

The genome of the choanoflagellate Monosiga brevicollis and the origin of metazoans

It is shown that the physical linkages among protein domains often differ between M. brevicollis and metazoans, suggesting that abundant domain shuffling followed the separation of the choanoflagellate and metazoan lineages.

Doushantuo embryos preserved inside diapause egg cysts

The discovery of embryo-like Doushantuo fossils inside large, highly ornamented organic vesicles (acritarchs) indicates that these organisms were eukaryotic, and most probably early cleavage stage embryos preserved within diapause egg cysts.

Estimating metazoan divergence times with a molecular clock.

The last common ancestor of bilaterians arose somewhere between 573 and 656 Ma, depending on the value assigned to the parameter scaling molecular substitution rate heterogeneity, and this results support the view that the Cambrian explosion reflects, in part, the diversification of bilateralian phyla.
...