Sterol and genomic analyses validate the sponge biomarker hypothesis
Abstract
An unusual molecule is found in rocks ∼650-540 million y old, and its likely precursor, 24-isopropylcholesterol (24-ipc), is produced by some modern sea sponges. The sterane hydrocarbon analog of 24-ipc offers a potential "molecular fossil" for early animals, but certain algae also produce traces of this molecule, so it is unclear when and how frequently the ability to synthesize 24-ipc evolved. In this study, we connect 24-ipc production to a gene and conclude that algae and sponges independently evolved 24-ipc synthesis through unique gene duplication events. Although the timing of the sponge gene duplication overlaps with the geological record of the molecular fossil, the algal gene duplication occurs significantly later, supporting the connection of 24-ipc to sponges and providing the oldest evidence for animal life.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- March 2016
- DOI:
- 10.1073/pnas.1512614113
- Bibcode:
- 2016PNAS..113.2684G