The amazing diversity, beauty, and enigmatic genome of Diatoms
Diatoms are one of the most important lifeforms on the planet. Plankton are responsible for 50% of earth’s oxygen. They have a very efficient way to dissipate excess solar energy, known as non-photochemical quenching. The real distinguishing feature of the diatoms is their shells. The valves are heavily embedded with silica (up to 71%). This glass-like wall reflects light creating intricate patterns that are striking and beautiful.
Chris Bowler from the Ecole Normale Supérieure at Paris thinks this clash of concepts just represents our anthropocentric and simplistic world view. “While we might want to call diatoms ‘plantimals,’ these things are much more complex than we think,” he says.
Diatoms have a sophisticated calcium and nitric oxide-based surveillance system for monitoring environmental stresses that can detect the release of aldehydes by its wounded neighbours. 18 Diatoms appear to have a highly mosaic genome, with genes originating from many different sources. Most notably, a large fraction of the genes may have been acquired by horizontal gene transfer (HGT) from bacteria. Although genomic data have shown that HGT — the swapping of genes between species that don’t reproduce with one another — is much more common in eukaryotes than once thought, gene transfer between such distant relatives (diatoms and bacteria last shared a common ancestor a few billion years ago) is rare.
Unless there was no common ancestor of the two.
Researchers at University of Gothenburg have found diatom spores buried in seafloor sediments that were able to revive after more than 100 years in a state of suspended animation.
Diatoms detect and respond to physicochemical changes in their environment using sophisticated perception systems.
At the end of a diatom bloom, massive cell loss usually occurs. In addition to sedimentation and grazing by herbivores, programmed cell death (PCD) of stressed cells is also considered one of the major causes for the decline of algal blooms. 8 The process of PCD executed by a superfamily of cysteine aspartate-specific proteinases (caspases) is a conserved mechanism of cell suicide.
Caspases are the principal proteases that are activated during animal apoptosis and mediate cleavage of a variety of proteins ultimately leading to cell disintegration 6 Caspases have undergone remarkable proliferation and specialization in vertebrates, in which they function in a cascade including several cleavage events. Structural comparisons showed that caspases belong to a distinct class of cysteine proteases, which also includes hemoglobinases, gingipains and clostripains (hereinafter CHF-class, after Caspase-Hemoglobinase Fold). Recent studies that involved a combination of in-depth sequence analysis, structural analysis and direct experiments revealed a substantially greater diversity of caspase-related proteases than previously suspected. In particular, two families of predicted CHF-proteases that are more closely related to the classic caspases than to other proteases of this class, designated paracaspases and metacaspases, were identified
If Darwins survival of the fittest is the goal of evolution, cell suicide is counter-intuitive, and it would make no sense for cells to emerge with proteins specifically with the function to trigger suicide.
If caspases are evolutionarily conserved, it means there was no evolution, but stasis. Conservation is not evolution. its actually the oposit of evolution. Its common parlance that evoution is inserted even where it does not belong. Caspases have to emerge fully setup and functional. (Undoubtedly, similar mechanisms go back even further; scientists just happened to study this mechanism in a favorite lab worm, C. elegans.) There are at least seven genes involved in apoptosis. Failure of apoptotis has serious consequences for inflammation and autoimmunity.
By Otangelo Grasso