Sunday, 5 July 2015

Mistletoe Shoots Creationism in its Achilles Heel

Mistletoe species lacks genes found in all other complex organisms -- ScienceDaily

Creationism and the Intelligent Design hoax require a simple narrative to appeal to simple people who know little of science, have no intention of learning any and who believe their ignorant intuition is the best available measure of reality.

For the creation industry, this narrative includes the simplistic notion that the scientific theory of evolution states that all evolution involves increasing complexity brought about by mutation in functional genes.

This allows creationist frauds to sell the idea that evolution is impossible because a mutation will always be harmful and involve loss of function and that increased complexity is ruled out by some misrepresented version of the Second Law of Thermodynamic, which creationist dupes can be relied on to be impressed by because it makes it seem that creationism is scientific and that they understand fundamental things like the Laws of Thermodynamics.

This also explains why, when you know some basic biology, you can read a creationist article and wonder what on Earth its about, the biology and general science being almost unrecognisable sometimes barely even being parodies of the real thing.

This is also why creationists run a mile at the mere mention of parasitism and often start gibbering nonsense about Adam and Eve and 'sin' and quoting Bible verses to make it go away. Parasites of course, not only raise questions about why an omnibenevolent creator would create them. It's easy to present the supposed creation of an apex predator like humans as the act of a benevolent creator who made everything else for us; it's quite another to explain why it created parasites which have no utility value for anything other than themselves and which don't even impact on humans in any way.

The other frightening thing about parasites for creationists is that their evolution has almost invariably involved a loss of complexity, often, in extreme cases, a stripping down to the barest essentials for replicating their genome.

One such example is the mitochondrion, an integral part of all eukaryotic cells. Mitochondria are the degenerate remains of former bacteria which evolved the ability to release the energy in glucose and bind it up into a form which can be used to power other metabolic processes. At some point in the evolution of complex cells, these bacteria became first endoparasites, then endosymbionts of other prokaryotic cells and so gave rise to the first prokaryotic cells.

But this article isn't about mitochondria as such but about a specific mitochondrium found in another parasite - a species of mistletoe. Mistletoes are of course themselves parasites on other plants.

Mistletoe has long been regarded as a mystery plant and is still banned from Anglican churches because of its association with pre-Christian religions. Because it had supposed magical powers, it was used to kill the Greek demi-god Achilles who had been protected by being dipped in the magical river styx by his mother who held him by his heal, so leaving an unprotected area. He was also protected by a spell which meant he could not be killed by anything which came from the ground (i.e. everything apart from mistletoe which grows on other plants). So, he was killed by a spear made of mistletoe (or an arrow -accounts vary) striking him in the heel.

But it's not for this magical reputation that mistletoe is such an embarrassment for creationism which prefers a different set of myths, not one with lots of gods, some of whom have gods for mothers and can be killed.

Scientists investigating the mitochondrial genome (the mitogenome) of parasitic plants have made an astonishing discovery which should, if they could bring themselves to face up to it, be giving cold sweats to those creationist frauds who are currently earning their living peddling disinformation to their credulous dupes.

The mitochondria found in this species of mistletoe, Viscum scurruloideum, have degenerated to the point at which they don't even have the genes needed to carry out the normal functions of a mitochondrium. Presently, it's something of a mystery just how these essential functions are carried out, if indeed they are carried out in the mistletoe at all, rather than the host on which this mistletoe lives. What we could be seeing here is not only an extreme form of degenerate evolution in the mitochondria but also in the mistletoe, as 'superfluous' functions are lost because they are provided by the host plant.

The mitochondrial genomes of flowering plants are characterized by an extreme and often perplexing diversity in size, organization, and mutation rate, but their primary genetic function, in respiration, is extremely well conserved. Here we present the mitochondrial genome of an aerobic parasitic plant, the mistletoe Viscum scurruloideum. This genome is miniaturized, shows clear signs of rapid and degenerative evolution, and lacks all genes for complex I of the respiratory electron-transfer chain. To our knowledge, this is the first report of the loss of this key respiratory complex in any multicellular eukaryote. The Viscum mitochondrial genome has taken a unique overall tack in evolution that, to some extent, likely reflects the progression of a specialized parasitic lifestyle.

Despite the enormous diversity among parasitic angiosperms in form and structure, life-history strategies, and plastid genomes, little is known about the diversity of their mitogenomes. We report the sequence of the wonderfully bizarre mitogenome of the hemiparasitic aerial mistletoe Viscum scurruloideum. This genome is only 66 kb in size, making it the smallest known angiosperm mitogenome by a factor of more than three and the smallest land plant mitogenome. Accompanying this size reduction is exceptional reduction of gene content. Much of this reduction arises from the unexpected loss of respiratory complex I (NADH dehydrogenase), universally present in all 300+ other angiosperms examined, where it is encoded by nine mitochondrial and many nuclear nad genes. Loss of complex I in a multicellular organism is unprecedented. We explore the potential relationship between this loss in Viscum and its parasitic lifestyle. Despite its small size, the Viscum mitogenome is unusually rich in recombinationally active repeats, possessing unparalleled levels of predicted sublimons resulting from recombination across short repeats. Many mitochondrial gene products exhibit extraordinary levels of divergence in Viscum, indicative of highly relaxed if not positive selection. In addition, all Viscum mitochondrial protein genes have experienced a dramatic acceleration in synonymous substitution rates, consistent with the hypothesis of genomic streamlining in response to a high mutation rate but completely opposite to the pattern seen for the high-rate but enormous mitogenomes of Silene. In sum, the Viscum mitogenome possesses a unique constellation of extremely unusual features, a subset of which may be related to its parasitic lifestyle.

Elizabeth Skippingtona, Todd J. Barkmanb, Danny W. Ricea, and Jeffrey D. Palmera.
Miniaturized mitogenome of the parasitic plant Viscum scurruloideum is extremely divergent and dynamic and has lost all nad genes.
PNAS, 2015 DOI: 10.1073/pnas.1504491112

So, contrary to the essential creationist narrative of the ToE requiring ever-increasing complexity caused by mutation, the mitogenome in this mistletoe has degenerated beyond anything previously seen in the plant world even to the loss of essential functions. It could also be that the mistletoe has discarded this basic function itself and depends on its host for it.

And skulking in the background in all of this, for any ID proponents who haven't scuttled off for fear of what they're going to read next, there is the question of why on Earth an intelligent designer should have designed an entirely new way of performing a basic function which works perfectly well in other cells, and then made it look like this had evolved by degenerative evolution.

Any takers, or is it to be denialism yet again?

[Update] It seems there is no formal ban on mistletoe in Anglican churches although there is popularly assumed to be one.

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  1. I'm always interested in the historical and cultural clashes between religions but I can't find anything to back up the Anglican church banning mistletoe. I did find a church include it in their wreath guidelines but they are American and maybe don't care so much Do you have any references for this ban, either formal or informal?

    1. You could be right that there is no formal ban. In fact, a quick Google search shows this seems to be a popular myth which may have its origins in earlier rivalry between Christian and pagan religions.

  2. Great article. I didn't know that the mistletoe is a parasite. Thanks for the biology lesson.


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