Thursday, 18 September 2014

Unintelligent Design - Compensating For Evolution's Blunders

Hacked photosynthesis could boost crop yields : Nature News & Comment

You see, one of the pieces of crap design that life on Earth has had to put up with since the evolution of photosynthesis, is one of the most abundant proteins on Earth. It's an essential component of all green plants, an enzyme known chemically as ribulose-1,5-bisphosphate carboxylase/oxygenase or RuBisCo for short. I blogged about this inefficient enzyme some months ago in an article about the very many examples of unintelligent design to be found in nature. I pointed out then that the reason rubisco is so abundant is because it is so inefficient:

RuBisCo is the enzyme in photosynthesis responsible for taking carbon dioxide (CO2) from the atmosphere and building the chains of carbon in sugars which form the backbone of all organic substances.

But RuBisCo is incredibly bad at doing what it does, only carrying out about three reactions a second against tens of thousands of reactions a second for some enzymes. And it makes lots of mistakes. It finds it difficult to tell oxygen molecules (O2) from CO2 and often incorporates it by mistake, causing a chain reaction which causes a loss of carbon and wastes energy. Some plants have evolved mechanisms for reducing these mistakes but they appear to have been evolved several times independently.

Photosynthesis was one of the big steps in evolution when the cyanobacteria evolved this ability to almost literally eat the atmosphere instead of having to eat other organic substances. Some cyanobacteria then got incorporated into eukaryotic cells similarly to the way mitochondria became incorporated and so green plants were able to evolve. This gave life on Earth a huge boost in biomass but produced a toxic atmosphere containing molecular oxygen - the waste product of photosynthesis spat out from the carbon in CO2. This led to the first mass extinction until other bacteria managed to evolve ways of using all this spare oxygen.

And that's probably why RuBisCo makes its frequent mistakes. It evolved in a low oxygen environment where such mistakes were rare and insignificant but it gave its carriers such a huge advantage that the mistake has become fixed. Any tendency to change it would result in something even worse so living things have to make do with what they've got. No planning; no ability to go in reverse, and no one to stand back and think of a better way and start again. The fact that lots of plants have evolved different ways to compensate for RuBisCo's inefficiency shows that it not ideal for purpose. No omnipotent intelligent designer would come up with something which has to be compensated for.

Now a bunch of scientists led by plant geneticist Maureen Hanson of Cornell University, Ithaca, New York, USA, have stood back and thought of a better way. They are close to making a major improvement in rubisco with the potential to increase crop yields (and take some of the carbon dioxide, one of the greenhouse gases responsible for global warming, out of the atmosphere) by taking different partial solutions from the cyanobacterium Synechococcus elongatus then, to help overcome rubisco's tendency to fold wrongly, they also took a support protein from another bacteria which is thought to correct this deficiency.

However, the new improved rubisco still has an inbuilt tendency to waste energy and carbon by incorporating oxygen molecules (O2) instead of carbon dioxide (CO2) into its product which causes it to promptly disintegrate. The answer to this problem is to enclose rubisco inside a specialized structures called carboxysomes, which enclose the enzyme and create a CO2-rich environment, discouraging wasteful reactions. This is found in some photosynthetic bacteria as yet another partial work-around for rubisco's inefficiency.

When the gene for the bacterial rubisco was inserted into chloroplasts in tobacco plants (Nicotiana tabacum) in place of its normal rubisco gene, either with or without the support protein gene, both forms were able to function and converted CO2 to sugar faster than normal tobacco.

There are still some problems to overcome, especially the incorporation of it into carboxysomes, because the bacterial rubisco is also more prone to making mistakes, but they now have a useful testbed for tweaking and improving the efficiency of one of the worst examples of unintelligent design and doing what any intelligent designer would have done in the first place. This, better than almost anything, illustrates the lack of intelligence and foresight in evolution and its entirely (and inevitably) utilitarian approach to 'design' - anything which is better than than a previous version will be retained but the process can't go in reverse and so can get irretrievably stuck in an evolutionary cul-de-sac. This one occurred early in the evolution of life on Earth and so we are stuck with it - until now.

So creationists, why didn't your intelligent designer come up with a new, improved rubisco when it first designed it, and why didn't it allow for all the surplus oxygen which it would inevitably produce and which adds to its inefficiency? Could the answer be that there was no intelligence and no designer involved, maybe?

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