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Gene genies

18 February 2010

Opening spread of Gene genies featureWild corn is sorry looking stuff. It’s hard to tell it from a weed at first glance and, as University of Cambridge plant scientist Jim Haseloff points out, that’s not a surprise. “Most crop species are weedy species that have been through selective breeding processes over the past 10,000 years,” he says.

The Earth is host to some 20,000 known edible plant species out of an estimated quarter million species in total. Of that 20,000 a mere 10 per cent are grown in any volume by farmers. And just three account for the bulk of the biomass we actually eat, says Haseloff: rice; corn; and wheat.

Genetically, there is not very much difference between wild corn and what farmers plant today, even after the revolution in yields provided by hybrid corn and other crops developed during the Green Revolution of the mid-20th Century. It may seem churlish to make this point but plants are quite inefficient at converting sunlight and carbon dioxide into the carbon skeleton needed to grow roots and leaves. RuBisCO, a protein complex that lies at the heart of the photosynthesis process, is notoriously inefficient as an enzyme, although some researchers argue that RuBisCO is about as good as it can get.

"I think I may have been one of the first people to have their picture taken with fecal matter," jokes Professor Andrew Ellington of the University of Texas at Austin. Ellington was not the model for a piece of concept art or an undergraduate prank but the willing model for an experiment that set out to demonstrate how living organisms could be made to behave like photographic film. They developed the image on a glass plate full of bacteria, reprogrammed by adding extra DNA to them.

Ellington is a little embarrassed to have his own image recorded by a landmark experiment in synthetic biology and points to one of Charles Darwin made using the same technique later on. "In the US, we actually celebrate Darwin Day because we have to. Our picture of Chuck is a kind of homage," Ellington explains, referring to the running battle between creationists and devotees of intelligent design against the "evilutionists".

You can power laptops - and, potentially cars - using hydrogen extracted from water. The trouble is that it takes a lot of electricity. A simpler way would be to do it naturally, using enzymes - proteins which catalyse reactions - and bacteria. These do exist: certain green algae and "cyanobacteria" can split water using photosynthesis to produce molecular hydrogen.

But to create a generation of cars that would run on water with some sludge in the back, we need to learn how to design our own bacteria and enzymes that can co-opt natural processes for our ends.

Natural hydrogen-producing enzymes are complex, often using metal atoms to help them work. "For many of the enzymes related to energy production, people have no idea how they are actually organised," says Giovanna Ghirlanda, a protein-design researcher at the University of Arizona. In some cases, no one knows where the metal atoms lie within the protein, she says.

Natural enzymes won't work too well in future fuel cells; they need to be modified, as the best hydrogen producers are poisoned by oxygen. "But oxygen is one of the main products of photosynthesis," says Professor Alfonso Jaramillo of the Ecole Polytechnic, near Paris.

Some researchers are trying to tweak the enzymes to make them less sensitive to oxygen, but with limited success. As a part of the EU-funded BioModularH2 project, Jaramillo's team is using a different approach: stick with the natural enzyme and engineer another set of proteins that take oxygen out of the cell before it can do any harm. These hydrogen producers are longer-term options: it may take 10 years to get to a prototype, says Jaramillo.

You can read the rest at the Guardian.