Hacking Photosynthesis

Some biologists say that by engineering a new chemical system in plants, using genes from cyanobacteria, they have greatly improved the results of photosynthesis. If so, this might turn out to be a very big deal.

One of life's key molecules is an enzyme called RuBisCO, which catalyzes the reaction that captures carbon dioxide from the atmosphere and builds sugar. RuBisCo is not a particularly efficient catalyst – one of those imperfections that in themselves constitute a powerful argument for evolution vs. design – and it sometimes catalyzes harmful reactions instead. In particular, it sometimes captures an O2 molecule instead of CO2, which creates a byproduct harmful to plants: phosphoglycolate, a two-carbon acid.

Plants of course have systems for managing this acid; in fact they have several different systems. One reason corn and sugarcane are more efficient than wheat or rice at converting sunlight to sugar is that they have a better system. Some cyanobacteria (single-celled algae) have even better systems.

So these researchers altered the genomes of tobacco plants to replace their natural, rather inefficient system with a better one from bacteria. The result are "super" tobacco plants that grow up to 40 percent faster. Tobacco was used in this study for the same reasons geneticists are always working with fruit flies, that is, they have easily manipulated chromosomes and people have a lot of experience working with them. These researchers are now trying to extend their results to food plants such as soybeans and the African cow pea.

The thing about tinkering with these fundamental reactions, of course, is that they may actually influence many different things about the plant's life; that bizarrely complicated Krebs Cycle you may have studied in biology is not efficient, but on the other hand the various intermediate products are sometimes siphoned off to serve as feed stocks for other reactions. So it may turn out that some plants depend on their crazy, inefficient photosynthetic reactions to do other things.

There are a lot of scientists studying this and related problems, so I guess we will soon see.