Researchers successfully simulate photosynthesis and design a better leaf
University of Illinois researchers have built a better plant, one that produces more leaves and fruit without needing extra fertilizer. The researchers accomplished the feat using a computer model that mimics the process of evolution. Theirs is the first model to simulate every step of the photosynthetic process.
The research findings appear in the October issue of Plant 麻豆淫院iology, and will be presented today at the BIO-Asia 2007 Conference in Bangkok, Thailand.
Photosynthesis converts light energy into chemical energy in plants, algae, phytoplankton and some species of bacteria and archaea. Photosynthesis in plants involves an elaborate array of chemical reactions requiring dozens of protein enzymes and other chemical components. Most photosynthesis occurs in a plant鈥檚 leaves.
鈥淭he question we wanted to ask, was, 鈥楥an we do better than the plant, in terms of productivity?鈥� 鈥� said principal investigator Steve Long, a professor of plant biology and crop sciences at the University of Illinois.
It wasn鈥檛 feasible to tackle this question with experiments on actual plants, Long said. With more than 100 proteins involved in photosynthesis, testing one protein at a time would require an enormous investment of time and money.
鈥淏ut now that we have the photosynthetic process 鈥榠n silico,鈥� we can test all possible permutations on the supercomputer,鈥� he said.
The researchers first had to build a reliable model of photosynthesis, one that would accurately mimic the photosynthetic response to changes in the environment. This formidable task relied on the computational resources available at the National Center for Supercomputing Applications.
Xin-Guang Zhu, a research scientist at the center and in plant biology, worked with Long and Eric de Sturler, formerly a specialist in computational mathematics in computer sciences at Illinois, to realize this model.
After determining the relative abundance of each of the proteins involved in photosynthesis, the researchers created a series of linked differential equations, each mimicking a single photosynthetic step. The team tested and adjusted the model until it successfully predicted the outcome of experiments conducted on real leaves, including their dynamic response to environmental variation.
The researchers then programmed the model to randomly alter levels of individual enzymes in the photosynthetic process.
Before a crop plant, like wheat, produces grain, most of the nitrogen it takes in goes into the photosynthetic proteins of its leaves. Knowing that it was undesirable to add more nitrogen to the plants, Long said, the researchers asked a simple question: 鈥淐an we do a better job than the plant in the way this fixed amount of nitrogen is invested in the different photosynthetic proteins?鈥�
Using 鈥渆volutionary algorithms,鈥� which mimic evolution by selecting for desirable traits, the model hunted for enzymes that 鈥� if increased 鈥� would enhance plant productivity. If higher concentrations of an enzyme relative to others improved photosynthetic efficiency, the model used the results of that experiment as a parent for the next generation of tests.
This process identified several proteins that could, if present in higher concentrations relative to others, greatly enhance the productivity of the plant. The new findings are consistent with results from other researchers, who found that increases in one of these proteins in transgenic plants increased productivity.
鈥淏y rearranging the investment of nitrogen, we could almost double efficiency,鈥� Long said.
An obvious question that stems from the research is why plant productivity can be increased so much, Long said. Why haven鈥檛 plants already evolved to be as efficient as possible?
鈥淭he answer may lie in the fact that evolution selects for survival and fecundity, while we were selecting for increased productivity,鈥� he said. The changes suggested in the model might undermine the survival of a plant living in the wild, he said, 鈥渂ut our analyses suggest they will be viable in the farmer鈥檚 field.鈥�
The research was sponsored by the National Science Foundation.
Source: University of Illinois at Urbana-Champaign
