March 28, 2015
To feed the world, we may need to hack photosynthesis
One of the biggest challenges of the 21st century will be figuring out how to feed our rising global population. Now, some scientists are making the radical claim that growing more food won't be enough—we literally need to hack photosynthesis.
Humans have been breeding crop plants to grow faster and yield more for approximately 10,000 years. The technological developments of the mid-20th century saw rapid increases in agricultural productivity, which kicked off an era of exponential population growth. But in the past several decades, yield improvements have slowed as many crops have reached their biological limits. If we'd like to continue hastening crop growth to meet the demands of our rising population (there may be nearly 10 billion of us by mid-century), natural breeding programs might not cut it anymore.
But what if we could do something more dramatic? When it comes to squeezing calories into our crops, photosynthesis—the biochemical pathway that plants use to turn carbon dioxide into sugar—is ultimately the rate-limiting step. According to a report authored by University of Illinois plant biologist Stephen Long and colleagues, there's never been a better time to try our hand at hacking the biochemical pathway that's fed the planet for over 3 billion years:
"We now know every step in the processes that drive photosynthesis in C3 crop plants such as soybeans and C4 plants such as maize," Long said in a statement. "We have unprecedented computational resources that allow us to model every stage of photosynthesis and determine where the bottlenecks are, and advances in genetic engineering will help us augment or circumvent those steps that impede efficiency."
As Long outlines in his paper, there are a few basic approaches scientists might use to improve photosynthesis artificially. One strategy focuses on genetic engineering, or inserting useful genes from one organism into another. For instance, certain photosynthetic microbes use different pigments than our crops, allowing them to access unusual parts of the solar radiation spectrum. If we could insert pigment genes from these microbes into higher plants, we may be able to boost the amount of sunlight our crops can capture. Or, we could swap in genes that encode more efficient versions of critical enzymes, such as Rubisco. Another approach entirely would be to inject entire chloroplasts—the tiny, jellybean shaped factories where photosynthesis occurs—from a more-efficient sun machine into a less-efficient one.
Most of this research is still very preliminary, but scientists have seen some promising results so far. In the lab, Long's team has successfully inserted a handful of genes from blue-green algae into plants, boosting photosynthetic rates by up to 30 percent. Other research teams are using sophisticated computer models to study the entire photosynthetic pathway and pin down where the biochemical traffic jams occur. Such models have been able to achieve a 60 percent improvement in process efficiency, by up and down-regulating critical genes.
Of course, biohacking alone isn't going to save us from a global food crisis: Preparing for the effects of climate change and water shortages, and integrating more food production into the fabric of our cities, will also be critical steps. (As will reducing our production and consumption of meat, which is compounding most of our other environmental problems.) But it doesn't look like the idea of hacking photosynthesis is going away anytime soon, so you can add souped-up veggies, along with lab-grown burger patties and Soylent, to the list of bizarre techno-foods that may soon occupy a spot in your fridge.