Durham: Photosynthesis biohacking FTW


“Would you like to play a game?” — WarGames

Remember Matthew Broderick’s star turn as a hacker? Eager to play a pre-release video game, he unwittingly hacks into a Department of Defense supercomputer, the WOPR (pronounced “whopper”). After opting to play a friendly game of Global Thermonuclear War with the WOPR (an advanced AI with daddy issues), he finds the simulation quickly gains traction in reality. Fortunately, after running a series of simulations — all leading to mutually assured destruction — the computer learns that “the only winning move is not to play.”

That’s a fine sentiment when it comes to overdramatized Hollywood fare, but not so appropriate with the looming food security crisis.

Despite its reputation, hacking has evolved from a rebellious subculture (insert internet tough guy meme) to the mainstream. It’s routinely done in the IT field to expose security vulnerabilities. Consider the Robert Redford film Sneakers, where an eccentric bunch of reformed misfits offer their ethical hacking expertise for hire.

Food security is a troubling, high profile security breach of a different sort. And we already know perhaps the major weakness. With that foresight, what if we could hire consultants to biohack (a wordplay on the hacking genre) the foundation of plant productivity — photosynthesis?

But isn’t photosynthesis supposed to be hyper efficient? It’s a marvel of nature for sure. It’s the plant franchise. But it’s kind of an overhyped bait and switch. You think you’re getting Prius fuel economy when you’re really getting an inefficient gas guzzler. If we could perform an internal retrofit of that gas guzzler with a more efficient system, that’d make some major headway.

But first a brief refresher. No need to go into all of the technical doodads, thingamajigs, and whatchamacallits. Suffice it to say, plants are autotrophs. They make their own carbs for food.

Photosynthesis is all about 1) harvesting light energy, 2) converting that light energy to usable chemical energy, and 3) tapping that energy to make sugar from 4) carbon dioxide that trickles into the plant from open portholes on the leaf surface. The sugars are then used as needed to power metabolism or stashed away as starch.

Far from mystical arcana, it’s pretty straightforward. Downright elegant in many ways. More sugar production equals more energy to produce biomass = packing on the pounds. Yield is what we generally seek in a domesticated plant.

But here comes the gas-guzzling part. The workhorse enzyme responsible for “fixing” carbon — called Rubisco — is supposed to extract CO2 gas out of the air and make sugars. Unfortunately, Rubisco is kind of a Romeo. It has eyes for more than just CO2. Turns out it likes straight up O2.

Call it the photosynthetic vice. If the enzyme works on O2 instead of CO2, sugar isn’t made. Instead, the plant makes a useless and toxic end product. And energy has to be invested to break down, recycle, and repurpose the waste. One of the products released in the process is CO2 — an opportunity wasted (pun intended), since it’s the building block of sugars! All this energy spent on recycling duty could be directed at building bigger kernels, fruits, or leaves.

But there’s hope. A team at the University of Illinois biohacked tobacco with a more efficient recycling line. Essentially, using a new genetic schematic, they introduced a better designed system into the plant. Less waste meant substantial gains in productivity. Note that tobacco was only used to put a theory to the test. The hope is to transfer this technology to edible food crops.

A team in China took a different approach to biohacking. They developed a bypass in rice that funneled the CO2 produced post-recycling back into the photosynthetic loop, preventing it from being lost.

Another approach in rice is some “interior redecorating.” Most warm-season cereals have a special adaptation to prevent the inefficiencies of Rubisco. These are called C4 plants. This flavor of photosynthesis uses another enzyme called PEP Carboxylase. You could say this enzyme is monogamous, it only has eyes for CO2. It takes up CO2 and makes a compound with 4 carbons in its skeleton (hence the name C4). Then the compound is broken back down into a gas and concentrated into a special, CO2 enriched cellular chamber where O2 is excluded. Rubisco hangs out in this chamber. If it’s going to have a liaison, it has to be with CO2! This greatly increases efficiency and productivity.

Unfortunately, despite being a warm-season cereal, rice isn’t a C4 plant. It’s an oddball exception with “regular” inefficient physiology. There’s an ongoing push to find natural mutants that might have a C4 setup. To date, these searches haven’t borne fruit. A number of scientific teams are instead looking to biohacking to redesign the core internals of rice to fit a new C4 chassis.

Just when we thought we’ve maxed out plant productivity, physiologists tell us otherwise. Turns out we have a medley of enhancements in the pipeline. In the field of plant science — amid the backdrop of a hungry planet — the only winning move is to play!


Tim Durham’s family operates Deer Run Farm — a truck (vegetable) farm on Long Island, New York. As a columnist and agvocate, he counters heated rhetoric with sensible facts. Tim has a degree in plant medicine and is an Assistant Professor at Ferrum College in Virginia.

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