Speed-the-Leaf: RIPE’s photosynthesis breakthru offers a 20% increase in crop yield

August 22, 2022 |

For the past couple of minutes I have been racking my brain trying to recall when I first had Steven Long on stage with me, and I first learned about RIPE, which stands for Realizing Increased Photosynthetic Efficiency and I find myself rueing that in my case it stands for Recall Is Poorly Engineered. 

Some years ago, the RIPE team went down the rabbit hole of transforming photosynthesis,”harnessing the sun to help the feed the world,” on the noble theory that if plants are more efficient, we’ll have more food, fiber, fuel, and what have you.

I’ve stood on the docks of academe and shouted God Speed! to many a team sailing toward the sun and the New World, aiming to expand PAR (photosynthetically active radiation), improve RuBisCo, and chase the transformation of photosynthesis. Generally, they returned home like the bedraggled survivors of shipwreck.

So when I waved goodbye to Steve and the team as they embarked on the good ship RIPE, I confess I waved as at passengers on the Titanic, never to be seen or heard from again. I had come to believe that photosynthetic pathways were a scientific Congo, a hopeless, one-way journey into the Heart of the Opposite of Darkness. 

Just this week, the jungle weeds parted and the team emerged from years of discovery and peril, and have reported a breakthrough that few, and certainly not myself, ever thought possible. 

Somewhere upriver in the Land of Unusual Thinking they have discovered a means of improving yields in food crops by as much as twenty percent. That’s the boost in soybeans that has been shown in their research and trials. In the physical world, 600 million years into evolution, it’s huge, like reading that New York is suddenly 20 percent farther from Washington, DC.

The earth has moved.

The science story

Let us start with remembrances of beach days past. When we start to get too much sunshine, we head indoors, because our skin responds to overexposure to ultraviolet light by turning red with painful sunburn. 

Plants have a version of the same problem, They love the sun, but not too much of it. Lacking umbrellas, when the light is heavy, they produce a protein that dissipates the energy as heat. Sort of the same as you do, when skin gets sunburned, it gives off heat.

Evolution should have made a switch mechanism that moved as fast as clouds passing overhead, or the sun changing angles and passing behind a tree and throwing shade. Plants should be able to toggle on and off rapidly. But, they can’t. It takes several minutes to throw the switch. 

Sort of like this.

PLANT BRAIN TO LEAF: Clouds coming over, restart full production mode.
LEAF: Roger that. Be ready in 5 minutes. 
BRAIN: The cloud will only be overhead for three minutes.
LEAF: 10-4, good buddy. T minus 4 minutes, 55 seconds and counting.
BRAIN: Never mind, cloud’s passed over. Stay in protective mode.
LEAF: Read you 5 x 5. T minus 4 minutes, 50 seconds and counting.
BRAIN: Never mind, leaf. Stand down.
LEAF: Lima Charlie that, brain. Glad to help.

So, you get the idea. 

But what if you could change the timing? For centuries we’ve sung God Speed the Plough at the opening of planting season, to celebrate our love of the land and our prayers for good harvest.

What if we sang God Speed the Leaf? After all, the Calvin Cycle has like 100 steps, maybe there’s a short-cut that evolution hasn’t needed before to develop.

Turns out, there is. As reported in Science, here. The RIPE team  rebuilt three genes that code for proteins of the xanthophyll cycle, which is a pigment cycle that helps in the photoprotection of the plants. 

The technology story

The researchers report:

Once in full sunlight, this cycle is activated in the leaves to protect them from damage, allowing leaves to dissipate the excess energy. However, when the leaves are shaded (by other leaves, clouds, or the sun moving in the sky) this photoprotection needs to switch off so the leaves can continue the photosynthesis process with a reserve of sunlight. It takes several minutes for the plant to switch off the protective mechanism, costing plants valuable time that could have been used for photosynthesis.

The overexpression of the three genes from the VPZ construct accelerates the process, so every time a leaf transitions from light to shade the photoprotection switches off faster. Leaves gain extra minutes of photosynthesis which, when added up throughout the entire growing season, increases the total photosynthetic rate. This research has shown that despite achieving a more than 20% increase in yield, seed quality was not impacted

They tried it in tobacco, which is a model crop for researchers, and now have replicated the results in soybeans. Additional field tests of these transgenic soybean plants are being conducted this year, with results expected in early 2023.

The impact

The team has been busy highlighting the discovery, as you might expect, as a solution to world hunger, and you understand in a flash why these good people chose genetics instead of economics — because of course food scarcity and malnutrition is a function of income inequality rather than food availability. There isn’t enough aggregate monetary demand to incentivize the conversion of all available land to food production, and small wonder, I saw a presentation last year dividing calories by population to demonstrate that we have more food per capita than ever, as a species. 

That does not diminish the achievement in science — for it has the potential to make food more affordable though it is likely simply to transfer more wealth to landowners in the form of rent driven by higher profits that higher yields produce. Good news for the landholders of Illinois who support universities through land taxes. 

What will we do with 20 percent higher yields in food crops like soybeans. I doubt we will eat more soybeans, or send food to Africa they cannot pay for. That’s why Safeway’s not there in the first place. More’s the pity. I do believe that increased supply will reduce commodity prices in the absence of increased demand, or at least beleaguered bioenergy makers and ranchers might hope for stabilized prices. That would be a good thing.

Enough about the economics. Let’s get back to our intrepid researchers and the troubled world of photosynthetic efficiency where they worked their magic.

The Bottom Line

Let’s put it plainly. If this can be achieved broadly across grains and oilseeds, this is the bomb. Hard to imagine where we’ll get a 20 percent crop yield boost off a single innovation any time in my lifetime, Never say never, but I wouldn’t  bet on it. 20 percent? That’s like food, fiber or fuel for 1.6 billion people, billion with a B. As in the Bomb. That’s like India. Wow.

Reaction from the stakeholders

“Despite higher yield, seed protein content was unchanged. This suggests some of the extra energy gained from improved photosynthesis was likely diverted to the nitrogen-fixing bacteria in the plant’s nodules,” said RIPE Director Stephen Long, Ikenberry Endowed University Chair of Crop Sciences and Plant Biology at Illinois’ Carl R. Woese Institute for Genomic Biology.

“Having now shown very substantial yield increases in both tobacco and soybean, two very different crops, suggests this has universal applicability,” said Long. “Our study shows that realizing yield improvements is strongly affected by the environment. It is critical to determine the repeatability of this result across environments and further improvements to ensure the environmental stability of the gain.”

“The major impact of this work is to open the roads for showing that we can bioengineer photosynthesis and improve yields to increase food production in major crops,” said De Souza. “It is the beginning of the confirmation that the ideas ingrained by the RIPE project are a successful means to improve yield in major food crops.”

“This has been a road of more than a quarter century for me personally,” said Long. “Starting first with a theoretical analysis of theoretical efficiency of crop photosynthesis, simulation of the complete process by high-performance computation, followed by application of optimization routines that indicated several bottlenecks in the process in our crops. Funding support over the past ten years has now allowed us to engineer alleviation of some of these indicated bottlenecks and test the products at field scale. After years of trial and tribulation, it is wonderfully rewarding to see such a spectacular result for the team.”

More about RIPE

RIPE is led by the University of Illinois in partnership with The Australian National University, Chinese Academy of Sciences, Commonwealth Scientific and Industrial Research Organisation, Lancaster University, Louisiana State University, University of California, Berkeley, University of Cambridge, University of Essex, and U.S. Department of Agriculture, Agricultural Research Service.

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