Major crop gene breakthrough can increase photosynthesis

With projections of 9.5 billion people by 2050, humankind faces the challenge of feeding modern diets to additional mouths while using the same amounts of water, fertilizer and arable land as today. Cornell researchers have taken a leap toward meeting those needs by discovering a gene that could lead to new varieties of staple crops with 50 percent higher yields.

The gene, called Scarecrow, is the first discovered to control a special leaf structure, known as Kranz anatomy, which leads to more efficient photosynthesis. Plants photosynthesize using one of two methods: C3, a less efficient, ancient method found in most plants, including wheat and rice; and C4, a more efficient adaptation employed by grasses, maize, sorghum and sugarcane that is better suited to drought, intense sunlight, heat and low nitrogen…

The finding “provides a clue as to how this whole anatomical key is regulated,” said Robert Turgeon. “There’s still a lot to be learned, but now the barn door is open and you are going to see people working on this Scarecrow pathway.” The promise of transferring C4 mechanisms into C3 plants has been fervently pursued and funded on a global scale for decades, he added.

If C4 photosynthesis is successfully transferred to C3 plants through genetic engineering, farmers could grow wheat and rice in hotter, dryer environments with less fertilizer, while possibly increasing yields by half, the researchers said.

By looking closely at plant evolution and anatomy, Thomas Slewinski recognized that the bundle sheath cells in leaves of C4 plants were similar to endodermal cells that surrounded vascular tissue in roots and stems.

Slewinski suspected that if C4 leaves shared endodermal genes with roots and stems, the genetics that controlled those cell types may also be shared. Slewinski looked for experimental maize lines with mutant Scarecrow genes, which he knew governed endodermal cells in roots. When the researchers grew those plants, they first identified problems in the roots, then checked for abnormalities in the bundle sheath. They found that the leaves of Scarecrow mutants had abnormal and proliferated bundle sheath cells and irregular veins.

In all plants, an enzyme called RuBisCo facilitates a reaction that captures carbon dioxide from the air, the first step in producing sucrose, the energy-rich product of photosynthesis that powers the plant. But in C3 plants RuBisCo also facilitates a competing reaction with oxygen, creating a byproduct that has to be degraded, at a cost of about 30-40 percent overall efficiency. In C4 plants, carbon dioxide fixation takes place in two stages. The first step occurs in the mesophyll, and the product of this reaction is shuttled to the bundle sheath for the RuBisCo step. The RuBisCo step is very efficient because in the bundle sheath cells, the oxygen concentration is low and the carbon dioxide concentration is high. This eliminates the problem of the competing oxygen reaction, making the plant far more efficient.

Bravo. Increasing ease of food production in more difficult climates is always an achievement.

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13 comments

  1. argylesock

    I don’t agree. It’s exciting for research scientists (including some who I know personally) to increase photosynthesis in crop plants. But genetically engineered (GE, aka genetically modified, GM) crops have already had seriously bad consequences when released into the world. Superweeds and superpests have already started to appear.

    I’ve written on my own blog about GM and also about the other ways we humans can, and should, tackle hunger. I’m keeping an open mind about GM. But for now, I’m not convinced that it’s likely to be sustainable.

    So Scarecrow GM scares me. I’m going to link to this post from my own blog.

    • eideard

      Real science never scares me. And Cornell agricultural scientists are always among the top-ranked in the world. Do we need to worry about food producers and distributors? Much more.

      The most recent foodborne series of deaths in the US originated downstate here in New Mexico. Salmonella in food products from the largest producer of organic peanut butter in the country.

      It’s true of all science. The failures make the news. Successes just keep producing. Which is why, for example, the BSE-free certified beef I can buy also comes from herds sired by clones.

      I’ll stick with peer-reviewed studies.

        • eideard

          Since this was the first apparent use the studies are moving forward from here. If you wish to stay in touch with the work of the researchers at Cornell, email ksr32@cornell.edu listed as the contact at the article linked to this post.

          I already subscribe to their daily RSS feeds.

          • argylesock

            Thanks, I did look up the Cornell lab’s website. I have enough news feeds coming in but if you see anything about the Scarecrow work, addressing biosafety, I’ll be interested to know about it.

        • moss

          Google is your friend.

          I just searched for “scarecrow” gene research – and got 3,350,000 results. Almost exclusively in peer-reviewed journals.

          Enjoy. :)

            • moss

              I figure if there is a problem. say, 2 or 3 out of 3,350,000, someone will start a wordpress blog site about it. :)

              I did search “scarecrow gene biosafety” and clicked into “news” as a filter – and got zero results.

              • argylesock

                Thank you. That’s much the same as I did, in fact. I hope somebody did review the evidence about this topic – in the scientific press or anywhere else – I have access to an academic library and I’m able to understand the science. Sometimes I’m the peer who reviews in the peer review system, although my PhD was in veterinary parasitology not plant genetics.

                If I find a review about Scarecrow gene biosafety, or any other GM biosafety, I’ll post a link to it on my blog.

                • argylesock

                  I certainly appreciate the library access! Not that I use it as much as I did during my PhD but when I want to read science now, I log in through the University where I’m now a Visiting Fellow.

                  Do you get a lot out of open-access journals? I ask because since starting to blog about science, I particularly appreciate those journals for which I can link to the full text. Still, I don’t think many people read the original science unless they’re scientists. I started blogging when a Prof pointed out that I can do popsci, so now I make it my business to tell normal people what the academics are saying. And of course, to give my own opinions.

                • eideard

                  I enjoy a few. Stuff from Cornell, Purdue and Stanford come to mind – because those universities have a tradition of open communications with the wider world. They try to impress the same standards on students, professors and researchers.

  2. Pingback: Scarecrow GM scares me | Science on the Land

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