Arcadia Biosciences has developed rice that uses nitrogen more efficiently, so the plants need less fertilizer. As described in the Guardian article Biotech firm plans to fund GM rice crops with carbon credits yesterday, Arcadia “is working with the Chinese government to reward farmers in China that grow the firm’s genetically modified (GM) rice, with carbon credits that they can sell for cash.”
The rice will reduce fertilizer run off (responsible for oceanic dead zones) and decrease emissions of nitrogen oxide. How does it work? Arcadia’s website isn’t telling all, but I was able to find a paper in the Canadian Journal of Botany: Engineering nitrogen use efficiency with alanine aminotransferase. See the abstract below:
Nitrogen (N) is the most important factor limiting crop productivity worldwide. The ability of plants to acquire N from applied fertilizers is one of the critical steps limiting the efficient use of nitrogen. To improve N use efficiency, genetically modified plants that overexpress alanine aminotransferase (AlaAT) were engineered by introducing a barley AlaAT cDNA driven by a canola root specific promoter (btg26). Compared with wild-type canola, transgenic plants had increased biomass and seed yield both in the laboratory and field under low N conditions, whereas no differences were observed under high N.The transgenics also had increased nitrate influx. These changes resulted in a 40% decrease in the amount of applied nitrogen fertilizer required under field conditions to achieve yields equivalent to wild-type plants.
The first thing I like about their strategy is that they are using a root specific promoter. Plants only absorb nitrogen (N) from their roots, so don’t need N uptake enzymes in other tissues. Even better, the promoter is from the species being transformed so it will presumably work more effectively than a foreign promoter. The researchers chose a barley gene instead of simply using the corresponding rice gene, but there may be a reason that I don’t know about. The protein produced by the gene is one that is native to rice, however, so it is a little closer to cisgenic than transgenic (when compared to bacterial genes and such).
“Alanine aminotransferase (AlaAT) catalyses the reversible transfer of an amino group from glutamate to pyruvate to form 2-oxoglutarate and alanine.” The enzyme is present in virtually all organisms. In plants, AlaAT causes the breakdown of alanine during times of hypoxia (oxygen shortage). “Therefore, AlaAT appears to be crucial for the rapid conversion of alanine to pyruvate during recovery from low-oxygen stress.” [Miyashita et. al.]
So, it sounds like the engineered plants are able to absorb N at a higher rate, and that N goes on along normal pathways to create proteins – resulting in increased yield despite low N concentrations in the soil.
I don’t think I have to go into all of the benefits of using less fertilizer here – but there are many. In short, it will save farmers money while being a huge boon for the environment, and producing more food for growing human populations.
Good, A., Johnson, S., De Pauw, M., Carroll, R., Savidov, N., Vidmar, J., Lu, Z., Taylor, G., & Stroeher, V. (2007). Engineering nitrogen use efficiency with alanine aminotransferase Canadian Journal of Botany, 85 (3), 252-262 DOI: 10.1139/B07-019
Miyashita Y, Dolferus R, Ismond KP, & Good AG (2007). Alanine aminotransferase catalyses the breakdown of alanine after hypoxia in Arabidopsis thaliana. The Plant journal : for cell and molecular biology, 49 (6), 1108-21 PMID: 17319845
Again, thank you for posting your remarks on the Grist website and thank you for posting this thoughtful response on your own website. I hope individuals who oppose GMOs pause to read the information you are providing.
It is very important that informed scientists like you calmly respond to the criticisms of GMOs. In this one post, you demonstrate that GMOs can (1) decrease the use of chemicals, (2) lower the cost of growing food, (3) substanially reduce harm to our environment, (4) do not necessarily contain genes from frogs, and (5) can contain genes for proteins we already consume or are at least found in plants we consume.
Organizations that oppose GMOs generate a lot of noise, but little thoughtful discussion. Please continue your effort to ensure people are fully informed.
Regarding the specific GMO being discussed, I knew nitrogenous fertilzer accounted for a substantial portion of production costs, but I did not realize it could be as high as 40% of costs. It is clear that plants that can utilize nitrogen more efficiently will not only reduce direct harm to our environment but also help smaller farmers and subsitence farmers survive. This dispells the myth that GMOs raise costs and harm small farmers.
Another matter, which I’ve had trouble finding numbers for, is that a significant fraction of the greenhouse gases emitted by agricultural activity are a by-product of nitrogenous fertilzer manufacturing. Thus, additional GMOs patterned after the GM rice could substantially reduce such emissions by reducing the need for fertilizer. Have you encountered any numbers for this?
John, thanks for your thoughtful comments and words of encouragement!
If all crops had improved nitrogen efficiency, as described in this post – nitrogen fertilizer would be applied at much smaller rates, but this would probably not eliminate the need for fertilizer altogether. As far as I know, most soils can only sustain a few years of farming before yields are reduced by lack of nitrogen. The exciting thing about these plants is that they actually use the nitrogen that is applied – so smaller amounts of fertilizer results in higher yields, without harming the environment.
I have to admit that I am very excited about this one. I’d like to see the researchers find the appropriate AlaAT gene from each major crop and engineer premium nitrogen efficient lines for each (keeping them cisgenic). There is no reason why we shouldn’t see these replacing standard lines within a few years. The science is fairly easy, but as usual, patents and regulations will likely slow things down. I am really optimistic about China’s response though. I’ll post about their response as soon as I find out about it.
Sorry, I didn’t address part of your comment. Reducing the need for fertilizer will certainly reduce the amount of greenhouse gases caused by fertilizer production. I think those benefits would be overshadowed by the decrease in nitrous oxide released during and after fertilization.
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