Nutrition and a sufficiently rounded diet of vitamins and minerals is key to remaining healthy. This is true for every person in the world. Unfortunately, there are many, billions even, that lack critical nutrients in their diets. This is often due to a combination of poverty, location, climate, and a societal and cultural focus on only certain types of crops.
Due to this, a large focus of agricultural research has been on growing crops that are able to supply these necessary nutrients, even while the original cultivar of the crop would not include them. Biotechnology has especially focused on including these genetic nutrient pathways in staple crops that are eaten wildly in the most poverty-stricken areas.
Golden Rice Rerun
We’ve discussed this topic before on Bioscription and a lot of what is on board for today relates to the insights pointed out then. The production of Golden Rice as a new option for providing Vitamin A to those regions that lack it has been ongoing for decades, with the first version of it being released in 2000. This original cultivar, while forming the needed carotenoids, did so at too low of a level to really be helpful for uptake of Vitamin A itself.
By 2005, the researchers were able to fix this problem and released Golden Rice 2 that produces 23x the carotenoids of the original version and which is easily able to meet daily nutritional requirements of Vitamin A from just a single bowl. Since then, research on this area for rice hasn’t needed to progress much beyond tweaks to improve growth rates and yield, among other traits.
Instead, studies to produce rice rich in other nutrients has progressed, resulting in rice breeds that are high in iron and other that are high in zinc, both of which are also important nutrients in regions where rice is a part of the common dishes. But having several different rice cultivars only useful for an individual nutrient would be difficult to market and ensure the population uses all of them at once. In all likelihood, families would gravitate toward just a single variety based on their personal tastes.
Rebooting Old Versions
Now though, this may be a moot point. Researchers at Eidgenössische Technische Hochschule (ETH) Zurich, the same organization responsible for the aforementioned Golden Rice, have produced a breed that combines all of those facets. It is capable of producing iron, zinc, and precursors for beta-carotene production.
Here’s how they did it. Each different type of nutrient requires its own enzyme to progress. The first was a gene from the model organism Arabidopsis called Nicotianamine synthase 1 that helps in the synthesis of nicotianamine. This pathway takes the nicotianamine and further transforms it into a number of metal chelators able to bond with and concentrate the production of metal ions like iron and zinc.
Next the gene coding for the protein Ferritin was taken from the common bean plant and inserted into the rice. This protein is an iron storage mechanism and a single molecule of it is able to store around 4,500 iron ions. This allows for the iron made by the nicotianamine and metal chelators above to be stored for collected usage in the plant. These two parts are able to increase iron and zinc in the rice endosperm to sufficient levels.
The final procedure was the old workhorse of beta-carotene and mostly the same mechanisms were used as in Golden Rice 2. The gene for the enzyme known as Phytoene synthase that helps in the biosynthesis of carotenoids was introduced from the corn genome. For rice, this means taking the geranylgeranyl diphosphate (GGDP) that rice is already able to make and continuing its pathway breakdown. Since rice does have an immature form of the beta-carotene production pathway, but one that isn’t complete and lacks the requisite genes to finish it. This gene accomplishes that.
The very last step of the beta-carotene pathway is to take the phytoene made from GGDP by the Phytoene synthase gene above and finish its change into β-carotene. This normally requires three enzymes to accomplish, going from Phytoene to Neurosporene to Lycopene and then to the final product. However, the scientists were able to find a bacterial gene from prior Golden Rice research called Carotene desaturase that can do all three steps itself, saving a lot of effort in gene transfer and even energy within the rice’s cellular metabolism.
Still Not Perfect, But Passable
And, voila, a rice cultivar with four gene additions that make it capable of producing iron, zinc, and beta-carotene all at once. The most ingenious part of it is that all four of these genes were tied to a single genetic locus on the rice genome, meaning they only function when they work together. This synergistically increases their output.
The only downside to all of this is that iron and zinc production does reduce the overall focused output of beta-carotene by a significant amount. Rather than the incredibly high average of 31 μg/g found in Golden Rice 2, these new cultivars are only able to make about 3.4 μg/g. This is about at the level that is the minimum expected for beneficial Vitamin A uptake. Compare this to the original Golden Rice that sat at only 1.3 μg/g.
The researchers are going to continue to work at it. They would like to break 4 μg/g as a good baseline for helping populations, though the ultimate goal is between 8 and 12 μg/g, which is currently considered to be the perfect amount for daily intake and that any more is excess. For now, the intake requirements for this cultivar will have to be set for 2 bowls of rice a day, rather than just the one with Golden Rice 2.
Another Step Forward For Health
But with the other nutritional benefits from the iron and zinc included, it seems like a fair price to pay, even if the scientists are unable to increase the fortification further, as a cultivar with all three nutrients will be able to reduce health and disease issues tremendously in regions like Southeast Asia. Field tests of the cultivar will begin next year and they hope to have it available for commercial release within five years, depending on how long bureaucratic approval takes in the relevant countries.
The ability for scientists to further combine and improve crops such as these gives hope for future multivitamin combinations that will enable different regions of the world to obtain daily nutritional requirements even without having to change from their common cuisine. Especially for those too poor to buy anything other than rice or bananas as a basic staple. It is the latter group of people that is the special focus of this research and the hope that science will be able to save as many lives as it can and improve the general health of everyone.
Photo CCs: Brown rice from Wikimedia Commons
