It’s been nearly two years since a group of Nobel laureates published a letter supporting “Precision Agriculture (GMOs)” and, more specifically, Golden Rice, the genetic engineering project first embarked upon in the mid-1990’s to “reduce or eliminate much of the death and disease caused by a vitamin A deficiency (VAD), which has the greatest impact on the poorest people in Africa and Southeast Asia.” And although Golden Rice with its potential benefit is still not available to people suffering from VAD, a couple of significant technical and other events in the project’s development have occurred over the last couple of years that showcase some of the imprecision and potential risks inherent in the technology used to create this genetically engineered (GE) rice.
The potential benefit of Golden Rice has yet to be realized
The prospect of reducing or eliminating much of the death and disease caused by VAD is certainly an intended potential benefit of Golden Rice. But before that potential benefit might be realized, there are still many issues that remain to be addressed.
For one thing, we still don’t know whether Golden Rice will be effective in treating VAD. According to the International Rice Research Institute (IRRI), the organization developing Golden Rice “for cultivation and use in human food in certain south and southeast Asian countries,” “bioefficacy studies to determine the effect of Golden Rice consumption on various measures of vitamin A status” in humans still need to be carried out, and “appropriate regulatory authorization and institutional review board clearances” for such studies have not been obtained as of yet.
Additionally, regulatory “authorization for the unconfined environmental release of GR2E Golden Rice” and the “use of GR2E Golden Rice in food and feed, or for processing,” in the Philippines or any other country in Asia, Africa and Latin America where VAD is a serious problem, has not yet been obtained.
On the other hand, IRRI has received what it refers to as a “positive food safety evaluation” of Golden Rice GR2E from the US FDA (as well as from Food Standards Australia New Zealand and Health Canada). The short letter from FDA conveying this “positive food safety evaluation” is odd for several reasons, first just as an example of how voluntary consultation about newly developed GMOs works at that US agency. The safety-related content in FDA’s letter to IRRI is comprised primarily of “information IRRI has provided” and conclusions “it is [FDA’s] understanding” IRRI has reached. Non-administrative, safety-related FDA input is limited to the agency’s usual consultation-closing statement: “Based on the information IRRI has presented to FDA, we have no further questions concerning human or animal food derived from GR2E rice at this time. However, as you are aware, it is IRRI’s continuing responsibility to ensure that foods marketed by the firm are safe, wholesome, and in compliance with all applicable legal and regulatory requirements.” (One can see why IRRI does not refer to FDA’s position on Golden Rice as an “approval.”)
Another odd thing is that IRRI informed FDA that “GR2E rice is not currently intended for cultivation or marketing in the United States.” Which begs the question: why, since “according to IRRI, GR2E rice is intended for cultivation and use in human food in certain south and southeast Asian countries…for populations in which vitamin A deficiency is common,” did IRRI go through the “regulatory” process with the US FDA in the first place? IRRI’s answer? “…GR2E rice, or human and animal food products derived from GR2E rice, may enter the U.S. food supply via imports from countries of production.” It’s not clear whether IRRI means that the US may knowingly import Golden Rice or that its non-GMO rice imports might be contaminated with Golden Rice or both; perhaps IRRI is just trying to cover all its bets. In any case, this possibility of Golden Rice being imported into the US explains why 3 of the 6 paragraphs in FDA’s “consultation closure letter” to IRRI deal with the issue of GMO labeling.
The most striking point made in the FDA letter, however, is that the “concentration of β-carotene in GR2E rice is too low to warrant a nutrient content claim.” The whole idea of Golden Rice is to provide a necessary dietary nutrient to people at risk of, or suffering from, vitamin A deficiency…and the levels are too low to warrant a nutrient content claim with FDA?
The explanation of this paradox lies partly in the amounts of rice that Americans versus Filipinos (for example) consume. According to IRRI, to meet the FDA requirement for a nutrient claim “10 percent or more of the recommended daily intake (RDI) for vitamin A must be present as beta-carotene” in the 45 grams of rice that Americans, on average, consume daily; and the amount of beta-carotene in Golden Rice is less than that. (If the 10% threshold had been reached, I believe premarket review and/or official approval by FDA would have been required.) But the average Filipino consumes more than 6 times that much rice, and IRRI expects that if all of that was Golden Rice, “30-50% of the estimated average requirement for vitamin A” could be met in the “subgroups at highest risk of vitamin A deficiency.”
The imprecision of genetic engineering and its effects on Golden Rice
But another reason why the concentration of beta-carotene in today’s Golden Rice is relatively low (~7.31 micrograms/gram, ~10% of the level found naturally in carrots-from safety assessment documents submitted to the government of the Philippines) is that what had been the most advanced variety of Golden Rice in IRRI’s product development pipeline, a variety with substantially higher levels of beta-carotene, GR2-R1, turned out to be a genetically engineered mutant with no market potential.
GR2-R1 had been a very promising Golden Rice “event,” with levels of beta-carotene more than twice as high those in GR2E (Paine et al. 2005). It was so promising that it was being bred into a popular rice variety called Swarna in preparation for its use by farmers in India. But the plants produced as a result of this breeding effort turned out to be stunted, pale green and have drastically low yields. To determine what was causing these problems a group of scientists in New Delhi (Bollinedi et al. 2017) carried out a molecular characterization of GR2-R1 that revealed that the foreign genes responsible for production of beta-carotene in GR2-R1 rice grains had been inserted into a rice gene called OsAux1, mutating it. The protein product encoded by this gene provides for proper function of a master growth regulator (auxin) in rice that is “involved in every aspect of plant growth and development” (Bollinedi et al. and references therein); mutating it in GR2-R1 rice caused various abnormalities in plant growth and development.
I am not at all surprised that the genetic engineering process caused this mutation. After all, we’ve known for more than 25 years that the Agrobacterium-based methods of genetic engineering cause frequent insertional mutations in recipient plants; Bollinedi et al. (2017, and references cited therein) state that 35-58% of insertions of foreign DNA sequences disrupt recipient plant genes.
What I am surprised about is that no one had (apparently) ever checked to make sure that this GE rice plant did not contain such a GE mutation prior to it being readied for farmers’ fields. Genetic engineering and associated technologies provide genetic engineers with the ability to identify such insertional mutations. Genetic engineers should be doing so early in the development of products intended for commercial release and eliminating any identified mutants from their product development pipelines. And regulatory agencies should ensure that developers of GMOs have carried out this necessary, straightforward screen of potential products.
Another source of abnormalities in GR2-R1 rice related to genetic engineering
Bollinedi et al. (2017) identified an additional problem with GR2-R1 rice, a problem that could affect other GR2 Golden Rice events as well, like the GR2E rice being readied for commercial release.
The foreign genes responsible for increasing levels of beta-carotene in all of the GR2 “events” of Golden Rice are meant to be expressed only in rice grains because expressing them in other parts of the plant could unintendedly disturb other biochemical pathways that share a common substrate, such as those involved in the biosynthesis of chlorophyll or various plant growth regulators. To accomplish this specificity, genetic engineers at Syngenta (Paine et al. 2005) spliced the “promoter” region of a rice gene called Glutelin I, which is only expressed in grain (the promoter is responsible for turning a gene on or off), to the protein-coding regions of the genes involved in beta-carotene synthesis that they wanted to insert into rice plants; then they inserted the resulting chimeric genes into rice plants via genetic engineering.
But in characterizing the abnormal GR2-R1 Golden Rice plants (produced by Syngenta as mentioned above), Bollinedi et al. found that expression of the foreign chimeric genes was not grain-specific as had been intended, the foreign genes were expressed in leaves as well. These scientists hypothesized that this “leaky” expression of the chimeric foreign genes was responsible for the pale leaves and (some of the) growth regulator-related abnormalities in GR2-R1 rice plants (because biosynthesis of green chlorophyll pigments and expression of plant growth regulators had been disrupted due to competition with the GE enzymes for beta-carotene biosynthesis). They documented dramatic alterations in the expression of four key plant growth regulator genes in support of their hypothesis.
The future of Golden Rice
In light of these problems with GR2-R1 Golden Rice that are related to the process of genetic engineering, IRRI is now concentrating on developing GR2E Golden Rice for commercial release. IRRI (in conjunction with the Philippine Rice Research Institute) submitted an application for a biosafety permit for the “direct use in food, feed, or for processing of GR2E Golden Rice,” (http://irri.org/golden-rice/faqs/what-is-the-status-of-the-golden-rice-project) to the Department of Agriculture-Bureau of Plant Industry (DA-BPI) in the Philippines in early 2017. (A link to the collection of Golden Rice data files can be found on this website: http://biotech.da.gov.ph/Decision_docs_jdc_direct.php, about 2/3 of the way down the page.)
Information in the submission package appears to indicate that GR2E Golden Rice has been checked and that a mutation was not created at the site in the rice genome where the foreign genes were inserted. I’m not as convinced by the submitted data that the “leaky” endosperm promoter issue has been adequately analyzed.
I hope Golden Rice will be successful in reducing vitamin A deficiency. But we need to remember that “Precision Agriculture (GMOs)” is not as precise as some would have you believe. There is a lesson to be learned from GR2-R1 Golden Rice, and it is to be more vigilant about the less precise aspects of crop genetic engineering.