It is an understatement to say that their task was daunting. There was no assurance when they started out that what they contemplated was even technologically possible, since it had never been done before. But the two men were highly motivated by the horrors of persistent vitamin A deficiency in developing countries, and they viewed their work as a calling—one from which they would not be deterred. It took almost a decade of laboratory experimentation to invent Golden Rice, but by , Potrykus, Beyer, and a group of colleagues finally succeeded.
Once they accomplished that small but powerful technological trick, the inventors naively imagined that the hard part was now behind them.
Little did they know that the most difficult tasks still lay ahead. Once they had their initial proof-of-concept rice in hand, the inventors moved swiftly to develop Golden Rice further, first to improve the product and then to make it available, for free, to poor farmers in developing countries. Zeneca later merged with the Swiss-based company Syngenta, but the terms of the original arrangement remained unchanged. On Feb. Around the same time, the Cartagena Protocol on Biosafety was making waves.
The protocol had been adopted in the year by more than nations, including members of the European Union but neither the United States nor Canada. The agreement contained one version of the precautionary principle. Exactly what that principle, which focused on avoiding unknown risks, meant in practice was not immediately clear.
It is more of an ideal, a standard of perfection to be aimed at, than a real-world guide to action or public policy. The simple transfer of seeds from one country to another became a major logistical problem. Golden Rice was unique among genetically engineered foods, and the properties that made it different also made it immune to many of the conventional criticisms of GMOs.
Golden Rice was not invented for profit, and after , when Syngenta renounced all commercial interest in the rice, it would no longer be developed for profit. The rice would benefit the poor and disadvantaged, not modern, multinational corporations. It would be given free of charge to subsistence farmers who can save seeds and plant them from one harvest to the next, without restriction or payment of fees or royalties.
The rice was not developed primarily for the benefit of farmers, as were most other GMOs that had been designed to be resistant to herbicides or pesticides. Instead, it was developed for the sole purpose of helping users: the malnourished poor suffering from vitamin A deficiency.
And Golden Rice is not a crop upon which a major genetic engineering effort conferred a relatively minor advantage such as a longer shelf life or slightly improved taste, as was true, for example, of the long-since-abandoned Flavr Savr tomato. Had Golden Rice not faced overly restrictive regulatory conditions, it could have been cultivated by rice farmers and distributed throughout some of the poorest regions of South and Southeast Asia. It would have already saved millions of lives and prevented millions of children from going blind.
Excerpted from Golden Rice. Used with permission of the publisher, Johns Hopkins University Press. Agriculture is also ravaging the climate. As large colonial-era tea plantations crumble, family-owned plots are trying to take their place and save the industry. Shusha was the key to the recent war between Azerbaijan and Armenia. Now Baku wants to turn the fabled fortress town into a resort. This redox pathway is especially important in non-green carotenoid-bearing tissues, while the photosynthetic electron transport is thought to play an analogous role in chloroplasts.
Moreover, CRTI does not form poly-cis-configured intermediates, as plant desaturases do Bartley et al. CRTI is also capable of introducing all four double bonds in one step. In all rice genetic backgrounds tested so far, complementation with these activities is not required to proceed down the pathway.
Moreover, the activity of rice LCYs is obviously not rate limiting, since lycopene does not accumulate. Thus, Golden Rice is yellow because of the activity of intrinsic rice cyclases. The first breakthrough in the development of Golden Rice was the result of a collaboration between Peter Beyer and Ingo Potrykus, and was obtained around Easter Ye et al. At the time it became evident already that only phytoene synthase and carotene desaturase CRTI were needed to get the pathway going, while lycopene cyclase was not required.
These initial experiments were carried out with a Japonica round grain rice cultivar. Later, this was also achieved in Indica long grain cultivars Hoa et al. With the proof of concept in hands, the scientists immediately proceeded to develop ways to improve the production and accumulation of carotenoids in the seed, as it was recognised that at the levels attainable at the time 1.
These efforts led to the development of what we could call the first generation of Golden Rice after the proof of concept , also known as GR1.
This version only contained the phytoene synthase Psy gene from daffodil and the carotene desaturase CrtI gene from the bacterium Pantoea ananatis previously known as Erwinia uredovora. Further, in this early version both transgenes were expressed only in the rice endosperm by placing the genes under the control of the endosperm-specific gt1 promoter.
As only two biosynthetic transgenes are required in the process, the logical approach was to identify the bottleneck of the biosynthetic pathway and fine-tune the enzymatic activities of the two gene products involved, phytoene-synthase PSY and carotene-desaturase CRTI. Fig 3: Gene construct used to generate Golden Rice. RB, T-DNA right border sequence; Glu, rice endosperm-specific glutelin promoter; CrtI, carotene desaturase from Pantoea ananas ; tpSSU, pea ribulose bis-phosphate carboxylase small subunit transit peptide for chloroplast localisation; nos, nopaline synthase terminator; Psy, phytoene synthase gene from Narcissus pseudonarcissus GR1 or Zea mays GR2 ; Ubi1, maize polyubiquitin promoter; Pmi, phosphomannose isomerase gene from E.
In multi-step biosynthetic pathways there is generally a rate-limiting step that controls the flux through the whole pathway. This can be overcome by either increasing the amount of the rate-limiting enzyme or by using one that is more active. Experimentation with PSY genes from different sources identified the maize and rice genes as the most efficient in rice grains Paine et al.
For those interested in scientific details about carotenoids, here's a scientific review that covers the mechanisms controlling 1 the first committed step in phytoene biosynthesis, 2 flux through the branch to synthesis of a- and b-carotenes and 3 metabolic feedback signalling within and between the carotenoid, MEP and ABA pathways; by Christopher Cazzonelli, published in the journal Functional Plant Biology in with permission from CSIRO Publishing.
About Contact Site map Links. The Science of Golden Rice. Several known pathways branch off at this point, forming biologically important molecules, such as abscisic acid and strigolactones Carotenoids and their derivatives include a vast number of molecules and accordingly a great number of enzymes and cofactors. The underlying science in more detail All plant tissues that accumulate high levels of carotenoids have mechanisms for carotenoid sequestration, including crystallisation, oil deposition, membrane proliferation or protein-lipid sequestration.
The image clearly shows the progress made since the proof-of-concept stage of Golden Rice. J Exp Bot Email Facebook Twitter. Abstract The quantity of genetically modified GM foods has been consistently increasing while public concern grows. For improved accessibility of PDF content, download the file to your device.
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