Golden rice

When creating "golden rice", the task was to achieve synthesis in the edible part of the plant - the endosperm - beta-carotene, the biochemical precursor of vitamin A. In ordinary rice, beta-carotene is used in photosynthesis , therefore it is synthesized in the leaves. Two genes were used for the modification: the psy gene from Narcissus pseudonarcissus narcissus, encoding the phytoense synthase enzyme , and the crt1 gene, taken from the soil bacterium Erwinia uredovora , the expression product of which is phytoendesaturase. These genes were placed under the control of an endosperm-specific promoter , so that they are expressed only in the endosperm.

Synthesis begins with the transformation of geranylgranyl diphosphate into phytoene with the participation of phytoene synthase. Then phytoenesesaturase transforms phytoene into lycopene , and, unlike similar plant enzymes, it catalyzes several stages of this transformation at once. In the last stage, lycopene cyclase converts lycopene to carotene.

The first version of the "golden rice" was designated SGR1. Under greenhouse conditions, it produced up to 1.6 mcg / g carotenoids ^[2] , and field tests conducted in 2004 showed from 4 to 8 mcg / g ^[5] . Nevertheless, this was not enough for the practical use of rice as a source of vitamin A, so the first option is considered only a "confirmation of the idea" ^[6] . The second generation of golden rice, in which the phytoensease gene from maize was used, was able to produce up to 37 μg / g of carotenoids, including up to 31 μg / g of beta-carotene ^[7] . This means that 100–150 g of cooked rice is sufficient to satisfy 60% of the daily requirement ^[8] .

The purpose of the development of "golden rice" is to combat vitamin A deficiency, common in many developing countries , especially in Africa , South and Southeast Asia. According to WHO estimates, in 2005, about 190 million children and 19 million pregnant women in 122 countries suffered from hypovitaminosis A ^[9] . This leads every year to 1–2 million deaths, 500,000 cases of irreversible blindness and millions of xerophthalmia cases ^[10] . Since the 1990s, under the auspices of UNICEF, there has been an international program directly supplying vitamin A to children, pregnant and nursing mothers ^[11] , which has significantly reduced the incidence and mortality associated with vitamin A deficiency ^[12] . At the same time, rice is a key source of nutrition in the most deficient countries, so rice modification looks simpler and less costly (in the long run) than direct administration of a vitamin to each child or introduction of such crops to agriculture in these countries (for example, carrots , spinach and mango ), which are traditional sources of carotenoids.

Opponents of the introduction of golden rice (including the organization Greenpeace ) expressed doubts about its safety, as well as the effectiveness of its use. In particular, it was assumed that carotene may be lost during heat treatment; In addition, critics drew attention to the need for zinc intake and sufficient fat for the synthesis of vitamin A ^[13] . To answer such questions, relevant studies were conducted. So, in 2006, the University of Nebraska showed no allergic reactions to proteins - products of inserted genes ^[14] . In 2009, an experiment on volunteers showed that golden rice carotene is effectively processed into vitamin A by the human body ^[15] . Another study published in 2012 confirmed that beta-carotene from golden rice is assimilated with the same efficiency as pure beta-carotene dissolved in oil , and with greater efficiency than carotene from spinach ^[8] . In addition to these, there are concerns related to other GMOs , such as the possibility of inter-pollination with common varieties and unknown long-term effects ^[13] .

The rights to modify after the development of SGR2 went to Syngenta , but the humanitarian council of the project Golden Rice retained the right to sub-license research organizations in developing countries ^[6] . This gratuitous license includes patents owned by various biotechnology companies ^[16] and exempts farmers from licensing fees with income of less than $ 10,000 per year, and also permits the use of the grown crop for planting, but prohibits exporting it ^[6] .

As of 2014, “golden rice” was not allowed to grow anywhere. Previously it was expected that in 2013 the Philippines would give permission for cultivation, and in 2015 - Bangladesh ^[17] . However, field tests conducted in the Philippines, which included crossing with local varieties (the initial modification was performed on one of the American varieties and requires transfer to local varieties) showed reduced yields compared to the latter, presumably due to the poorly chosen line ^{[18] [19]} . Therefore, the tests are continued using other insertion sites of the target genetic sequence (insertion events) ^[19] .

In addition to technical and legislative difficulties, the introduction of "golden rice" is faced with open opposition. For example, in August 2013, a group of Filipino radical activists ravaged one of the experimental fields ^[20] . Against the "golden rice" continues to actively advocate Greenpeace ^[21] . In 2016, more than a hundred Nobel laureates signed an open letter urging Greenpeace to end the campaign against genetically modified organisms in general and golden rice in particular ^[22] . However, an earlier study in 2016 showed that the activities of environmental organizations do not have a significant impact on the development. Although the activists did ruin the experimental field, it was one of many areas where research is continuing, far from complete ^[4] . Greenpeace spokeswoman Wilhelmina Peregrina also said that golden rice was not ready, responding to the statement from Nobel laureates ^[23] .

• Safety studies of genetically modified organisms

• Golden Rice Project (eng.)