Transgenic rice has been taught to save fertilizers

Ekaterina Rusakova, N+1

Japanese biologists have obtained genetically modified rice, in the grains of which 20 percent less phosphate compounds are stored than in ordinary plants. According to scientists, the cultivation of this rice will reduce the use of fertilizers and, at the same time, improve the digestibility of nutrients.

Phosphorus is necessary for the growth and development of living organisms. In order to increase the yield of grain crops, including rice, phosphate fertilizers are added to the fields annually. Due to their use, several problems arise. Firstly, most of the phosphates in fertilizers bind to metal ions in the soil (aluminum, calcium, iron), and plants get no more than a quarter of useful compounds. The reserves of the natural mineral phosphorite, from which fertilizers are made, are being depleted and may run out in the next 50-100 years. Another problem is that up to 85 percent of the phosphorus in grains is in the form of phytate (IP6), a compound that is not broken down in the stomach of mammals (except ruminants). It binds in the intestine with metal ions, such as iron or zinc, and prevents their absorption by the body. In addition, up to 90 percent of non-split phytate enters sewage with excrement and pollutes rivers and lakes.

IP6 is necessary for the germination of rice grains and the development of young shoots. At the same time, for the normal development of the plant, its grains may contain no more than 0.1 percent of phytate. At the same time, in most rice varieties, the concentration of this substance is at least twice as high. The authors of the new study decided to find out whether it is possible to redistribute phosphorus from grains into stems and leaves of plants. In this case, more phosphorus will remain in them, and this will reduce the amount of fertilizers needed for rice cultivation. At the same time, a smaller amount of phytate in grains, on the one hand, would affect the better assimilation of trace elements such as iron and zinc, and on the other hand, would reduce pollution of water bodies.

The scientists investigated the SPDT transporter protein, which transports phosphorus compounds across the cell membrane. They studied how it behaves during the growth phase, and also constructed several mutant organisms for the SPDT protein and found out how plants with mutant transporter proteins carry phosphorus compared to plants of the "wild" type. In addition to laboratory experiments, the researchers compared the yields of transgenic and "wild" plants in the field.

Effect of SPDT phosphate transporter protein on phosphorus distribution in rice plants. In plants of the "wild" type (left), 64 percent of phosphates are stored in grains. After harvesting, the plant loses this phosphorus. In transgenic plants (right), more than half of phosphates (57 percent) remain in the stem and leaves of plants (Yamaji et al., Reducing phosphorus accumulation in rice grains with an impacted transporter in the node // Nature, 2016).

The authors of the article found that SPDT controls the redistribution of phosphorus in the tissues of rice plants during the vegetative growth phase. In plants with the "wild" type of protein, phosphates came from the roots into new, newly grown leaves, while in mutant plants phosphorus compounds were distributed over the "old" leaves. When growing transgenic plants in the field, it turned out that their yield did not change in comparison with "wild" plants. Neither the height of the plants, nor the number of shoots and panicles with grains, nor the appearance of the grains have changed. The only difference was the redistribution of phosphorus between grains and other parts of plants. If about 64 percent of phosphate compounds were accumulated in grains in the "wild" type rice, and 35 percent in other parts of the plant, then in mutant plants the bulk of phosphates (57 percent) remained in the stem and leaves, and only 43 percent of phosphates were received in grains. At the same time, the phytate concentration in the grains of transgenic plants was 25-30 percent lower than in the grains of "wild" rice. 

In the spring of this year, an official report on genetically modified (GM) agricultural crops was published in the United States. Its authors analyzed more than 900 scientific studies and came to the conclusion that GM crops are not only not harmful, but can be useful for humans. 

A month later, the Russian State Duma adopted a law banning the cultivation and breeding of GM organisms in the country. The exception is made only for scientific experiments.

Portal "Eternal youth" http://vechnayamolodost.ru  27.12.2016