THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
Dear Friends and Colleagues
Detrimental Genomic Effects Found in Golden Rice Offspring
Rice (Oryza sativa L.) is one of the three major food crops of the world, vital for the survival of more than half of the world’s population. Globally about 480 million metric tons of milled rice are produced annually, 80% of which is produced on small farms, primarily to meet family needs. Developing countries in Asia are heavily reliant on rice for their dietary caloric supply, with about 90% of the world’s rice produced and consumed in China, India, Indonesia, Bangladesh, Vietnam and Japan alone.
"Golden Rice" was created by genetically engineering rice to produce provitamin A in a bid to address Vitamin A deficiency. Researchers from the Indian Council of Agricultural Research – Indian Agricultural Research Institute (ICAR-IARI) introgressed the provitamin A trait from Golden Rice 2 into a popular Indian rice variety, Swarna. The resulting plants were dwarf with pale green leaves and drastically reduced panicle size, grain number and yield as compared to the recurrent parent, Swarna (Item 1).
The researchers identified several reasons for these detrimental effects: The new gene constructs interfered with the plant’s own gene for producing growth hormones, and the additional gene constructs were not, as intended, active solely in the kernels, but also in the leaves. This led to a substantial reduction in the content of chlorophyll, which is essential for vital functions in the plants (Item 2).
These unintended effects were not detected in previous investigations and are highly relevant for the risk assessment of the plants. Once released, the transgenic plants could spread their gene constructs into populations of weedy rice as well as other cultivated varieties. In addition, genomic effects not found in the original plants can occur in plant offspring. At the stage when the hazards are identified, it can be impossible to remove the transgenes from the environment.
Some other Golden Rice lines are already known to show irregular patterns of inheritance. For example, additional changes in the metabolism of the rice kernels were described in 2016. So far, there are no Golden Rice varieties available for commercial cultivation.
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Item 1
MOLECULAR AND FUNCTIONAL CHARACTERIZATION OF GR2-R1 EVENT BASED BACKCROSS DERIVED LINES OF GOLDEN RICE IN THE GENETIC BACKGROUND OF A MEGA RICE VARIETY SWARNA
Haritha Bollinedi et al.
http://dx.doi.org/10.1371/journal.pone.0169600
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0169600
Abstract
Homozygous Golden Rice lines developed in the background of Swarna through marker assisted backcross breeding (MABB) using transgenic GR2-R1 event as a donor for the provitamin A trait have high levels of provitamin A (up to 20 ppm) but are dwarf with pale green leaves and drastically reduced panicle size, grain number and yield as compared to the recurrent parent, Swarna. In this study, we carried out detailed morphological, biochemical and molecular characterization of these lines in a quest to identify the probable reasons for their abnormal phenotype. Nucleotide blast analysis with the primer sequences used to amplify the transgene revealed that the integration of transgene disrupted the native OsAux1 gene, which codes for an auxin transmembrane transporter protein. Real time expression analysis of the transgenes (ZmPsy and CrtI) driven by endosperm-specific promoter revealed the leaky expression of the transgene in the vegetative tissues. We propose that the disruption of OsAux1 disturbed the fine balance of plant growth regulators viz., auxins, gibberellic acid and abscisic acid, leading to the abnormalities in the growth and development of the lines homozygous for the transgene. The study demonstrates the conserved roles of OsAux1 gene in rice and Arabidopsis.
Item 2
‘GOLDEN RICE’: UNEXPECTED GENOMIC EFFECTS
Testbiotech
https://www.testbiotech.org/en/node/1859
Press Release
Rice plants show reduced growth and irregular gene expression
A new publication has reported unintended effects in genetically engineered rice producing precursors of vitamin A, so-called carotenoids. Crossing the manipulated rice with the Indian variety Swarna led to a nasty surprise: The resulting plants showed extensive disturbance in their growth. The researchers identified several reasons for this: The new gene constructs interfere with the plant’s own gene for producing growth hormones, and the additional gene constructs were not, as intended, active solely in the kernels, but also in the leaves. This led to a substantial reduction in the content of chlorophyll that is essential for vital functions in the plants.
These unintended effects were not detected in previous investigations, and it was assumed that the genetically engineered plants used in these trials would show genetic stability. In fact, these detrimental genomic effects remained undetected until the transgenic plants were crossed with the variety called Swarna, which is grown widely in India.
The observed effects are highly relevant for the risk assessment of the plants. Once released, the transgenic plants could spread their gene constructs into populations of weedy rice as well as other cultivated varieties. In addition, genomic effects not found in the original plants can occur in plant offspring. At the stage when the hazards are identified, it can be impossible to remove the transgenes from the environment.
“Instead of helping people to combat malnutrition, these plants, if grown on the fields, might endanger their whole rice harvest,” Christoph Then says for Testbiotech. “It is worrying that effects that can arise from crossing genetically manipulated plants with other varieties are, as yet, not included in risk assessment.”
It is not the first time that such problems have been reported: Some other ‘Golden Rice’ lines are already known to show irregular patterns of inheritance. Furthermore, there are uncertainties regarding the biological quality and safety of the plants. For example, additional changes in the metabolism of the rice kernels were described in 2016.
So far, there are no varieties available for commercial cultivation. According to the International Rice Research Institute IRRI, the safety and usefulness of the plants for nutrition needs further investigation.
Contact: Christoph Then, info@testbiotech.org, Tel + 49 (1) 151 54638040