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Modified organisms

Anti-virus protection

Transgenic beans developed by Embrapa are immune to bean golden mosaic disease

SEBASTIÃO ARAUJO / EMBRAPAGenetic alterations are not active in seedsSEBASTIÃO ARAUJO / EMBRAPA

A new variety of beans, which cannot be distinguished from pinto beans – the most commonly planted variety in Brazil, and a staple food in Brazilian cuisine – has a distinct characteristic: resistance to bean golden mosaic disease, which can destroy entire plantations. The novelty lies in genetic changes introduced into the plant by agronomy engineer Francisco Aragão, of Embrapa Genetic Resources and Biotechnology (Cenargen), and agronomist Josias Faria, of Embrapa Arroz e Feijão. In September, the National Biosafety Technical Commission (CTNBio) approved the production of this transgenic bean variety, after having conducted a detailed analysis of the studies that evaluated the health and environmental risks that this plant might have posed. Hoping that CTNBio’s approval will wear down the resistance of activists, Aragão celebrates the outstanding success of work conducted at a public institution: “China is the only country to have achieved similar success so far: the Chinese now have transgenic cotton and virus-resistant papaya.”

The day after the approval, the telephone of the researcher from Cenargen never stopped ringing. Journalists were not the only callers. “Bean farmers called asking if I could send them seeds,” says Aragão, even though this is not possible yet. The bean golden mosaic virus causes damage wherever this variety of beans is planted in the Americas. In Brazil, the State of Rio Grande do Sul is the only virus-free region, because the whitefly, which transmits the virus, cannot withstand the cold. According to estimates by Embrapa Arroz e Feijão, between 9 and 18 million people could fill their plates with the beans lost to the disease.

To fight the virus, the researchers from Embrapa resorted to the beans’ natural protection: namely, RNA fragments, the simpler molecules that are kin to the DNA. This is an innate immunological system, embedded in the organism’s genetic material, and which still needs to be explored more extensively. Geneticist Marie-Anne Van Sluys, of the University of São Paulo (USP), was at a conference in the United States in 1998 during which France’s Hervé Vaucheret and Great Britain’s David Baulcombe suggested that tiny molecules moved by the plant induced an anti-virus response. “This idea attracted attention at the conference, but nobody really believed it at the time,” she says. Studies progressed throughout the years and nowadays scientists know that the tiny RNAs regulate genetic activity, acting as defense mechanisms in different organisms, such as plants, bacteria, worms and human beings. The findings in this field were awarded the Nobel Prize for Medicine in 2006, but the pioneering studies on plants were left out (see Pesquisa FAPESP nº 133).

The use of this highly complex system to study genetic functions is what drives Marie-Anne’s laboratory. “The tiny RNAs get us all mixed up,” she jokes. She explains that Aragão used anti-virus defense – one of the functions of the RNAs – which has already been widely described in medical literature. Nonetheless, demonstrating that interference by means of the RNA in transgenic beans works against the virus that causes bean golden mosaic disease led the pair of researchers from Embrapa to publish an article in Molecular Plant-Microbe Interaction in 2007 and another article in Nature Biotechnology in 2009.

In the specific case of non-transgenic beans, the plant’s natural defense mechanism is triggered only after the plant has become infected, and this is why it is frequently too late to prevent the virus’ multiplication. The researchers copied a piece of the viral genetic material into the plant’s DNA. They included the code for the small RNAs that regulate the production of the REP protein, which is essential for the multiplication of the invaders. The genetic alteration causes the transgenic plant to constantly produce these RNAs, which bend and turn into the shape of hairpins and activate a mechanism in the plant that degrades them. Thus, the plant also dismantles the RNAs produced by the virus, and aborts their dissemination.

The genetic alteration merely anticipates a process that is identical to that of the beans, with the same substances, and therefore it was not expected that such modifications posed any environmental or health hazards. With this in mind, there is no reason to worry about recent information, published by a Chinese team in the September issue of Cell Research, that the RNAs of plants eaten in higher quantities by the Chinese remain in the blood stream and regulate the expression of mammals’ genes. If this information also holds true for beans, then the beans’ anti-viral weapons are already found in human blood, with or without the transgenic beans. In addition, the team headed by Aragão verified that the mechanism is not overly active in seeds – it is more active in the plant’s green parts, which are not a common staple in the diet of the Brazilian population.

Other battles
However, genetic engineering is not enough to ensure approval of a transgenic plant. Aragão and his colleagues have been poring over this issue for nearly a decade (see Pesquisa FAPESP nº 85) and have been studying this transgenic plant since 2005: they have confirmed that nothing has changed. “We characterized the plant in molecular, agronomic and nutritional terms,” says the researcher. They have also fed the transgenic beans to animals and have not detected any differences.

In addition to reducing the mortality of pinto bean crops, the strengthening of the plant’s capacity to fight the disease on its own would greatly reduce the need for pesticides in the plantations, used to fight the whitefly. Thus, bean production would be much less hazardous to health, as well as less expensive.

Approval by CTNBio is a reason for the researchers to celebrate their achievement; however, it is not the end of the road. “We should have the seeds available for farmers within three years,” Aragão predicts, if the approval is maintained. In the opinion of Walter Colli, a professor of the Chemistry Institute at USP and president of CTNBio from 2006 to 2009, “it would be unfair for the Judicial Power to ban Embrapa’s beans. ” He explains that the Commission abides by the principle of precaution. ” Most of the Commission’s members are scientists that are thoroughly acquainted with the genetic and physiological mechanisms of live beings.”

Colli says that “the technology used by Aragão is clean, beautiful, and original.” If Embrapa’s beans go into production, then they will be the first genetically modified variety produced in Brazil without the participation of the big multinational companies.