Top Emerging Tech 4/10: Precise genetic-engineering techniques

A breakthrough offers better crops with less controversy

Conventional genetic engineering has long caused controversy. Now new techniques are emerging that allow us to directly "edit" the genetic code of plants to make them, for example, more nutritious or better able to cope with a changing climate; we believe the benefits, and the precision in "editing," could allay the concerns, leading to more widespread adoption.

Currently, the genetic engineering of crops relies on the bacterium agrobacterium tumefaciens to transfer desired DNA into the target genome. The technique is proved and reliable and, despite widespread public fears, there is a consensus in the scientific community that genetically modifying organisms using this technique is no more risky than modifying them using conventional breeding. Whereas agrobacterium is useful, more precise and varied genome-editing techniques have been developed in recent years.

These include ZFNs, TALENs and, more recently, the CRISPR–Cas9 system, which evolved in bacteria as a defence mechanism against viruses. CRISPR–Cas9 uses an RNA molecule to target DNA, cutting to a known, user-selected sequence in the target genome. This capability can disable an unwanted gene or modify it in a way that is functionally indistinguishable from a natural mutation. Using "homologous recombination," CRISPR can also be used to insert new DNA sequences or even whole genes into the genome in a precise way.

Another aspect of genetic engineering that appears poised for a major advance is the use of RNA interference (RNAi) in crops. RNAi is effective against viruses and fungal pathogens and can also protect plants against insect pests, reducing the need for chemical pesticides. Viral genes have been used to protect papaya plants against the ring spot virus, for example, with no sign of resistance evolving in over a decade of use in Hawaii. RNAi may also benefit major staple-food crops, protecting wheat against stem rust, rice against blast, potato against blight and banana against fusarium wilt.

Many of these innovations will be particularly beneficial to smaller farmers in developing countries. As such, genetic engineering may become less controversial as people recognize its effectiveness at boosting the incomes and improving the diets of millions of people. In addition, more precise genome editing may allay public fears, especially if the resulting plant or animal is not considered transgenic because no foreign genetic material is introduced.

Taken together, these techniques promise to advance agricultural sustainability by reducing input use in multiple areas, from water and land to fertilizer, while also helping crops to adapt to climate change.

Source: Scientific American