GENETICALLY modified plants that can kill just about any insect pest without harming beneficial insects or the environment may soon pop up in farmers鈥� fields.
The plants exploit a mechanism called RNA interference (RNAi), which organisms naturally use to switch genes off. To to this, the organism produces a double-stranded piece of RNA (dsRNA) whose sequence matches part of the gene to be silenced. Adding just a few of these to a cell shuts down the target gene.
The dsRNA produced by these modified plants targets genes specific to certain insect pests. When the pest feeds on the plant, the dsRNA it ingests shuts down some of its genes, killing it.
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This week, two teams announced that they have independently created crops that act in this way. One team in China primed plants to make dsRNA that kills the larvae of the cotton bollworm moth, which cause $1 billion of damage to cotton crops each year in China alone.
Xiao-Ya Chen and his colleagues at the Shanghai Institutes for Biological Sciences engineered tobacco and thale cress to make dsRNA that targets a gene called CYP6AE14 in the bollworm larvae. This gene usually allows the moth larvae to withstand cotton鈥檚 natural defence, a toxic chemical called gossypol. In lab tests, the larvae were first fed on the modified plants, and then munched on cotton leaves laced with gossypol (Nature Biotechnology, ). 鈥淭hey died within two days,鈥� Chen told 快猫短视频. 鈥淣ow we鈥檙e introducing the same RNA into cotton plants.鈥�
Meanwhile, Jim Roberts and his colleagues at biotech giant Monsanto in Chesterfield, Missouri, have created maize plants that produce dsRNA which protects against beetle larvae, including southern corn rootworm, the Colorado potato beetle and the western corn rootworm 鈥� 鈥渃alled the 鈥榖illion-dollar bug鈥� because of all the damage it does鈥�, says Roberts.
Roberts and his team were able to modify maize to be resistant to specific species of beetle by producing dsRNA that targets particular variants on the same gene in each species (Nature Biotechnology, ).
Both teams speculate that the dsRNA enters the insects by infecting the cells in the lining of the gut. The dsRNA infection ends up spreading to cells throughout the insects鈥� bodies. 鈥淚f the effect translates from the lab into the field, then it really could be the dawn of a new approach to pest resistance,鈥� says Peter Waterhouse of CSIRO Plant Industry, a Canberra-based agricultural branch of the Australian government鈥檚 research organisation.
Using this RNAi technique yields two clear benefits. Plants can be grown that kill specific pest species, ensuring that other beneficial species of insect 鈥� and human consumers of a crop 鈥� are unaffected. The technique could also be used to bolster other methods of killing pests. For example, Monsanto proposes adding the production of dsRNA to maize plants already modified to produce the Bt toxin 鈥� a substance usually produced by the bacterium Bacillus thuringiensis which is lethal to a wide range of insects.
鈥淭he plants can kill specific pest species while ensuring that beneficial insects 鈥� and human consumers 鈥� are unaffected鈥�
