New prospects for drought resistance?
Scientists have found a new way to make plants resistant to drought, by genetically modifying them to activate drought-fighting processes in response to chemicals that are already commonly used in agriculture. Using protein engineering to alter the structure of one receptor, researchers at UC Riverside have found a way to reprogram plant responses to existing agrochemicals, with exciting prospects for widespread application. Drought has worsened worldwide, with devastating effects on crop survival as plants wither and die. Although highly contested, GM technology could help mitigate such losses. One potential option is to manipulate plants’ response to Abscisic Acid (ABA), since this important plant hormone regulates water loss, helping plants to survive in dry conditions. ABA is made in plant roots in response to soil water shortage, and moves to the leaves where it causes the closure of stomata, pores that allow water vapour to escape.
Treating crops with chemical agonists of ABA receptors could boost their drought tolerance by activating the natural ABA response; however, developing such chemicals is a lengthy and expensive process. In a novel approach, researchers at UCR genetically modified plants to sustain an ABA response on exposure to mandipropamid, a common agrochemical used to control fungal infections.
Sean Cutler and colleagues used protein engineering techniques to change the structure of ABA receptor PYRABACTIN RESISTANCE 1 (PYR1) so that it binds to mandipropamid; this binding triggered the molecular pathways involved in the ABA response in in vitro assays. The team then introduced the gene encoding the modified PYR1MANDI receptor into Arabidopsis plants to create transgenic strains in which exposure to mandipropamid selectively activated an ABA-like response. RNA sequencing methods confirmed that mandipropamid induced a full ABA response in transgenic PYR1MANDI lines, while there was no transcriptional response in wild type (non-transgenic) plants. After treatment with mandipropamid, the transgenic plants showed a massive improvement in survival when subjected to drought conditions. The PYR1MANDI genotype flourished after 11 days of water deprivation, showing a clear response to the chemical, while wild type plants withered (see image).
Cutler noted the potential of this technology for other GM applications: “we anticipate that this strategy of reprogramming plant responses using synthetic biology will allow other agrochemicals to control other useful traits – such as disease resistance or growth rates, for example.” In 2013 the world consumed more grain than it produced for the 6th year running, and food prices have since risen to a record high. With a global hunger crisis, grain shortages and increasingly unfavourable climatic conditions threatening crop production, can we afford to ignore GM technologies any longer?
Sang-Youl Park, Francis C. Peterson, Assaf Mosquna, Jin Yao, Brian F. Volkman and Sean R. Cutler (2015) Agrochemical control of plant water use using engineered abscisic acid receptors. Nature DOI: 10.1038/nature14123
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