Scientists at the University of California, Davis, have developed wheat plants that stimulate the production of their own fertilizer, opening the path toward less air and water pollution worldwide and lower costs for farmers.
The technology was pioneered by a team led by Eduardo Blumwald, a distinguished professor in the Department of Plant Sciences. The team used the gene-editing tool CRISPR to get wheat plants to produce more of one of their own naturally occurring chemicals. When the plant releases the excess chemical into the soil, the chemical helps certain bacteria in the soil convert nitrogen from the air into a form the nearby plants can use to grow. That conversion process is called nitrogen fixation.
The study was published online in Plant Biotechnology Journal.
In developing countries, the breakthrough could be a boon for food security.
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Worldwide, wheat is the No. 2 cereal crop by yield and takes the biggest share of nitrogen fertilizer, using about 18% of the total. Globally, more than 800 million tons of fertilizer were produced in 2020 alone, according to figures from the United Nations Food and Agriculture Organization.
[Excerpts from study]
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The addition of N-fertilisers to cereal crops contributes to enhanced food production, and more inorganic N-fertiliser will be needed to support a further increased food production required to satisfy the needs of an increasing world population (Omara et al. 2019). These additional inputs of N-fertilisers would make grain production more expensive, with a considerable aggravation in environmental pollution. Thus, there is a growing need to develop sustainable alternative agricultural practices aimed at reducing the excessive use of inorganic N-fertilisers.
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A synthetic biology approach was used to create a plant-bacteria signalling circuit to improve N-fixation activity of bacteria associated with the roots of a target plant. Barley was engineered to produce scyllo-inosamine (SI), a rhizopine signalling molecule, and the bacterium Azorhizobium caulinodans was transformed to express a SI-uptake system (Haskett et al. 2022). This system allowed a tight rhizopine-dependent control of factors driving the expression and activity of the nitrogenase from bacteria colonising the barley roots.
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[W]e demonstrated a novel experimental approach in which DNA from hexaploid wheat plants was modified to increase the production of a biofilm-stimulating metabolite. The apigenin exuded by the roots into the soil stimulated the formation of biofilms by the diazotrophic bacteria which protected the nitrogenase and induced biological nitrogen fixation. When grown at limiting N conditions, the modified wheat plants displayed increased growth and grain yield as compared to the control plants.
