The modification of the DNA of two associated organisms, barley and a bacterium, aims to reduce the use of inputs. But the path is still long from the laboratory in the field.
by
This is one of the Grails of Agronomy: allow the main cereals – wheat, corn, barley or rice – which constitute half of the caloric intake of humanity, to capture the nitrogen of the Air as do legumes, limiting the spread of nitrogen fertilizers (nitrates), expensive energy and harmful to the environment and climate. A step in this path was crossed by researchers from the universities of Oxford, Cambridge and Norwich, as well as the MIT, which present Their results in the PNAs of April 11
Philip Pool (Oxford) and his colleagues had the idea of combining two genetically modified organisms, barley and a bacterium, to create a virtuous symbiosis. The barome of barley has been manipulated to produce a molecule, rhizopin, which serves as a signal to engage a cascade of reactions in the Azorhizobium Caulinodans bacterium, present in the roots of the plant, to make it capture. Nitrogen air. The bacterium had, for its part, been previously modified to respond conditionally to rhizopine.
One of the objectives pursued was that this association is beneficial only in the plant of interest, in this case barley, and that atmospheric nitrogen (n 2 ) Captured, transformed into ammonia (NH 3 ) by the bacterium, does not serve to fertilize “weeds”. That’s what was observed. But it remains the way to go before this proof of concept does not come to change the cultural practices. The researchers note, for example, that the nitrogenase activity, ensured by an enzyme that contributes to the production of ammonia, is still “suboptimal” in the genetically modified microorganism compared to the so-called “wild” bacteria.
“Very cunning” approach
Philip Pool believes that this work is “a key element of a vast effort to transfer root nodulation (specific to legumes) and the fixing of nitrogen to cereals. This was only possible thanks to A great collaboration effort bringing together the work done by multiple laboratories for many years. “
The Microbial Ecologist Yves Dessaux, former research director at the CNRS, whose work is cited in the PNA article, will not say the opposite. “These are ideas on which we already worked twenty-five years ago,” he says. He could not pursue them “lack of financing”, and in a context where GMOs were not in vogue. He welcomes the “very cunning” approach of his Congresses Anglo-Saxon. But notes that several obstacles will still have to be franchis.
“It will be necessary to verify that this really brings a plus to the plant under conditions where the intake of nitrogen by the soil is limiting,” he notes, for example. Indeed, cereals have other supply circuits of this fertilizer, which may be less “expensive” energy for them, and for bacteria that participate in this capture. It will also be necessary to see if Azorhizobium Caulinodans, put “against his will” in the service of barley, will not fit this function to restore his natural metabolism less energivorous for her. In addition, this new genetically modified symbiosis will most likely assume regular bacterial inoculants in the soil, the underground microcosm being ruthless with newcomers. As for regulatory obstacles, it can also be pledged that they will not fail.