Engineer Perception of Nitrogen Fixing Bacteria

Nitrogen-fixing rhizobial bacteria are free-living in the soil and the first step in the legume/rhizobial symbiosis is a communication between the legume root cells and the bacteria. This is initiated by the release of signals from the plant, that in turn activate production of Nod factor by the bacteria. Recognition of Nod factor by the legume root is sufficient to activate many of the processes associated with the nitrogen-fixing symbiosis.

A legume root hair injected with calcium responsive dye to the calcium response indicating the perception of nitrogen fixing bacteria as a suitable symbiotic partner.

A detailed genetic dissection of nodulation in legumes has led to the discovery of the proteins involved in the signal transduction pathway that allows recognition of Nod factor and transmission of this signal to the activation of gene expression changes associated with accommodating the nitrogen-fixing bacteria.

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This signal transduction pathway has a second function in legumes: to allow the establishment of the beneficial arbuscular mycorrhizal symbiosis. This fungal symbiosis is widespread in the plant kingdom, including in cereals and the core of this signal transduction pathway is therefore present and functional in cereals.

In the ENSA project we are exploring how we can engineer this pre-existing signalling pathway in cereals to allow recognition of the nitrogen-fixing bacteria, in the manner with which it occurs in legumes.