The effect of different nitrogen sources on the symbiotic interaction between Sorghum bicolor and Glomus intraradices: Expression of plant and fungal genes involved in nitrogen assimilation

• A major part of nitrogen is delivered to plants through a mycorrhizal pathway.
• Dry weight, N content and root colonization of the plant depends on the N source.
• Nitrogen metabolism differs between the extra- and intra-radical mycelium.
• Nitrogen source has an impact on plant and fungal gene expression.
• Gene expression patterns were similar between plant and fungal genes.

In the arbuscular mycorrhizal (AM) symbiosis, plants take up part of the nitrogen (N) through a mycorrhizal pathway. In this study, we assessed the effect of different N sources on the expression of genes coding for enzymes and transporters of the mycorrhizal N uptake pathway, using Sorghum bicolor and Glomus intraradices as a model. Some of the genes investigated were differentially regulated in the intraradical and in the extraradical mycelium depending on the N source. In AM roots, some fungal and plant genes were co-regulated, suggesting an interdependence of both partners in the mycorrhizal N uptake pathway. Mycorrhizal N transfer may have a preference for glycine (plant growth and N uptake stimulation).