Identified a transporter that delivers iron to symbiotic nitrogen-fixing bacteria in root nodules

The massive use of nitrogen fertilizers in agriculture is responsible of feeding half of the world population. However, they are an important source of greenhouse gasses, one of the main expenses for farmers (unreacheable in many developing countries), and contribute to water eutrophyzation. Symbiotic nitrogen fixation (SNF) carried out by the rhizobia-legume interaction is one of the main alternatives to the overuse of these fertilizers, in a return to more sustainable practices of crop rotation with legumes. This process requires of relatively large amount of transition metals (iron, copper, zinc,…) that work as cofactors of many of the main enzymes participating in SNF. Given the prevalent low bioavailability of these metals in many of the main agricultural areas of the world, the real impact of crop rotation with legumes in soil nitrogen fertilization will depend in ensuring a continous and suficient delivery of essential transition metals. To improve this, we need to identify and manipulate the molecules mediating the delivery of these nutrients.

The CBGP group “Metal homeostasis in plant-microbe interactions”, in collaboration with researchers from Spain (ICA-CSIC), USA (Noble Reseach Institute and WPI), and France (CNRS and ESRF), has shown how ferroportin MtFPN2 participates in symbiotic nitrogen fixation. Embedded in the symbiosome membrane, MtFPN2 delivers the iron provided by the plant host to the colonizing nitrogen-fixing bacteria. Mutations in this transporter result in defective nodule development, altered iron distribution, and a loss of nitrogen fixation capabilities.