Short CommuniCAtion Short CommuniCAtion

We are interested in the arbuscular mycorrhizal (AM) sym-biosis1,2 using Glomus mossea-inoculated sorghum (Sorghum bicolor) as a model system. Recently, we described the expanded family of ammonium transporters (AMTs) in sorghum.3 We could demonstrate that two AMTs, SbAMT3;1 and SbAMT4, are upregulated in mycorrhized plants (AM-inducible AMTs) and that SbAMT3;1 is localized at the plant-fungus interface. However, the biological significance of ammonium transport during symbiotic interaction remained elusive. Nitrate and ammonium represent the main sources of bio-available inorganic N in soils. Albeit their high mobility in soils, fixed N-depletion (in the vicinity of the root system) is a common environmental constraint plants have to cope with.2 Different studies estimated that AM fungi delivered between 30 % and 42 % of the N taken up by the plant.4,5 Mitigation o