Expression of Sorghum bicolor ammonium transporters upon colonization with arbuscular mycorrhizal fungi

SPE IPM CT1National audienceArbuscular mycorrhizal fungi (AMF) are important plant symbionts, trading mineral nutrients beyond the reach of roots, in particular ammonium, in exchange to their host’s photosynthetic products. Sorghum bicolor is one of the world's leading cereal crops, providing food, fibre and fuel across a range of environments and production systems. It has a particular ability to be productive even under strongly adverse conditions, tolerating much more severe drought than most other grain crops. As its genome has recently been sequenced, we have characterized all eight members of the ammonium transporter (AMT) family and studied their expression in different tissues of field-grown plants. While most of them were well expressed in all the tissues, SbAMT3;1 was predominantly and SbAMT4 was exclusively expressed in roots. Both were highly up-regulated (up to 70 and 20 times, respectively) in the presence of AMF. A split-root and a laser microdissection experiment have shown that SbAMT3;1 and SbAMT4 were locally but not systemically induced around arbuscules. Immunolocalization has indicated that the protein SbAMT3;1 was colocalized with mature arbuscules indicating a possible important role of this transporter in the AMF symbiosis