Asparagine accumulation in chicory storage roots is controlled by translocation and feedback regulation of asparagine biosynthesis in leaves

The presence of acrylamide (AA), a potentially carcinogenic and neurotoxic compound, in food has become a major concern for public health. AA in plant-derived food mainly arises from the reaction of the amino acid asparagine (Asn) and reducing sugars during the processing of foodstuffs at high temperatures. Using a selection of genotypes from the chicory germplasm we performed Asn measurements in storage roots and leaves to identify genotypes contrasting for Asn accumulation. We combined molecular analysis and grafting experiments to show that leaf to root translocation controls asparagine biosynthesis and accumulation in chicory storage roots. We could demonstrate that Asn accumulation in storage roots depends on Asn biosynthesis and transport from the leaf and that a negative feedback loop by Asn on CiASN1 expression impacts Asn biosynthesis in leaves. Our results provide a new model for asparagine biosynthesis in root crop species and highlight the importance of characterizing and manipulating asparagine transport to reduce AA content in processed plant-based foodstuffs.