Root Exuded Benzoxazinoids: Uptake and Translocation in Neighbouring Plants

Plants have evolved advanced chemical defence mechanisms, including root exudation, which enables them to respond to changes occurring in their surroundings rapidly. Yet, it remains unresolved how root exudation effects belowground plant-plant interactions. The objective of this study was to elucidate the fate of benzoxazinoids (BXs) exuded from roots of rye (Secale cereale L.) plants grown with hairy vetch (Vicia villosa). A rapid method that allows non-destructive and reproducible chemical profiling of the root exudates was developed. Targeted chemical analysis with HPLC-MS/MS was performed to investigate the changes in the composition and concentration of BXs in the rye plant and its root exudate in response to co-cultivation with hairy vetch. Furthermore, hairy vetch plants were screened for possible uptake of BXs from the rhizosphere and their translocation to the shoot. Rye significantly increased the production and root exudation of BXs, in particular 2-β-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one (DIBOA-glc) and 2-β-D-glucopyranosyloxy-4-hydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA-glc), in response to co-cultivation with hairy vetch. DIBOA-glc and DIMBOA-glc were absorbed by the roots of the co-cultivated hairy vetch plants and translocated to the shoots. These findings will strongly improve our understanding about the exudation of BXs from rye plant and their role in interaction with other plant species. Keywords: Benzoxazinoids; DIBOA-glc; DIMBOA-glc; Root exudate; Plant-plant interactions.