Elucidating the systemic response of wheat plants under waterlogging based on transcriptomic and metabolic approaches.

Extreme weather conditions lead to significant imbalances in crop productivity, which in turn affect food security. Flooding events cause serious problems to many crop species such as wheat. Although metabolic readjustments under flooding are important for plant regeneration, underlying processes remain poorly understood. Here, we investigated the systemic response of wheat to waterlogging using metabolomics and transcriptomics. A 12-days exposure to excess water triggered nutritional imbalances and disruption of metabolite synthesis and translocation, reflected by reduction of plant biomass and growth performance. Metabolic and transcriptomic profiling in roots, xylem sap and leaves indicated anaerobic fermentation processes as a local response of the roots. Differentially expressed genes and ontological categories revealed that carbohydrate metabolism plays an important role in the systemic response. Analysis of the composition of xylem exudates exhibited decreased root-to-shoot translocation of nutrients, hormones and amino acids. Interestingly, among all metabolites determined in the xylem exudates, alanine was the most abundant. Alanine supplementation to excised leaves lead to increased glucose concentration when leaves derived from waterlogged plants. Our results suggest an important role of alanine not only as an amino-nitrogen donor but also as a vehicle for carbon skeletons to produce glucose de novo and meet the energy demand during waterlogging.