Monitoring spatial and temporal metabolic dynamics of woody poplar root under mechanical stress conditions by NMR-based metabolomics

Introduction Molecular factors are differentially observed in various bent sectors of poplar (Populus nigra) woody taproots. Responses to stress are modulated by a complex interplay among different hormones and signal transduction pathways. In recent years, metabolomics has been recognized as a powerful tool to characterize metabolic network regulation, and it has been widely applied to investigate plant responses to biotic and abiotic stresses. Objectives In this paper we used metabolomics to understand if long term-bending stress induces a spatial and a temporal metabolic reprogramming in woody poplar roots. Methods By NMR spectroscopy and statistical analysis we investigated the unstressed and three portions of stressed root (above-bent, bent, and below-bent) sectors collected at 12 (T-0), 13 (T-1) and 14 (T-2) months after stress induction. Results The data indicate a clear between-class separation of control and stressed regions, based on the metabolites regulation, during both spatial and temporal changes. We found that taproots, as a consequence of the stress, try to restore homeostasis and normal metabolic fluxes thorough the synthesis and/or accumulation of specific compounds related to mechanical forces distribution along the bent taproot. Conclusion The data demonstrate that the impact of mechanical stress on plant biology can efficiently be studied by NMR-based metabolomics.