METABOLOMIC RESPONSE OF ISOLATED MAIZE EMBRYONIC AXES TO OXIDATIVE CONDITIONS SUBJECTED BY CADMIUM, METHYLVIOLOGEN AND HYDROGEN PEROXIDE

PENA L.B.; MORATTO CJ; ARÁN MARTÍN; MÉNDEZ AAE; MATAYOSHI C.L.; SUSANA M. GALLEGO

Congreso; LV ANNUAL SAIB- XIV PABMB 2019; 2019

The germination process starts with the uptake of water (imbibition) by the dry seed, followed by metabolism reactivation, and ends when radicleprotrudes. Successful seed germination will depend on the abilities of the embryo to gain its metabolic activity and for its capacity to cope withadverse environmental conditions. Although high levels of reactive oxygen species (ROS) produce oxidative stress, a basal level of ROS playsfundamental roles in the early stage of embryonic axes imbibitions. The objective of this study was to contribute to understanding the metabolomicadjustment that needs to be established for a successful equilibrium between growth and resistance. Intact embryo axes isolated from Zea mays cv.Chalqueño seeds were imbibed with 50 mM Tris-HCl pH 7.6, 50 mM KCl, 2% (w/v) sucrose, 10 mM MgCl2 without (C) or containing 10 μMCdCl2, 0.5 μM methylviologen (MV) or 1 mM H2O2. The study was focused on 24 and 48 h of imbibition. The absolute elongation rate of 0.43mm d-1 for control axes was reduced 60, 62, and 49 % in Cd-, MV- and H2O2-treated ones, respectively. Also, treatments disrupted cell redoxbalance by inducing the accumulation of O2- and H2O2 and modifying antioxidant enzymes defense system (catalase, superoxide dismutase,ascorbate and guaiacol peroxidases, glutathione and dehydroascorbate reductases). Oxidative cell damage was determined by the increase inprotein carbonylation. Increment in proteolytic activities was determined during the axes imbibitions and also during the oxidative conditionsgenerated by treatments. Water-methanol extracts were used to evaluate the polar metabolites profile using nuclear magnetic resonance (H1-NMR)spectroscopy. Hierarchical cluster analysis showed that after 24 h of imbibition, the metabolome of Cd-treated axes showed lower response respectto MV and H2O2 since its cluster was closer to the control. After 48 h of imbibitions, stress conditions clustered in a group that was distinct to thecontrol. Our results are indicating that during growth arrest, metabolic reorganization of the maize embryonic axes depends on an intense proteindegradation to produce free amino acids. This metabolic module would be necessary to improve the cell defense systems, by allowing the synthesisof new proteins and by maintaining metabolic homeostasis.