OXIDATIVE STRESS IN PLANT LIPID MEMBRANES: An electro-biophysical approach.

CORVALÁN, NATALIA ANDREA; FELSZTYNA, IVÁN; ENET, ALEJANDRO; CAVIGLIA, AGUSTÍN; LASCANO, HERNÁN RAMIRO

Santos

Congreso; XLII Congress of the Brazilian Biophysics Society; 2017

Brazilian Biophysics Society

Environmental stress conditions, such as strong light, drought, salinity, heat, and cold, which all promote an exacerbated reactive oxygen species (ROS) production, represent risk factors to cellular redox homeostasis. Depending on the severity of stress, namely, the intensity and duration of stress conditions, a delicate balance between cell death and signaling will take place. This implies a dual role of ROS, as toxic or as signaling molecules, since they are able to modulate defense responses, acclimation, growth and development, and cell death by oxidative reactions. ROS are different activation states of O2, as singlet oxygen (1O2), or reduction states, as superoxide radical (O2-), hydrogen peroxide (H2O2) and hydroxyl radical (?OH), being this latter highly toxic to cellular metabolism because its high reactivity to different macromolecules. Cell membrane systems, whose integrity is crucial to the plant physiology, are one of the main targets of oxidative processes mediated by ROS. These chemical species interact with unsaturated fatty acids of membrane lipids triggering a peroxidation chain reaction to produce lipid hydroperoxides in a process known as lipoperoxidation (LPO). But how crucial are the electro-biophysical membrane changes induced by LPO to the cell, how these changes modulate cellular response and ?susceptibility? to environmental physicochemical signals, or how membrane functionality is affected by membrane lipid order changes remain poorly understood. In the present work, a thorough analysis of the electro-biophysical properties of planar lipid bilayers (BLMs) composed of a complex mixture of purified lipids from Plasma Membrane of soybean leaves (Glycine max L) was performed under different stress conditions with the aim of improving our understanding of the basic underlying processes of oxidative membrane damage that occur when plants are subjected to unfavorable environmental conditions. Oxidative treatments with different types (hydrogen peroxide and hydroxyl radical) and ROS concentrations were applied. Our preliminary results show Membrane Capacitance (C) as a critical order and structural parameter which shows a nonlinear increment (biphasic behavior) in response to thresholds of ROS concentrations and exposure time to ROS. Moreover, abrupt changes (transitions) in membrane resistance and conductance occur associated to capacitance changes when BLMsoy are subjected to oxidative treatments. Taking into account C depends on membrane area (A), and the molecular area and fluctuations increase in oxidized lipids, the capacitive behavior would seem respond to structural and organizational changes induced by oxidative damage and would be able to modulate electrical membrane properties and, in consequence, signaling processes at cellular level.