General Responsibilities

From 1996 I am working at the University of Colima as a Professor of Physiology, since 1998 also accredited by SNI as a Federal Research Fellow. I am internationally recognized for the pioneering studies of the intracellular channels in plants. My current project, supported by the Mexican Research Council (CONACyT) is devoted to the role of polyamines in the control of plasma membrane ion transport under salt stress.

Polyamines are unique polycationic metabolites, which are known to control multiple cation channels in animal cells, some plant intracellular channels, and more recently, also several ones of the plant cell membranes. The latter, however, turned to be a much more complicated issue compared, as we found out that polyamine effects on plasma membrane ion channels in plants were indirect, thus, not easily reproducible on isolated membranes. This forced us to look up what happened in intact living tissues, by applying non-invasive MIFE technique and microelectrode impalements.

During my 4-months stay in Sergey´s lab supported by the Tasmanian University Visiting Fellowship, we were able to demonstrate that, in a species- and concentration-dependent manner, polyamines were able to provoke pronounced changes in the resting membrane potential (MP). Such changes will inevitably affect all electrogenic events and transports occurred at plasma membrane. It was very curious to see, that depending on its concentration within a physiological range, a natural tetra-amine spermine could evoke either negative or positive MP changes. Even more curiously, at higher achievable range of concentrations spermine provoked a sustained membrane depolarization. In contrast, the same plant, pea, which is considered to be salt-sensitive, although displaying a similar by magnitude initial depolarization while challenged by high external salinity, was able to restore the initial level of the MP within few minutes! Increase of polyamine levels is a common component of stress (e.g. salt) responses in plants, but obviously polyamines exert differential effects on ion transport as compared to the salt itself, which may be due to the activation of additional cation channels and/or suppression of the ion pumps activity. Both alternatives are intriguing, because classical view is that polyamines are normally the channel blockers and positive regulators of the pumps. We have shown also by a combination of MIFE and patch-clamp techniques that polyamines are able to potentiate the ionotropic effects of other stress molecules, in particular reactive oxygen species. This synergism implies that plant stress responses need to be investigated by a systemic approach, assuming the simultaneous and interactive effects of different key factors, rather than exploring the effects of a single isolated factor- an important lecture to be learned!