Study of vacuole volume changes kinetics: experimental and mathematical modelling approach

MOIRA SUTKA; VICTORIA VITALI; KARINA ALLEVA; GABRIELA AMODEO; OSVALDO CHARA

San Javier, Tucumán

Congreso; XLI Reunion anual de la Sociedad Argentina de biofisica; 2012

Plant vacuoles are responsible for cellular homeostasis, having in their membrane (the tonoplast) a transport system network that supports this role [1]. Clue members of this transport network are the aquaporins, protein channels that mediate water movements across tonoplast, membrane known to be involved in cytosolic volume regulation. We previously shown that under hypotonic conditions, initial rate of the vacuole volume change and final plateau value are both inhibited by acidification and mercury chloride in a dose- response manner [2]. In this work, a mathematical model, based on the Kedem-Katchalsky formalism [3] was developed to study the kinetic of vacuole volume. In order to characterize the model, exploration of the parameter space of water permeability-solute permeability (Pf-Ps) was performed. Furthermore, uncertain parameter analysis allowed the quantification of the model behaviour. Results indicate that Pf is the most influential parameter on the model response. The model allowed us to calculate water and solute permeability of tonoplast in the presence of different H+ (reflecting cytosolic pH) and HgCl2 concentration (reflecting aquaporin blockage), and explains how the vacuole volume at the plateau is reduced under acidification or by increasing the HgCl2 concentration. Our model predicts that mercury chloride and acidification would modulate both solute and water permeability determining the evolution of vacuole volume and total solute content. These results suggest that HgCl2 and pH triggers a cooperative manner to control vacuole volume by acting as aquaporin inhibitors as well as activating ion channels and/or transporters.