A COMPARATIVE STUDY OF PLASMA MEMBRANE AND TONOPLAST AQUAPORINS SHOWS DIFFERENT REGULATORY MECHANISMS

MOIRA SUTKA; KARINA ALLEVA; MARIO PARISI; GABRIELA AMODEO

Iguazú, Misiones, Argentina

Congreso; XL Reunión Anual de la Sociedad Argentina Investigación Bioquímica y Biología Molecular.; 2004

Sociedad Argentina Investigación Bioquímica y Biología Molecular.

Water balance in plants is a topic under continuous study due to its physiological relevance. In previous works we demonstrated the presence of a transcellular water pathway sensible to mercurial compounds in Beta vulgaris storage roots and functional evidences of the existence of aquaporins in plasma membrane (PIPs) and tonoplast (TIPs) of these root cells. To further investigate the contribution of the water permeability of these two main membranes in water transport, we perform two approaches: molecular detection of aquaporins (western blot) and experiments to discriminate differential regulation of the two subfamilies of water channel (volume changes of vesicles under osmotic shock followed by light scattering). The obtained results showed: 1) high water permeability values in both membrane fractions; 2) the presence of PIP1 and PIP2 in PM fractions and TIP3:1 in TP fraction, 3) different inhibitory effects by HgCl2 and 4) a complete blockage by acidic pH of PIPs contrasting with only a partial blockage of TIPs. We postulate that this different behaviour of aquaporins in both membranes allow a fine tuning of water redistribution in the cell to cell pathway.