PLANT AQUAPORIN CO-EXPRESSION SENSES DIFFERENTIALLY THE INTRACELLUAR pH

KARINA ALLEVA, JORGE BELLATI, MERCEDES MARQUEZ, VICTORIA VITALI, CINTIA JOZEFKOWICZ, GABRIELA SOTO, GABRIELA AMODEO

Boston, Estados Unidos

Congreso; Congreso Internacional ASPB; 2010

American Society of plant Biologist

The plant plasma membrane (PM) expresses two types of aquaporins: PIP1 and PIP2. These PIP are characterized by: i- the faculty to reduce water permeation through the pore after cytosolic acidification as a consequence of gating process, ii- the ability to modulate membrane water permeability by co-expression of both types. We investigated if these functional characteristics of PIP can act together to give a new and relevant modulation response to acidification. To test our hypothesis we used PIP1 and PIP2 from different plant sources (Beta vulgaris roots and Fragaria x ananassa fruits). The experimental approach used was to perform a functional study of PIP by means of the heterologous expression system Xenopus oocytes and analyzed the oocyte PM water permeability coefficient (Pf) when PIP are injected. Briefly, the Pf was increased ten-fold by PIP2, but it remained low for both control oocytes and PIP1 injected ones. Moreover, when oocytes expressed PIP2, a partial (70%) pH inhibitory response under cytosolic acidification (pH 6) was detected. When PIP1-PIP2 co-expression was assayed, Pf was enhanced seven-fold in comparison with Pf obtained by PIP2 expression alone. Furthermore, the pH dependent behavior showed that PIP1-PIP2 co-expression accounts for different pH sensitivity by shifting the EC50 of the inhibitory response from pH 6.1 to pH 6.9, compared to PIP2. Our results show that: i- PIP co-expression impacts on the membrane water permeability not only by modulating the water transport capacity but also the pH regulatory response, improving in this way membrane plasticity, ii- this PIP behavior is not a tissue specific and/or species-dependent response but a more general one.