FaPIP2;1 a novel aquaporin differently expressed in high and low firmness strawberry cultivars

MARQUEZ M., ALLEVA K., MUT P., VILLARREAL N., BUSTAMANTE C., BELLATI J., MARTÍNEZ G., CIVELLO M., AMODEO G.

Tucumán. Argentina

Congreso; XLV Reunión de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2009

SAIB

Fruit ripening studies are starting to consider aquaporin participation in fruit water status and its relevance in fruit physiology. In previous work, we reported the cloning of two strawberry fruit aquaporins showing differential behavior in terms of water permeability (Pf): high (FaPIP2;1) and low (FaPIP1;1). To understand its participation in ripening, we investigate their pattern expression from large green to 100% red stages of two cultivars with contrasting fruit firmness. Camarosa cultivar (firm fruit) showed high accumulation of FaPIP1;1 and FaPIP2;1 mRNAs. On the other hand, in the softer cultivar (Toyonoka), aquaporins expression was less marked. To further characterize their functional properties, we confirm that the coexpression of these subtypes in Xenopus oocytes enhances water permeability, generating a response that surpasses the sum of their individual contribution. Moreover, this high water permeability is modulated by cytosolic pH, showing 98% reduction in its final value when pHint is reduced to 6.0. In the same conditions, FaPIP2;1 expressed alone shows only partial inhibition (78%). In conclusion, strawberry cultivars of different firmness present different expression levels of FaPIP2;1, an aquaporin that not only shows high water permeability properties but also modulates membrane Pf when coexpressed with FaPIP1;1.