P L A SMA MEMB R A N E A Q U A P O R I N S A R E DIFFERENTLY EXPRESSED IN HIGH AND LOW FIRMNESS STRAWBERRY CULTIVARS

MARQUEZ M; ALLEVA K; VILLARREAL NM; BUSTAMANTE CA; BELLATI J; MARTÍNEZ GA; CIVELLO PM; AMODEO G

Tucumán

Congreso; XLV Reunión Anual SAIB; 2009

SAIB

Fruit ripening studies are starting to consider aquaporinparticipation in fruit water status and its relevance in fruitphysiology. In previous work, we reported the cloning of twostrawberry fruit aquaporins showing differential behavior in termsof water permeability (Pf): high (FaPIP2,1) and low (FaPIP1;1). Tounderstand its participation in ripening, we investigate their patternexpression from large green to 100% red stages of two cultivars withcontrasting fruit firmness. Camarosa cultivar (firm fruit) showedhigh accumulation of FaPIP1;1 and FaPIP2;1 mRNAs. On theother hand, in the softer cultivar (Toyonoka), aquaporins expressionwas less marked.To further characterize their functional properties, we confirm thatthe co/expression of these subtypes in Xenopus oocytes enhanceswater permeability, generating a response that surpasses the sum oftheir individual contribution. Moreover, this high waterpermeability is modulated by cytosolic pH, showing 98% reductionin its final value when pH is reduced to 6.0. In the same conditions, intFaPIP2;1 expressed alone shows only partial inhibition (78%).In conclusion, strawberry cultivars of different firmness presentdifferent expression levels of FaPIP2;1, an aquaporin that not onlyshows high water permeability properties but also modulatesmembrane Pf when coexpressed with FaPIP1;1.