Functional characterization of FaNIP1;1 gene， a ripening-related and receptacle-specific aquaporin in strawberry fruit.

Strawberry fruit (Fragaria × ananassa) is a soft fruit with high water content at ripe stage (more than 90% of its fresh weight). Aquaporins play an important role in plant water homeostasis， through the facilitation of water transport and solutes. We report the role played by FaNIP1;1 in the receptacle ripening process. The analysis by qRT-PCR of FaNIP1;1 showed that this gene is mainly expressed in fruit receptacle and has a ripening-related expression pattern that was accompanied by an increase in both the abscisic acid and water content of the receptacle throughout fruit ripening. Moreover， FaNIP1;1 was induced in situations of water deficit. Additionally， we show that FaNIP1;1 expression was positively regulated by abscisic acid and negatively regulated by auxins. The water transport capacity of FaNIP1;1 was determined by a stopped-flow spectroscopy in yeast over-expressing FaNIP1;1. Glycerol， H2O2 and boron transport were also demonstrated in yeast. On the other hand， GFP-FaNIP1;1 fusion protein was located in plasma membrane. In conclusion， FaNIP1;1 seems to play an important role increasing the plasma membrane permeability， that allows the water accumulation in the strawberry fruit receptacle throughout the ripening process.