Characterization of a fertilization-induced and developmentally regulated plasma-membrane aquaporin expressed in reproductive tissues, in the wild potato Solanum chacoense Bitt.

Fertilization triggers a unique and complex developmental program leading to embryogenesis and seed set. Growth and differentiation are accompanied by rapid metabolic changes as well as massive cellular reorganization inside the fertilized ovule. Using differential display to isolate genes involved in pollen-pistil interactions and early fertilization events, we isolated from Solanum chacoense Bitt. a fertilization-induced plasma-membrane intrinsic protein of the PIP2 family that is predominantly expressed in pistil and anthers tissues. Major intrinsic proteins (MIPs) consist of a large family of highly conserved membrane-spanning proteins that are mainly represented in plants by the aquaporins. Aquaporins, mainly of the PIP and TIP type, have been shown in many species to serve as water channels. In S. chacoense the ScPIP2a mRNA is developmentally regulated during anthesis, with mRNA levels gradually decreasing as the pistil reaches maturity. In flowers, strongest expression was observed in elongating styles, in stamens, and transiently in ovules following fertilization. In styles, maximal expression levels correlated with phases of rapid style elongation and with the formation of epidermal papillae. ScPIP2a mRNA was also strongly expressed in developing fruit, consistent with a role in cell expansion during maturation and development.