Functional characterization of a grape PIP2 gene.

Aquaporins facilitate transcellular transport of water, uncharged solutes, and CO2. The aim of this study was to assess the expression pattern of a PIP2 aquaporin of grape in different tissues. An aquaporin-like cDNA sequence was isolated based on a TIGR TC (TC38138) by RT-PCR. The complete sequence was cloned (VvPIP2, NCBI DQ358107) and expressed in Xenopus oocytes to prove water transport facilitation. A DNA probe was obtained and used for assessing expression in different organs using Northern hybridisation. An RNA probe was obtained and used to assess expression at the tissue level using in situ hybridisation. Functional experiments showed that VvPIP2 transports water, and is inhibited by Hg. VvPIP2 is mainly expressed in roots and little expressed in other vegetative organs In situ hybridisation confirms higher expression in the roots, low expression in leaves and no expression in shoots. In roots VvPIP2 expression is concentrated in the cortex of the subapical zone and in the xylem-surrounding cells of the absorbing roots. These results points to a role of this PIP2 in controlling radial water transport of water in the roots of grapevine.