Expression and functional analysis of the rice plasma-membrane intrinsic protein gene family

Plasma membrane intrinsic proteins (PIPs) are a subfamily of aquaporins that enable fast and controlled translocationof water across the membrane.In this study,we systematically identified and cloned ten PIP genes from rice.Based on thesimilarity of the amino acid sequences they encoded,these rice PIP genes were classified into two groups and designatedas OsPIPI-1 to OsPIP1-3 and OsPIP2-1 to OsPIP2-7 following the nomenclature of PIP genes in maize.QuantitativeRT-PCR analysis identified three root-specific and one leaf-specific OsPIP genes.Furthermore,the expression profile ofeach OsPIP gene in response to salt,drought and ABA treatment was examined in detail.Analysis on transgenic plantsover-expressing of either OsPIP1 (OsPIPI-1) or OsPIP2 (OsPIP2-2) in wild-type Arabidopsis,showed enhanced toler-ance to salt (100 mM of NaCl) and drought (200 mM of mannitol),but not to salt treatment of higher concentration (150mM of NaCl).Taken together,these data suggest a distinct role of each OsPIP gene in response to different stresses,andshould add a new layer to the understanding of the physiological function of rice PIP genes.