A direct interaction of the Arabidopsis thaliana immunophilin ROF1 with 
phosphatidylinositol-3-phosphate and phosphatidylinositol-3,5-bisphosphate was 
identified using a phosphatidylinositol-phosphate affinity chromatography of 
cell suspension extracts, combined with a mass spectrometry (nano LC ESI-MS/MS) 
analysis. The first FK506 binding domain was shown sufficient to bind to both 
phosphatidylinositol-phosphate stereoisomers. GFP-tagged ROF1 under the control 
of a 35S promoter was localised in the cytoplasm and the cell periphery of 
Nicotiana tabacum leaf explants. Immunofluorescence microscopy of Arabidopsis 
thaliana root tips verified its cytoplasmic localization and membrane 
association and showed ROF1 localization in the elongation zone which was 
expanded to the meristematic zone in plants grown on high salt media. Endogenous 
ROF1 was shown to accumulate in response to high salt treatment in Arabidopsis 
thaliana young leaves as well as in seedlings germinated on high salt media 
(0.15 and 0.2 M NaCl) at both an mRNA and protein level. Plants over-expressing 
ROF1, (WSROF1OE), exhibited enhanced germination under salinity stress which was 
significantly reduced in the rof1(-) knock out mutants and abolished in the 
double mutants of ROF1 and of its interacting homologue ROF2 (WSrof1(-)/2(-)). 
Our results show that ROF1 plays an important role in the osmotic/salt stress 
responses of germinating Arabidopsis thaliana seedlings and suggest its 
involvement in salinity stress responses through a 
phosphatidylinositol-phosphate related protein quality control pathway.