OsPTF1: A Novel Phosphorus-starvation Induced Transcription Factor Involved In Tolerance For Phosphorus Starvation In Rice (Oryza Sativa L.)

A transcription factor with bHLH domain was isolated from a phosphorus (P) starvation induced rice (Kasalath) cDNA library constructed by Suppression subtracted hybridization (SSH), and designated as OsPTFl. The results from the cloning and chacteriazation of the gene, and transgenic plants experiments are summarized as follows:1 Full-length cDNA of OsPTFl was cloned using 3' and 5' RACE. Southern blotting analysis indicates that it is a single copy gene in rice genome and consists of eight exons. It was mapped on chromosome 6 at a QTL for phosphorus-deficiency tolerance flanked by C498 and R1954 using the genetic population derived from a cross between Kasalath as high P ?efficient parent and Nippobbare as low P-efficient parent. The 416 Pro was substituted with Thr in the low P-efficient parent Nippobbare.2 A OsPTFl: GFP fusion protein was localized in the nucleus. In vitro, OsPTFl protein can bind to G-box element (a type of E-box element). A auto-activation domain was found in the N-terminal region of OsPTFl protein based on yeast two hybridization system.3 RT-PCR and Northern blotting analysis indicate that OsPTFl is phosphate (Pi)starvation induced in roots while constitutive in shoots. Report gene and in situ hybridization indicate the expression of OsPTFl in leaf, lateral root and root phloem except for epidermic cells in root.4 Solution culture experiments showed that biomass yield and Pi content of transgenic plants with over expression of OsPTFl were about 30% higher than those of wild type rice under low phosphate level (0.5 mg P/L), and about 20-30% lower in transgenic plants with RNAi of OsPTFl than those in wild type rice. Under high Pi level (10 mg P/L), biomass yield and P content in transgenic plants of RNAi of OsPTFl were decreased by 30% and 20%, respectively. Instantaneous Pi uptake rate of transgenic plants with over expression of OsPTFl was increased. The results strongly suggested that OsPTFl is Pi-starvation induced transcription factor involved in the Pi-starvation tolerance in rice.