Molecule Characterization And Corresponding Biological Functions Of Phosphate Transporter Genes In Wheat (Triticum Aestivum L.)

As the mediaters in uptake and transportation of Pi in plants, phosphate transporters play important roles on regulation of acquisition and utilization of Pi under various Pi-supply conditions. Update, relative few studies on wheat phosphate transporter genes have been carried out compared with those reported in model plant Arabidopsis and rice, two plant species with whole genome sequences released currently. In this study, eleven putative wheat phosphate transpoter (PT) genes have been identified based on bioinformatic analysis. The wheat PT genes have been subjected to further analysis such as identification of molecular features, detection of expression patterns under various Pi-supply conditions. The main results are as follows.1. Based on search in the international GenBank for the putative wheat PT genes, in total 11 genes sharing the PT features have been identified. They were designated as TaPT1, TaPT2, TaPT3, TaPT4, TaPT5, TaPT6, TaPT7, TaPT8, TaPT9, TaPT10 and TaPT11, respectively.2. The open reading frames of TaPT1 to TaPT11 varied from 660 bp (TaPT11) to 1707 bp (TaPT3), encoding the poplypeptides changing from 219-aa to 568-aa. Transmembrane prediction analysis suggested that the transmembrane domans between 3-5. Furthermore, phylogenetic analysis displayed that all the tested wheat PT genes are possibly derived from different ancestors.3. Using Shixin828, a wheat cultivar to be high P-use efficiency, to be the material, the expression patterns of the 11 wheat PT genes (TaPT1~TaPT11) under low-Pi stress condition were detected. It is found that TaPT1, TaPT4, TaPT8 and TaPT10 were constitutively expressed, no responding to the external Pi variation. The expression of TaPT2, TaPT3, TaPT5, TaPT6, TaPT7, TaPT9 and TaPT11 were regulated by the low-Pi signaling. Among them, TaPT2, TaPT3, TaPT6 and TaPT7 were shown to be up-regulated, whereas TaPT5, TaPT9 and TaPT11 were behaved to be down-regulated. These wheat PT genes are possibly involved in responding to low-Pi stress via various molecular pathways.4. Using Chinese Spring as the material, the diurnal rhythm of gene expression patterns of 11 tested wheat PT genes were analyzed. Under normal Pi-supply condition, TaPT3 and TaPT5 were shown to be constitutive, as well as TaPT11 in roots and leaves under low-Pi stress condition. In addition, TaPT2 and TaPT6 in roots, TaPT9 in leaves under nomal Pi-supply condition, and TaPT2, TaPT5 and TaPT6 in roots and TaPT9, TaPT3 and TaPT7 in leaves under low-Pi stress condition were all aslo constitutively expressed. Under low-Pi stress condition, the expression of TaPT1 in roots during the day-time was higher than that during the dark-time, whereas the expression of TaPT4 in roots during the day-time was lower than that during the dark-time. The expression levels of TaPT5 in roots, TaPT3 and TaPT7 in leaves under normal Pi-supply condition, and TaPT5 in roots and leaves, TaPT3 and TaPT7 in leaves under low-Pi stress condition were all displayed higher than others. These results have implicated that TaPT3, TaPT5 and TaPT7 possibly play much more important roles than other wheat PT genes.5. Based on DNA recombinant technology and gene genetic transformation approach, the transgenic tobacco plant lines with overexpression of TaPT1, TaPT3 and TaPT4 were generated. In contrast to the control plants, the transgenic plants displayed much higher Pi acquisition abilities under low-Pi stress conditon, with much more plant accumulative phosphorus amount, fresh and dry weight per leaves than the control plants. Furthermore, the transgenic plants had higher contents of photosynthetic pigments and soluble protein than the control plants under low-Pi stress condition. Taken together, the increase of Pi uptaked in the transgenic plants is the critical factor to improve the plant physiological parameters and the plant gorwth phenotypes under low-Pi stress condition via alleviation of the cellular Pi stress degree.6. The genetic transformation system with high efficiency in wheat has been established. The transgenic wheat plants fused the sense open reading frame sequences of TaPT1 and TaPT4 were generated, which have paved the basis for further understanding of the wheat PT gene functions in future.