Study On Phosphate Transport Function Of G3Pps In Arabidopsis Thaliana

Phosphorus?P?,an essential macronutrient for plant growth and development,plays vital roles in most metabolic processes in plants.Inorganic or thophosphate(PO₄^3-or Pi)is the major form of P taken up by most organisms,however,its limited availability in the environment is often a restricting factor for the growth of plants.Pi transporters are located in cell membranes,which catalyze the transport of Pi.An earlier study of global gene expression revealed that the expression of Glycerol-3-phosphate permease?G3Pp?family?comprises five members,AtG3Pp1-5?was induced during Pi deficiency in Arabidopsis.In this study,we report the functional characterization of G3Pp1/2/3 to testify the assumption that G3Pp acts as a vacuolar Pi transporter and mobilizes Pi from intracellular stores.An alignment of amino acid sequences of G3Pps revealed the presence of conserved residues,contributing to the conserved SPX-MFS domain.Transmembrane and topology prediction indicated that there were 12 transmembrane domains in G3Pp1 protein with both amino and carboxyl terminals facing the cytosol,whereas both G3Pp2 and G3Pp3 contained 11transmembrane domains with carboxyl terminals facing the vacuolar lumen.Transiently expressing each of these G3Pp proteins fused to green fluorescent protein?GFP?in tobacco protoplasts verified that they were located on the vacuolar membrane using laser scan cofocal microscopy.The results of histochemical?-glucuronidase?GUS?staining of transgenic plants expression a pG3Pp genmome fragmen:GUS showed that G3Pp1 gene was expressed in roots,stems and leaves during all growth stages;and G3Pp2 and G3Pp3 were expressed primarily in the roots and cotyledons of the seedling stage.Pi deficiency?2.5?M?resulted in a pronounced GUS activity of both G3Pp1 and G3Pp3 in the root system.Consistent with this result,the transcription of G3Pp3 was upregulated significantly by real-time quantitative PCR analysis.The G3Pp1/2/3 mutant plants retained higher phosphate concentration and inhibited of primary root growth than the wild type.Therefore,G3Pp1/2/3 as a pi transporter involved in subcellular Pi allocation.Plasma membrane targeting CBL-CIPK pathways play an indispensable role for the plants's adaption to the changeable environment,by regulating the influx and efflux of inorganic nutrients ions,such as Na⁺,K⁺,Mg²⁺and H⁺in plant cells.Using yeast two-hybrid screening and bimolecular fluorescence complementation assay,G3Pp1,G3Pp2 and G3Pp3 were found to interact with CIPK11,21 and 26 on the tonoplast,respectively.