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The rice(Oryza sativa L.) genome contains at least six genes exclusively with an SPX(SYG1/PHO81/XPR1) domain at the N-terminal,designated as OsSPX1-6.Here we report the diverse expression patterns of the OsSPX genes in different tissues and their responses to Pi-starvation.Among them,five genes,OsSPX1,2,3,5 and 6 are responsive to Pi-starvation in shoots and/or in roots.The subcellular localization analysis indicates that OsSPX1 and OsSPX2 is exclusively located in nucleus,OsSPX3 in the cytoplasm,and OsSPX4 is a membrane localization protein.OsSPX1 regulates OsSPX2,3 and 5 at the transcription level and is positively involved in the responses of the genes to Pi-starvation.Overexpression of OsSPX3 downregulates OsSPX5 in shoots under Pi-sufficiency.OsSPX3 negatively regulates the PSI(Pi-starvation induced) gene,OsIPS1 and is involved in the responses of miR399 and OsPHO2 to Pi-starvation.Our results suggest that OsSPX1 may be a regulator involved in the transcriptions of OsSPX2,3 and 5.OsSPX3 plays a role in OsIPS1/miR399 mediated long distance regulation on OsPHO2.Our results also indicate that OsSPX3 is involved in plant tolerance to Pi-starvation stress.
The rice (Oryza sativa L.) genome contains at least six genes exclusively with an SPX (SYG1 / PHO81 / XPR1) domain at the N-terminal designated as OsSPX1-6. Here we report the diverse expression patterns of the OsSPX genes in different tissues and their responses to Pi-starvation. Among them, five genes, OsSPX1, 2, 3, 5 and 6 are responsive to Pi-starvation in shoots and / or in roots.The subcellular localization analysis that said OsSPX1 and OsSPX2 is exclusively located in nucleus, OsSPX3 in the cytoplasm, and OsSPX4 is a membrane localization protein. OsSPX1 regulates OsSPX2, 3 and 5 at the transcription level and is positively involved in the responses of the genes to Pi-starvation. Overexpression of OsSPX3 downregulates OsSPX5 in shoots under Pi-sufficiency. OsSPX3 negatively regulates the PSI (Pi-starvation induced) gene, OsIPS1 and is involved in the responses of miR399 and OsPHO2 to Pi-starvation. Our results suggest that OsSPX1 may be a regulator involved in the transcriptions of OsSPX2, 3 and 5. OsSPX3 plays a role in OsIPS1 / miR399 mediated long distance regulation on OsPHO2.Our results also indicate that OsSPX3 is involved in plant tolerance to Pi-starvation stress.