title: The paralogous SPX3 and SPX5 genes redundantly modulate Pi homeostasis in rice.
abstract: The importance of SPX-domain-containing proteins to phosphate (Pi) homeostasis and signalling transduction has been established in plants. In this study, phylogenetic analysis revealed that OsSPX3 and OsSPX5 (SPX3/5) are paralogous SPX genes ( SYG1/Pho81/XPR1) in cereal crops. SPX3/5 are specifically responsive to Pi starvation at both the transcriptional and post-transcriptional levels. Similar tissue expression patterns of the two genes and proteins were identified by in situ hybridization and the transgenic plants harbouring SPX3pro-SPX3-GUS or SPX5pro-SPX5-GUS fusions, respectively. Both SPX3/5 are localized in the nucleus and cytoplasm in rice protoplasts and plants. SPX3/5 negatively regulate root-to-shoot Pi translocation with redundant function. The data showed that the Pi-starvation-accumulated SPX3/5 proteins are players in restoring phosphate balance following phosphate starvation. In vitro and in vivo protein-protein interaction analyses indicated that these two proteins can form homodimers and heterodimers, also implying their functional redundancy. Genetic interaction analysis indicated that SPX3/5 are functional repressors of OsPHR2 (PHR2), the rice orthologue of the central regulator AtPHR1 for Pi homeostasis and Pi signalling. These results suggest that the evolution of the additional redundant paralogous SPX genes is beneficial to plants recovering Pi homeostasis after Pi starvation by PHR2 pathway.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Shi
authors.forename: Han
authors.initials: H
authors.lastname: Hu
authors.forename: Keming
authors.initials: K
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Yanan
authors.initials: Y
authors.lastname: Yu
authors.forename: Zhongchang
authors.initials: Z
authors.lastname: Wu
authors.forename: Ping
authors.initials: P
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D019281:Dimerization; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D006706:Homeostasis; D008969:Molecular Sequence Data; D009928:Organ Specificity; D012275:Oryza / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D010710:Phosphates / Q000172:deficiency / Q000378:metabolism*; D010802:Phylogeny; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000502:physiology; D018520:Plant Shoots / Q000166:cytology / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
chemical_list: D010710:Phosphates; D010940:Plant Proteins
keywords: Negative regulation; Oryza sativa L.; Pi homeostasis; SPX proteins.; protein interaction