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Mechanism of Phosphate Sensing and Signaling Revealed by Rice SPX1-PHR2 Complex StructureMechanism of Phosphate Sensing and Signaling Revealed by Rice SPX1-PHR2 Complex Structure
Structural highlights
FunctionPHR2_ORYSJ Transcription factor involved in phosphate starvation signaling (PubMed:18263782, PubMed:26082401). Binds to P1BS, an imperfect palindromic sequence 5'-GNATATNC-3', to promote the expression of inorganic phosphate (Pi) starvation-responsive genes (PubMed:25657119, PubMed:26082401). Functionally redundant with PHR1 and PHR3 in regulating Pi starvation response and Pi homeostasis (PubMed:26082401). Involved in both systematic and local Pi-signaling pathways (PubMed:19704822). Regulates several Pi transporters (PubMed:18263782). Regulates the expression of PT2 (PubMed:20149131). Directly up-regulates SPX1 and SPX2 expression, but PHR2 binding to DNA is repressed redundantly by SPX1 and SPX2 in a PI-dependent manner (PubMed:25271318). The DNA-binding activity is also repressed by SPX4 (PubMed:24692424). Involved in root growth under Pi deprivation (PubMed:18263782). Involved in the modulation of Pi response and homeostasis together with RLI1; promotes RLI1 expression in response to nitrate availability, thus triggering the nitrate-induced phosphate response (NIPR) (PubMed:33316467, PubMed:35640569).[1] [2] [3] [4] [5] [6] [7] [8] [9] Publication Abstract from PubMedPhosphate, a key plant nutrient, is perceived through inositol polyphosphates (InsPs) by SPX domain-containing proteins. SPX1 an inhibit the PHR2 transcription factor to maintain Pi homeostasis. How SPX1 recognizes an InsP molecule and represses transcription activation by PHR2 remains unclear. Here we show that, upon binding InsP(6), SPX1 can disrupt PHR2 dimers and form a 1:1 SPX1-PHR2 complex. The complex structure reveals that SPX1 helix alpha1 can impose a steric hindrance when interacting with the PHR2 dimer. By stabilizing helix alpha1, InsP(6) allosterically decouples the PHR2 dimer and stabilizes the SPX1-PHR2 interaction. In doing so, InsP(6) further allows SPX1 to engage with the PHR2 MYB domain and sterically block its interaction with DNA. Taken together, our results suggest that, upon sensing the surrogate signals of phosphate, SPX1 inhibits PHR2 via a dual mechanism that attenuates dimerization and DNA binding activities of PHR2. Mechanism of phosphate sensing and signaling revealed by rice SPX1-PHR2 complex structure.,Zhou J, Hu Q, Xiao X, Yao D, Ge S, Ye J, Li H, Cai R, Liu R, Meng F, Wang C, Zhu JK, Lei M, Xing W Nat Commun. 2021 Dec 2;12(1):7040. doi: 10.1038/s41467-021-27391-5. PMID:34857773[10] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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