1. Figure S1 Figure S1. Modular structure of rice proteins encompassing the SPX domain. Different colors indicate the amino acid ranges of the domains. Purple, SPX domain; blue, EXS domain; yellow, MFS domain; red, RING- type Zinc finger domain; pink, no conserved domain.

2. Figure S2 Figure S2. Expression analysis of OsSPX-MFS1, OsSPX-MFS2 and OsSPX-MFS3 in leaves and roots.

3. Figure S3 Figure S3. Expression analysis of OsSPX-MFS1, OsSPX-MFS2, OsSPX-MFS3 and osa-miR827 under different Pi starvation treatments. Seeds were geminated and growth on nutrient solution with different Pi concentration for three weeks. Roots were sampled separately for analysis. All data are means of three biological replicates with error bars indicating SD. Expression of OsACTIN was used as the internal control. nd indicates non-detectable.

4. Figure S4 acctctctagttcattttgtgagagagctctacccagctccgctcccatattagatagaactgaaactgtttggttga gcttcagctccaggagagatggagctagagctggagccgtgccaaacaggaccatctaggtactgacacgtgta G-box gaaaatacttcccggagctttggttcttctgttccactccacccatcggcacaggcgggcgtctgcactctgggcctc tggcgtgcggcgcccgcgcgtggtctggttgcgcagcgcgctgcgccgggtggaatccgttgcggcggcgtacac cgtcacggcgtcacacactcacaccagcgccgcgcgccgcgggggacgtcagggactcgcgcgggccatgcag gttgggctggctctcggcctctcgcctgtatctcaagggggtagcagcccattgcgtcggtagacctaggactcccc ccgtgggccggtcacgtggagtcgtacgtggccctcgtcgatagcgccgcaggcctctctcaccacaagtccacg G-box atgctgccccgaggatggttgtacacatggtagaacagtccgagaggggaacaattttgcctacaaattatccaca E-box actttgcgagcgtttcatccgttccgaacagtccccttcctctgctgccccatcatcgctcatatctggattttttttttg aaaggagtatatctggatatatataataccccttcgtactcgtaaagaaaattgtttaggacaatgtttaagtcaga ccttgaaaatataaatcataaataactctcaaattgttgagtttgaaaatataaaaattatataaatagatttgtctt TATA box TATA box gaaaaatattttcataaaagtatacatataatactttcaataaatatttttttatagaaacaataagtaaaagttgtat tttagagaccgtgtcactgtccaaaatgactttctctacgagtaagagagagtattcctttttttttcatgactggaca W-box W-box accgcaaaatccacgcgttcgtccgctggtacaactcctccctgtcacggctaatttaccaagaccgttgatccaaa tctacgctcatcatctccacctagcagaagaggcagtacagtcagccagtggcacagcgtcagcgtcactacaga gtgtgcacgtacatacatgttgctgactgtctcctgcttaattacttgatgcttccatgtcgtcgtgcttctgcggggg W-box acggtttattcctcgcgaatatgcctctaattcgctggcatcaacgtaccatcatcccttccgtgcacgcacctaccc P1BS gatccaaaatatatccttcgcttcaatacagcactagcagcttcatctcattcgccccatcttccagtcttccaggcgt ccagctccagtttcttctcattgacaatatatccagattatgctctgggcttgctaattgctactagtagaatactagg ggtggtcgtggtgtgcaggtgagattattgctacCCATGAACCTGTTTTGTTGCTGGTCAT CTAGCTACCCGTGCATGCCTGGAGATTGGAGAATAATTGACGATGCA GCAGTCGGCTTATTGGCTCTTGGGCACGCGTGGTTAGATGACCATCA GCAAACAAGTTCGTGAG Figure S4. Nucleotide sequence of the promoter and gene region of osa-miR827. The letters in capital indicates the precursor sequence of osa-miR827. The cis- elements of the promoter region were colored in red.

5. Figure S5 Figure S5. Expression analysis ofOsSPX-MFS1 (A), OsSPX-MFS2 (B), OsSPX-MFS3 (C) and Pri-miR827 (D) in osa-miR827 overexpression lines and msf1in the roots. Seeds were geminated and growth on nutrient solution with high Pi concentration (HP, 10 mg/L) and low Pi concentration (LP, 0.1 mg/L) for three weeks. Total RNA was extracted from the roots and used for qRT-PCR. All data are means of three biological replicates with error bars indicating SD. Expression of OsACTIN was used as the internal control. WT, wild type; Oe1/2/3, osa- miR827 overexpression lines; mfs1, OsSPX-MFS1 mutant line NC2634.

6. Primer Name Forward （ 5` → 3` ） Reverse （ 5` → 3` ） OsSPX-MFS1GCGATTCTTGGGTGTACTGTCGTGAAAGCAACGACAGGTT OsSPX-MFS2CCTCCTGAATGTAACCCTGAGGAACTGTGTCAACTGCTT OsSPX-MFS3CGATTGGTTCAGCATACAGAGTGCTGAGACGACATACTGG Pre-miR827TCTAGCTACCCGTGCATGCCGCGTGCCCAAGAGCCAATAA OsSPX1GACCAGCTTCTACCATCAAACGAGTTCCTGCTGCTCCTCTGG OsIPS1AAGGGCAGGGCACACTCCACATTATCATTAGAGCAAGGACCGAAACACAAAC OsPAP10ATACTGGCAGCCGACGGATGAGAGGGAGCTGGAGCGGAGAA OsACP1AGATGGAGGAGACGCTGCTGTCGCAATCCTCACACACACAT OsPT2CACAAACTTCCTCGGTATGCTGAAACCCCACAAATCCACAAC OsPT3AGACGGTGGTTCAACAGAGGCAAACCAAACTAACAAAATACC OsPT7CTTGCTCGGCTTCCTCCTGCCATTATTTCATCATCCAGC OsPT8CCTACTTGTGTTTGTCTATGTGGTGCCAAATTGCTGGTCTG Tos17-3'ATTGTTAGGTTGCAAGTTAGTTAAGA NC2634GTTTTGCGGTTCTGCTTCTCTCCACCAAATCCTGACCAAC OsSPX-MFS1:ProACTCCACAAGGATTGGCTCCGCTTGTCGTTCAATACCTGTATC miR827-OeGATCGGATCCGGGTGGTCGTGGTGTGCAGGTGATCGGATCCCAAATGAACCAGAGAATCGAC Table S1. Sequences of the primer sets used in the study

7. Gene nameGene locusProtein lengthcDNA accession No.Total EST OsSPX-MFS1Loc_Os04g48390696AK0660689 OsSPX-MFS2Loc_Os02g45520697AK24135918 OsSPX-MFS3Loc_Os06g03860698AK243620182 OsSPX-MFS4Loc_Os09g34990570NF Table S2. Information of OsSPX-MFS genes in rice