Supplement Supplement 1. Phylogenetic Relationship of SERK family in Arabidopsis and rice Arabidopsis thaliana: AtSERK1 (At1g71830), AtSERK2 (At1g34210), AtSERK3/AtBAK1 (At4g33430), AtSERK4 (At2g13790), AtSERK5 (At2g13800), At2g23950. Oryza (Os04g0457800), sativa: OsBAK1/OsSERK1 OsSERK3 (Os06g0225300), (Os08g0174700), OsSERK4 OsSERK2 (Os02g0283800), Os03g0703200, Os08g0442700. Tree was generated by PHYML (ML) and MEGA (NJ). Bootstrap values (ML/NJ) were shown. Supplement 2 Alignment of amino acid sequence of SERK family in Arabidopsis and rice. Proteins from the SERK family contain conserved construct, including a signal peptide, leucine zipper, five leucine-rich repeats (LRR1~LRR5), a Ser-Pro-Pro (SPP) motif, a hydrophobic transmembrane domain and a kinase domain. Amino acid residues conserved among all SERKs listed are shaded. The conserved activation loop located in the kinase domain is boxed. A Thr residue in the activation loop is essential for BAK1 function and is marked by ★. Percentages indicate amino acid similarity to AtBAK1 and OsSERK1. WG represents whole gene; KD represents kinase domain. Supplement 3. The expression of OsBRI1 and OsBZR1 in the OsBAK1 transgenic rice detected by real-time PCR. WT, Wild-type Zhonghua 10; d61-1, the weak rice BR-insensitive mutant; OE 1 (OsBAK1-OE), transgenic plants overexpressing OsBAK1; AS (OsBAK1-AS), transgenic plants suppressing OsBAK1 by antisense RNA; ICDΔ (OsBAK1-ICDΔ), transgenic plants overexpressing the truncated intracellular domain of OsBAK1; ECD (OsBAK1-ECD), transgenic plants overexpressing the extracellular domain of OsBAK1. 2 Supplement 1 3 Supplement 2 4 Supplement 3 5 Supplement 4 gene Use OsBAK1 OsBAK1-ICDΔ Gene isolation Rice transformation Arabidopsis transformation Gene isolation Arabidopsis transformation Gene isolation Arabidopsis transformation Gene isolation Arabidopsis transformation Rice transformation OsBAK1-AS Rice transformation OsBAK1-ECD Rice transformation BIFC GFP fusion OsSERK2 OsSERK3 OsSERK4 OsBAK1 Forward primer (restriction enzyme site underlined) 5'TCCCCCGGGAGGGTGGTGCTGATTTGG TGT3' (SmaI) Reverse primer (restriction enzyme site underlined) 5'GGGGTACCGTTCCTTGGGCTCCTGCTG TT 3' (KpnI) 5'GCTCTAGATTGGGTCCACTTGGCAGCG GTGAG3' (XbaI) 5'GGGGTACCAGGGCGAGGAAGCCGTCG AGCAAA3' (KpnI) 5'GGGGTACCCCCCACTCTGTTTACTCCC3 ' (KpnI) 5'CGAGCTCGGAATGGCAAGTGTTCTGTC T3' (SacI) 5'GGGGTACCTTCTTCTCCTCCTCCTCTT 3' 5'CGAGCTCGCAGAGTCATGGCTCTTTAG (KpnI) T3' (SacI) 5'GAAGATCTTCAGGGTGGTGCTGATTTG 5'GGGGTACCCCTCCTTGGGCTCCTGCTG GTGT 3' (BglII) used to amplified, BamHI TT 3' (KpnI) inside this gene used to ligase vector The same primers to that of OsBAK1-ICDΔ, KpnI (in primer) and SacI (inside this gene) was used to ligase the vector in antisense orientation 5'CGCGGATCCATGGCGGCGCATCGGTGG 5'CGGGGTACCATACCATGCAAAACCAAT GCGGTG3' (BamHI) AGCAGG 3' (KpnI) 5'CGGGGTACCAGAGGGTGGTGCTGATTT 5'CCGCTCGAGCCTCGGCCCTGATAGCTC GGTG 3' (KpnI) AAC 3' ( XhoI) 6 OsBRI1 OsBAK1 OsBAK1-ICD OsBAK1-ICDΔ AtPP2A AtCPD OsSERK2 OsSERK3 OsSERK4 OsBAK1-A OsBAK1-B OsBRI1 OsBZR1 OsD2 OsACTIN BIFC 5'GCTCTAGAATGGTCGTGAGGCAGTGAG C 3'' (XbaI) BIFC 5'GGACTAGTAATGCGTGATGTGTGAGAT C 3' (SpeI) BIFC 5'TGCTCTAGAATGTTCAGCAATAAAAAC ATTCT3' (XbaI) BIFC 5'TGCTCTAGAATGTTCAGCAATAAAAAC ATTCT3' (XbaI) used to amplified, BamHI inside this gene used to ligase vector Real-time PCR 5’GCTGTTGAGGGTTGTGCTG 3' Real-time PCR 5'TTACCGCAAAGCCATCCAA 3' Real-time PCR 5’CGGAGGGTGATGCCCTAT3' Real-time PCR 5’AAATCTTGAAGTGCTGGACTTG3' Real-time PCR 5’TGTCCTGTCCTTGGCTGGT3' Real-time PCR 5'GAGTTGATCTTGGGAATGCTGC 3' Real-time PCR specific 5' TCTTTGATGTGCCTGCTGA 3' for endogenous OsBAK1 level in OsBAK1-ECD Real-time PCR 5' AGCCTCAACTACATCAATGGGTC 3' Real-time PCR 5' ACCTACCGCAAGGGATGT 3' Real-time PCR 5' TCGGTGGTGTTCGAAATCCT 3' Real-time PCR 5'CGTATGAGCAAGGAGATCAC3' 7 5'CGGACTAGTATCCTTCTCCTCCTTGGCT T 3' (SpeI) 5'CGGGGTACCCCTCGGCCCTGATAGCTC AA 3 (KpnI) 5'CGGGGTACCCCTCGGCCCTGATAGCTC AA 3' (KpnI) 5'CGGGGTACCCCTCGGCCCTGATAGCTC AA 3' (KpnI) 5’GGCTGGCAGTAACGATTGTG 3' 5’TCATCACCACCACCGTCAAC 3' 5’CACGCTGTTGTCAGGGTTAC3' 5’GGTTATTGGAGAAACTGATTGG3' 5’GGCCAAGAGAAGCTGGTATTTC3' 5'CACTAGGTATCGTTCCGCTTATGTT3' 5' TTTATTGCTGAAGGTATCTGTTG 3' 5' GGTATCTCGCCCTCCAGCT 3' 5' CTCAGCAGCTGCGTTGAC 3' 5' ATGAGGCCGACAATAAATTCCT 3' 5'CACATCTGTTGGAAGGTGCT3'