*4.3. Measurement of H2O2*

Rice suspension-cultured cells were prepared using a previously published method [5,39]. Modified liquid N6 medium (30 g L−<sup>1</sup> sucrose; 4.1 mg L−<sup>1</sup> N6 salt (Wako, Osaka, Japan); 2 mg L−<sup>1</sup> glycine; 0.5 mg L−<sup>1</sup> nicotinic acid; 0.5 mg L−<sup>1</sup> pyridoxine HCl; 1 mg L−<sup>1</sup> thiamine HCl; 100 mg L−<sup>1</sup> myo-inositol; 1 mg L−<sup>1</sup> 2,4-dichlorophenoxyacetic acid; 23.4 mg L−<sup>1</sup> MnSO4·4H2O; pH 5.8) was used for liquid cultivation. We treated 1 mL media containing 100 mg suspension-cultured cells with 10 μg mL−<sup>1</sup> peptidoglycan from *Bacillus subtilis* (Sigma-Aldrich, St. Louis, MO, USA), 50 μg mL−<sup>1</sup> LPS from *Pseudomonas aeruginosa* 10 purified by phenol extraction (Sigma-Aldrich), 10 nM *N*-acetylchitohexaose (chitin elicitor (CE)), or an autoclaved suspension of *X. oryzae* pv. *oryzae* (OD600 = 0.3).

To prepare leaf strips, the sixth leaves of GUS-HPB:OX and BSR1-HPB:OX17 plants at the 6–6.5-leaf stage were used. Two fragments of the leaf blades (8-mm length and 6-mm width) that were slit using bundled razor blades at approximately 0.5-mm intervals were placed in a well of a 12-well plate. Leaf strips were floated on sterile water and incubated at 28 ◦C for 14–15 h with shaking at 90 rpm, followed by a 1-h incubation in new water. Conidia of rice blast fungus were scraped from the gel surface with sterile water and filtered through a Kimwipe. The conidial concentration in the filtrate was calculated using a hemocytometer. A suspension of autoclaved or living conidia was poured into the wells to the indicated final concentration and incubated at 28 ◦C. The H2O2 concentration was determined at the indicated time using a previously described luminol-dependent chemiluminescence assay [5]. The statistical analyses were carried out using Dunnett's test for the experiments with cultured cells and Student's *t*-test for the experiments with leaf strips.

#### *4.4. Quantitative Reverse Transcription (qRT)-PCR*

Cultured rice cells were frozen in liquid nitrogen after a 3-h treatment with 10 μg mL−<sup>1</sup> peptidoglycan, 50 μg mL−<sup>1</sup> LPS, 10 nM *N*-acetylchitohexaose, an autoclaved suspension of *X. oryzae* pv. *oryzae* (OD600 = 0.3), or sterile water. Total RNA extraction and the qRT-PCR were performed as previously described [39]. Transcript levels were analyzed using the comparative CT (2−ΔΔCt) method with rice *Ubiquitin1* (*RUBQ1*; Os06g0681400) as an internal control [50,51]. The statistical analysis was carried out with Tukey's test. The primers presented in Supplementary Materials Table S1 were used for the qRT-PCR analyses.
