Figure 3.

BRs antagonize SA-mediated root immunity against P. graminicola. A, Exogenous BL (1 μm) attenuates BTH-induced resistance. For chemical induction of resistance, seeds were briefly dipped into a BTH solution (0.5 mm) and subsequently sown on GB5 medium containing 50 mg L²¹ BTH. BL treatment, pathogen inoculation, and disease evaluation was performed exactly as described in legend to Figure 1. Different letters indicate statistically significant differences (Mann-Whitney; n = 12; α = 0.05). Representative pictures were taken 7 dpi. Minus sign (−) = mock control, plus sign (+) = infected. B, Effect of BRZ pretreatment (1 μm) on Pythium susceptibility in wild-type Nipponbare and SA-deficient NahG plants. Statistically significant differences between treatments are labeled with different letters (Mann-Whitney; n = 24; α = 0.05). Numbers below graph represent disease index values. C, qRT-PCR analysis of the SA regulatory genes OsWRKY45 and OsNPR1 in control and BL-treated Nipponbare roots inoculated with P. graminicola. Transcript levels were normalized using actin as an internal reference and for each time point expressed relative to mock-inoculated controls. Data are means ± sd of two technical and two biological replicates from a representative experiment, each biological replicate representing a pooled sample from at least six individual plants. D, BRZ-induced resistance is compromised in OsWRKY45 and OsNPR1 RNAi lines. All genotypes were pretreated with 1 μm BRZ and subsequently inoculated with P. graminicola PB912 132. Bars labeled with different letters are significantly different (Mann-Whitney; n = 24; α = 0.05). All experiments were repeated at least twice with similar results. [See online article for color version of this figure.]