PAL activity assays were conducted according to the method of Qin and Tian [24]. Three grams of rice leaf was homogenized with 30 mL of 50 mmol L− 1 sodium borate buffer (pH 8.8, containing 5 mmol L− 1 β-mercaptoethanol) and 0.5 g of polyvinyl pyrrolidone (PVP) and ground using a polytron tissue grinder at 4 °C. The mixture was centrifuged at 15,000 × g for 30 min at 4 °C, and the supernatant was collected for enzyme analysis. One milliliter of enzyme extract was incubated with 2 mL of borate buffer (50 mmol L− 1, pH 8.8) and 0.5 mL of l-phenylalanine (20 mmol L− 1) for 60 min at 37 °C. The reaction
was stopped with 0.1 mL of 6 mol L− 1 HCl. PI3K inhibitor The PAL activity was determined by the production of cinnamate, measured by the absorbance change at 290 nm with a spectrophotometer (UV-160, Japan). PPO and POD were extracted according to the method of Chen et al. [20]. Rice samples (3 g) from each treatment were homogenized with 30 mL of 0.1 mol L− 1 sodium phosphate buffer (pH 6.4) containing 0.5 g of PVP and ground at 4 °C. The homogenate was centrifuged at 15,000 × g for 30 min at 4 °C, and the supernatant was used for
Selleckchem Bleomycin enzyme assays. The PPO activity was determined by adding 1 mL of enzyme preparation to 2 mL of catechol as a substrate, and the change was measured immediately in absorbance at 398 nm (A398). The activity was expressed as A398 per minute per milligram of protein. The POD activity was determined using guaiacol as a substrate. The
reaction mixture consisted of 2 mL of crude extract, 1 mL of guaiacol, and 1 mL of buffer. The reaction mixture was incubated at 30 °C for 30 min before 1 mL of H2O2 was added. Absorbance was measured at 460 nm (A460). The activity of POD was defined as A460 per minute per milligram of protein [24]. Statistical analysis was performed with SPSS10.0 software for multiple comparisons and correlation analyses. A value of P < 0.05 was considered to be statistically significant. 1% Agarose gel electrophoresis and UV spectrophotometry were used to detect the quality of the total RNA, and indicated that the extracted RNA was suitable for reverse transcription. The PCR amplified fragments 4-Aminobutyrate aminotransferase of the target gene PAL showed that the cDNA was specific without background bands or false positive amplification ( Fig. 1). PAL (phenylalanine ammonia-lyase), EDS1 (enhanced disease susceptibility 1) and PAD4 (phytoalexin deficient 4) are the major genes involved in the SA-synthesis pathway. The relative expression level of PAL was significantly higher in resistant Kasalath rice than in the susceptible Wuyujing 3 cultivar in response to SBPH feeding. The relative expression level of PAL in rice at 12 hpi was 7.52 times greater than that in untreated control rice at the same time point.