Effect of salicylic acid on expression of some defense-related genes in rice

Different investigations have shown that salicylic acid (SA) plays a key role in plant resistance induction against environmental stresses specially diseases. Pathogen attack induced systemic acquired resistance (SAR) in plants accompanied with increasing of endogenous SA, which activates wide signal transduction pathways such as transcription of the pathogenesis related proteins (PRP), enzymes related to phytoalexins biosynthesis and ABC transporter pump. Therefore, the effect of salicylic acid on the expression of defense-related genes including PDR8, PDR5, PDR4, PDR3, NPR1, Thionin, PDF1.2 and PR1 was investigated using Real Time PCR technique in two cultivars Khazar (as resistant to blast) and Hashemi (as susceptible to blast) in 0, 6, 12, 24 and 48 hours after SA treatment. Results showed that the expression of the all studied genes was increased by SA treatment. The expression of the PR1, PDF1.2 and PDR3 was increased in cultivar Khazar while no significant differences was observed among different times of SA treatment in Hashemi. Also the expression of PDR5 and PDR8 was increased significantly in cultivar Hashemi 48 h after SA treatment. Totally, it could be concluded that SA exogenous treatment of rice might increase the expression of the defense genes and probably induce plant resistance against pathogen attack. In addition, the expression pattern of the defense related genes largely depends on plant genetic background.