Expression Analysis of Oryza sativa Ascorbate Peroxidase 1 (OsAPx1) in Response to Different Phytohormones and Pathogens Wang, Yiming; Wu, Jingni; Choi, Young Whan; Jun, Tae Hwan; Kwon, Soon Wook; Choi, In Soo; Kim, Yong Chul; Gupta, Ravi; Kim, Sun Tae;
We have isolated and characterized an ascorbate peroxidase (APx) gene, OsAPx1 from rice. Northern and Western blot analyses indicated that at young seedling stage, OsAPx1 mRNA was expressed highly in root, shoot apical meristem (SAM) and leaf sheath than leaf. In mature plant, OsAPx1 gene expressed highly in root, stem and flower but weakly in leaf. OsAPx1 gene and protein expression level was induced in leaves inoculated with Magnaporthe oryzae (M. oryzae) and Xanthomonas oryzae pv. oryzae (Xoo). Phytohormones treatment showed that OsAPx1 was up-regulated by jasmonic acid (JA), but was down regulated by ABA and SA co-treatments with JA, resulting that they have antagonistic effect on pathogen responsive OsAPx1 expression. Phylogenetic analysis illustrated that Arabidopsis AtAPx1 has a close relationship with OsAPx1. In AtAPx1 knock out lines, the accumulation of O2- and H2O2 are all highly detected than wild type, revealing that the high concentration of exogenous H2O2 cause the intercellular superoxide anion and hydrogen peroxide accumulation in AtAPx1 knockout plant. These results suggested that OsAPx1 gene may be associated with the pathogen defense cascades as the mediator for balancing redox state by acting ROS scavenger and is associated with response to the pathogen defense via Jasmonic acid signaling pathway.