Characterization of rice polyphenol oxidase promoter in transgenic Arabidopsis thaliana

Abstract

Polyphenol oxidase (PPO) enzymes are ubiquitous in plant kingdom and catalyze the oxidation of phenols to highly reactive quinones. The PPO gene plays an important role in plant defense mechanisms against biotic and abiotic stresses but the regulation of PPO promoter in stresses remains unclear. Here Oryza sativa (OsPPO) promoter was fused to firefly Luciferase (LUC) and β-glucuronidase (GUS) reporter genes separately to test the effects of wounding, abscisic acid (ABA), and methyl jasmonate (MeJ) applications on PPO promoter induction. To the best of our knowledge, this is the first report about rice PPO promoter induction in response to wounding and ABA characterized by RT-PCR. Transcriptional profiling of reporter genes by real-time (RT) PCR in transgenic Arabidopsis revealed ~2.5-fold induction under PPO promoter directed activity in response to ABA treatment. Moreover, a strong induction of 11-fold was observed in response to wounding in reporter gene transcripts under control of OsPPO promoter. Plant cis-acting regulatory DNA elements signal scanning of OsPPO promoter also showed homologies to ABA cis-regulatory element signaling complexes and wound responsive elements (W-boxes) residing within the 1020 bp promoter region. Wound and ABA inducibility of OsPPO promoter is a strong indicator of its role in the plant defense mechanism against abiotic and biotic stresses.