Cloning and characterization of a jasmonate inducible rice ( Oryza sativa L.) peroxidase gene, OsPOX, against global signaling molecules and certain inhibitors of kinase-signaling cascade(s)

Abstract

We report the characterization of a rice peroxidase ( OsPOX) gene, identified from screening a jasmonic acid (JA)-treated rice seedling leaf cDNA library, whose nucleotide sequence was essentially similar to the previously cloned pathogen inducible OSPER/POX22.3. However, it remains totally uncharacterized against global signaling molecules mediating defense/stress response(s), with little information on its regulation. OsPOX showed a weak constitutive expression in rice seedling leaf, and was highly responsive to cut. The cut inducible OsPOX transcript was further enhanced by the global signaling molecules jasmonic acid (JA), salicylic acid (SA), and ethylene (using the ethylene generator ethephon, ET). Strong induction of OsPOX expression by protein phosphatase 2A inhibitors, cantharidin (CN) and endothall (EN), and use of staurosporine alone or with JA, CN and EN suggested a role for the kinase-signaling cascades in its regulation. These inductions were light/dark-, and time-dependent, and required a certain de novo synthesized protein factor(s). Surprisingly, among other phytohormonal components of the signaling cascades, abscisic acid (ABA) down regulated the induced OsPOX expression, whereas a cytokinin, kinetin (KN) strongly induced its expression. As the JA induced OsPOX expression was almost abolished by SA and ABA, but slightly enhanced with KN, an interaction among these signaling molecules in modulating OsPOX expression is suggested. Present study clearly demonstrates that signaling molecules known to act as or generate cellular signals mediating the plant's response to stress/pathogen infection modulate the OsPOX expression.