Jasmonate, salicylate, protein phosphatase 2A inhibitors and kinetin up-regulate OsPR5 expression in cut-responsive rice (Oryza sativa)

The rice OsPR5 gene, initially identified in response to pathogen attack, remains completely uncharacterized against global signaling molecules involved in defense/stress. Here, we provide evidence that OsPR5 expression, which is weakly constitutive in rice seedling leaves, is responsive to cut, and is up-regulated by jasmonic acid (JA), salicylic acid (SA), and protein phosphatase (PP) 2A inhibitors, cantharidin (CN) and endothall (EN), in a light/dark-, time-, and dose-dependent manner. Furthermore, except for the cut control, which showed considerable increase in the OsPR5 transcript with cycloheximide (CHX), a consistent partial suppression in the JA, SA, CN and EN induced OsPR5 transcript levels by CHX might suggest a requirement for de novo protein synthesis downstream of these chemical agents. Moreover, co-application of SA, ABA, and kinetin (which also up-regulated the OsPR5 transcript) with JA was found to further modulate the induced mRNA level of OsPR5. These results provide insight into the regulation of OsPR5 expression by signaling molecules and their co-application, and additionally implied a role for phosphorylation/dephosphorylation events in its regulation.