Light-dependent induction of OsPR10 in rice (Oryza sativa L.) seedlings by the global stress signaling molecule jasmonic acid and protein phosphatase 2A inhibitors

The OsPR10 gene was first shown to be weakly induced only 3 days after treatment with a herbicide, probenazole (N. Midoh, M. Iwata, Cloning and characterization of a probenazole-inducible gene for an intracellular pathogenesis-related protein in rice, Plant Cell Physiol. 37 (1996) 9-18), and remains uncharacterized till date. We provide first evidence for the induction of OsPR10 by the global signaling molecule, jasmonic acid (JA), and two protein phosphatase (PP) 2A inhibitors, cantharidin (CN) and endothall (EN). These inductions were light- and time-dependent, and also specific to the dose of applied JA, CN and EN. OsPR10 was not responsive to cut, and was expressed mainly in leaves and leaf sheaths, but not in roots. Furthermore, OsPR10 induction was blocked completely by cycloheximide, indicating requirement of de novo protein synthesis in its induction. Two signal transducers, salicylic acid (SA) and abscisic acid (ABA) induced OsPR10, and a cytokinin, kinetin (KN) also strongly up-regulated its expression, under light. Simultaneously applied staurosporine, a serine/threonine protein kinase inhibitor, strongly enhanced the JA inducible OsPR10 expression. The inducible nature of OsPR10 was affected significantly by a combination of applied JA, with varying concentrations of SA, ABA and KN. Induction of OsPR10 was followed by the appearance of necrotic lesions/coalescing necrotic regions clearly visible at 48 h under light, with CN and EN, but not with JA at a similar time period. Finally, using two-dimensional polyacrylamide gel electrophoresis, we identified a new member of the OsPR10 protein family, the OsPR10-3 protein. This represents the first systematic report in rice demonstrating that the inducible OsPR10 expression is light dependent, and may be regulated via a kinase-signaling cascade. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.