Transient regulation of jasmonic acid-inducible rice MAP kinase gene (OsBWMK1) by diverse biotic and abiotic stresses

We report on japonica-type (cv. Nipponbare) rice seedling characterization of a jasmonic acid-inducible mitogen-activated protein kinase (MAPK) gene (identical to the previously isolated blast- and wound-inducible first functional MAPK gene, BWMK1 from indica-type rice, accession number AF177392), and hence termed OsBWMK1. As BWMK1 was shown to be induced in leaves by blast infection and wounding, only after around 4 h and 30 min, respectively, it remains completely unknown as to how this MAPK behaves in response to other external stimuli. We consistently detected that the weak constitutive mRNA expression of OsBWMK1 was potently enhanced and transiently regulated within 15 min of wounding (by cut) and treatment with diverse stressors, such as global signaling molecules, fungal elicitor, protein phosphatase inhibitors, heavy metals, high salt and sucrose, and drought. Interestingly, high temperature (37 °C), but not low temperature (12 °C), and notorious environmental pollutants—ozone and sulfur dioxide—also strongly induced the OsBWMK1 transcript within 15–30 min of treatment, suggesting that OsBWMK1 converges diverse stress signals in rice. Treatment with cycloheximide suggests the possible involvement of a certain de novo synthesized protein factor(s) in its transient regulation. These results strongly suggest the physiological importance of OsBWMK1 in mediating multiple extrinsic signals in rice.