Abstract
The mitogen-activated protein kinases (MAPKs) are key molecules of signal transduction responses to various extracellular stimuli. In tobacco, two pathogen- and wound-induced MAPKs, WIPK and SIPK, regulate stress-induced accumulation of jasmonic and salicylic acids. MAPK phosphatases (MKPs) are negative regulators of MAPKs. We have reported that overexpression of NtMKP1, a tobacco calmodulin-binding MKP, compromised wound-induced activation of WIPK and SIPK. In this study, we investigated the changes in the levels of NtMKP1 transcripts and proteins in response to wounding. Quantitative RT-PCR analysis revealed that NtMKP1 mRNA is once decreased and then increased in response to wounding. The level of NtMKP1 protein was investigated by immunoblot analysis; however it was not detected in the wild type plants. Therefore, we used the plants expressing NtMKP1 under Cauliflower mosaic virus 35S promoter. The level of NtMKP1 protein was rapidly decreased, kept at the lower level for several hours and then returned to the basal level after wounding. These results indicated that NtMKP1 is regulated at both transcriptional and post-transcriptional levels.
