The mitogen-activated protein kinases WIPK and SIPK regulate the levels of jasmonic and salicylic acids in wounded tobacco plants.

In tobacco (Nicotiana tabacum), wounding causes rapid activation of two mitogen-activated protein kinases (MAPKs), wound-induced protein kinase (WIPK) and salicylic acid (SA)-induced protein kinase (SIPK), and the subsequent accumulation of jasmonic acid (JA). Our previous studies suggested that activation of WIPK is required for the production of wound-induced JA. However, the exact role of WIPK remains unresolved. We generated transgenic tobacco plants in which either WIPK or SIPK were silenced using RNA interference to define the roles of WIPK and SIPK in the wound response. In addition, transgenic tobacco plants were generated in which both WIPK and SIPK were silenced to examine the possibility that they have redundant roles. Wound-induced JA production was reduced compared with non-silenced plants in all of the WIPK-, SIPK- and WIPK/SIPK-silenced plants. Transgenic plants over-expressing NtMKP1, a gene encoding tobacco MAPK phosphatase, which inactivates WIPK and SIPK, also exhibited reduced JA production in response to wounding. In both WIPK/SIPK-silenced and NtMKP1-over-expressing plants, wounding resulted in an abnormal accumulation of both SA and transcripts for SA-responsive genes. These results suggest that WIPK and SIPK play an important role in JA production in response to wounding, and that they function cooperatively to control SA biosynthesis.