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<p>Abstract</p> <p>Background</p> <p>Mitogen activated protein kinase (MAPK) cascade is an important signaling cascade that operates in stress signal transduction in plants. The biologically active monoterpenoid indole alkaloids (MIA) produced in <it>Catharanthus roseus</it> are known to be induced under several abiotic stress conditions such as wounding, UV-B etc. However involvement of any signaling component in the accumulation of MIAs remains poorly investigated so far. Here we report isolation of a novel abiotic stress inducible <it>Catharanthus roseus</it> MAPK, <it>CrMPK3</it> that may have role in accumulation of MIAs in response to abiotic stress.</p> <p>Results</p> <p>CrMPK3 expressed in bacterial system is an active kinase as it showed auto-phosphorylation and phosphorylation of Myelin Basic Protein. CrMPK3 though localized in cytoplasm, moves to nucleus upon wounding. Wounding, UV treatment and MeJA application on <it>C. roseus</it> leaves resulted in the transcript accumulation of <it>CrMPK3</it> as well as activation of MAPK in <it>C. roseus</it> leaves. Immuno-precipitation followed by immunoblot analysis revealed that wounding, UV treatment and methyl jasmonate (MeJA) activate CrMPK3<it>.</it> Transient over-expression of <it>CrMPK3</it> in <it>C. roseus</it> leaf tissue showed enhanced expression of key MIA biosynthesis pathway genes and also accumulation of specific MIAs.</p> <p>Conclusion</p> <p>Results from our study suggest a possible involvement of <it>CrMPK3</it> in abiotic stress signal transduction towards regulation of transcripts of key MIA biosynthetic pathway genes, regulators and accumulation of major MIAs.</p>