A mitogen-activated protein kinase (MAPK) pathway has been demonstrated as a key pathway in plant defense against pathogen attacks. With proteomics approaches, we specifically studied activation events downstream of a MAPK kinase, tMEK2, in tomato. Overexpression of a constitutively activated tomato MAPK kinase gene (tMEK2MUT) enhanced resistance of transgenic tomato lines to the virulent bacterial pathogen Pseudomonas syringae pv. tomato. Pathogenesis-related genes, PR1b1, β-1,3-glucanase, and endochitinase were up-regulated by tMEK2MUT. Two-dimensional electrophoresis and matrix-assisted laser desorption/ionisation-time-of-flight-mass spectrometry analysis of total soluble leaf proteins indicated that β-1,3-glucanase and endochitinase are among the up-regulated proteins in these transgenic plants. Co-expression studies using a transient gene expression system have indicated that β-1,3-glucanase and endochitinase genes up-regulated by tMEK2 MUT were down-regulated by different specific phosphatases through dephosphorylation of certain downstream signaling molecules. Our observations indicate that increased products of β-1,3-glucanase and endochitinase genes downstream of tMEK2 may play an important role in achieving disease resistance. Crown Copyright

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Keywords Lycopersicon esculentum L., MALDI-TOF, MAPKK, Plant defense, Signal divergence, Tomato
Persistent URL dx.doi.org/10.1016/S0885-5765(03)00062-6
Journal Physiological and Molecular Plant Pathology
Xing, T, Rampitsch, C. (Chris), Miki, B.L. (Brian L.), Mauthe, W. (Wayne), Stebbing, J.-A. (Jo-Ann), Malik, K. (Kamal), & Jordan, M. (Mark). (2003). MALDI-Qq-TOF-MS and transient gene expression analysis indicated co-enhancement of β-1,3-glucanase and endochitinase by tMEK2 and the involvement of divergent pathways. Physiological and Molecular Plant Pathology, 62(4), 209–217. doi:10.1016/S0885-5765(03)00062-6