Tomato MAPKKKε is a positive regulator of cell-death signaling networks associated with plant immunity

Shiri Melech-Bonfil, Guido Sessa*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Mitogen-activated protein (MAP) kinase cascades are fundamental components of the signaling pathways associated with plant immunity. Despite the large number of MAP kinase kinase kinases (MAPKKK) encoded in the plant genome, only very few of them have an assigned function. Here, we identified MAPKKK gene of tomato (Solanum lycopersicum), SlMAPKKKε, which is required for hypersensitive response cell death and disease resistance against Gram-negative bacterial pathogens. Silencing of SlMAPKKKε compromised tomato resistance to Xanthomonas campestris and Pseudomonas syringae strains, resulting in the appearance of disease symptoms and enhanced bacterial growth. In addition, silencing of NbMAPKKKε in Nicotiana benthamiana plants significantly inhibited the cell death triggered by expression of different R gene/effector gene pairs. Conversely, overexpression of either the full-length SlMAPKKKε gene or its kinase domain in N.benthamiana leaves caused pathogen-independent activation of cell death that required an intact kinase catalytic domain. Moreover, by suppressing the expression of various MAPKK and MAPK genes and overexpressing the SlMAPKKKε kinase domain, we identified a signaling cascade acting downstream of SlMAPKKKε that includes MEK2, WIPK and SIPK. Additional epistasis experiments revealed that SIPKK functions as a negative regulator of SlMAPKKKε-mediated cell death. Our results provide evidence that SlMAPKKKε is a signaling molecule that positively regulates cell death networks associated with plant immunity.

Original languageEnglish
Pages (from-to)379-391
Number of pages13
JournalPlant Journal
Issue number3
StatePublished - Nov 2010


  • MAP kinase
  • Plant immunity
  • Pseudomonas syringae pv. tomato
  • Tomato
  • Virus-induced gene silencing
  • Xanthomonas campestris pv. vesicatoria


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