MAP Kinase Cascades in Arabidopsis Innate Immunity

Abstract

Plant mitogen-activated protein kinase (MAPK) cascades generally transduce extracellular stimuli into cellular responses. These stimuli include the perception of pathogen-associated molecular patterns (PAMPs) by host transmembrane pattern recognition receptors which trigger MAPK-dependent innate immune responses. In the model Arabidopsis, molecular genetic evidence implicates a number of MAPK cascade components in PAMP signaling, and in responses to immunity-related phytohormones such as ethylene, jasmonate, and salicylate. In a few cases, cascade components have been directly linked to the transcription of target genes or to the regulation of phytohormone synthesis. Thus MAPKs are obvious targets for bacterial effector proteins and are likely guardees of resistance proteins, which mediate defense signaling in response to the action of effectors, or effector-triggered immunity. This mini-review discusses recent progress in this field with a focus on the Arabidopsis MAPKs MPK3, MPK4, MPK6, and MPK11 in their apparent pathways.

The Arabidopsis NUCLEUS- AND PHRAGMOPLAST-LOCALIZED KINASE1-Related Protein Kinases Are Required for Elicitor-Induced Oxidative Burst and Immunity

“…Response to hydrogen peroxide and to both OGs and elf18, as well as to flg22, involves the activation of MPK3 and MPK6 (Zipfel et al, 2006;Galletti et al, 2011;Rasmussen et al, 2012). MPK3 has been shown to be required for basal resistance to B. cinerea and does not significantly affect elicitor-induced resistance , whereas MPK6 is required for elicitor-induced resistance to B. cinerea and full expression of a subset of defense response genes but not for basal resistance to B. cinerea (Galletti et al, 2011).…”

“…MPK3 and MPK6 are activated also in response to both OGs (Galletti et al, 2011) and elf18 (Zipfel et al, 2006;Rasmussen et al, 2012), and MPK6 has been shown to be required for OG-and flg22-induced resistance to B. cinerea (Galletti et al, 2011). We investigated whether a compromised phosphorylation of MPK3/MPK6 in the anp mutants determines the defect in elicitor-induced defense responses.…”

“…Three immunerelated MAPK modules have been identified. A module comprising the MAP3K MEKK1, the MAP2Ks MKK1 and MKK2, and the MAPK MPK4 (MEKK1/MKK1-MKK2/ MPK4) negatively controls defense responses (Kong et al, 2012;Rasmussen et al, 2012) by negatively regulating the expression of the MAP3K MEKK2, which triggers a salicylate (SA)-dependent autoimmunity response when the cascade is compromised (Berriri et al, 2012;Su et al, 2013). Two other modules, MEKK1-MAPKKKa/MKK4-MKK5/MPK3-MPK6 and MKK9/ MPK3-MPK6 (Xu et al, 2008), mediate the activation of defense responses, including the synthesis of ethylene and camalexin, i.e.…”

The Heat Shock Factor A4A Confers Salt Tolerance and Is Regulated by Oxidative Stress and the Mitogen-Activated Protein Kinases MPK3 and MPK6

“…It is therefore intriguing that MPK3 and MPK6 were identified as central regulators of plant innate immunity, hypoxia, and salt and osmotic stress responses, which control cross talk between different stresses, hormonal signals, and second messengers, such a ROS (Droillard et al, 2002;Teige et al, 2004;Chang et al, 2012;Rasmussen et al, 2012;Smekalova et al, 2013). MAP kinases were reported to phosphorylate other transcription factors such as WRKY33, which is involved in regulation of ethylene biosynthesis (Li et al, 2012), or MYB44, which regulates abscisic acid sensitivity (Nguyen et al, 2012b).…”

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“…Mitogen-activated protein kinase (MAP kinase) cascades are critically involved in regulating plant defense mechanisms including plant innate immune responses [1]. Studies on the MAP kinase cascade in plants had led to the discovery of groups of genes interacting with each other to activate or inhibit defense related genes such as in pathogenesis related (PR) genes [2].…”