Mitogen-Activated Protein Kinases 3 and 6 Are Required for Full Priming of Stress Responses inArabidopsis thaliana   

Abstract

In plants and animals, induced resistance (IR) to biotic and abiotic stress is associated with priming of cells for faster and stronger activation of defense responses. It has been hypothesized that cell priming involves accumulation of latent signaling components that are not used until challenge exposure to stress. However, the identity of such signaling components has remained elusive. Here, we show that during development of chemically induced resistance in Arabidopsis thaliana, priming is associated with accumulation of mRNA and inactive proteins of mitogen-activated protein kinases (MPKs), MPK3 and MPK6. Upon challenge exposure to biotic or abiotic stress, these two enzymes were more strongly activated in primed plants than in nonprimed plants. This elevated activation was linked to enhanced defense gene expression and development of IR. Strong elicitation of stress-induced MPK3 and MPK6 activity is also seen in the constitutive priming mutant edr1, while activity was attenuated in the priming-deficient npr1 mutant. Moreover, priming of defense gene expression and IR were lost or reduced in mpk3 or mpk6 mutants. Our findings argue that prestress deposition of the signaling components MPK3 and MPK6 is a critical step in priming plants for full induction of defense responses during IR.

Arabidopsis MPK3 and MPK6 Play Different Roles in Basal and Oligogalacturonide- or Flagellin-Induced Resistance against Botrytis cinerea

“…For instance, MPK3 is an important regulator of benzothiadiazole-induced priming of defense gene activation, while MPK6 appears to play a minor role in this response (Beckers et al, 2009). Furthermore, MPK6 has a stronger effect on the up-regulation of genes involved in camalexin biosynthesis that are induced by the expression of a constitutively active MAPKKK, while MPK3 plays a major role in camalexin accumulation and disease development during B. cinerea infection (Ren et al, 2008).…”

“…In contrast to MPK4, increasing evidence indicates that MPK3 and MPK6 exert a positive role on the activation of Arabidopsis defense responses. For instance, they have been shown to regulate camalexin accumulation (Ren et al, 2008) and ethylene (ET) production during fungal infection, and to be required for chemically induced priming of stress responses (Beckers et al, 2009).…”

Impact of root exudates and plant defense signaling on bacterial communities in the rhizosphere. A review

“…Instead, an accelerated activation of plant defenses occurs upon pathogen recognition, providing a stronger and faster defense response. Possible mechanisms of priming in SAR and ISR involve the expression of signaling components such as transcription factors , 2009, or the activation of protein kinases such as MAPK3 and MAPK6 (Beckers et al 2009), which stay inactive until pathogen recognition. Another mechanism behind priming appears to be a change in chromatin structure (Bruce et al 2007; Van den Burg and Takken 2009).…”

Stress-Responsive Mitogen-Activated Protein Kinases Interact with the EAR Motif of a Poplar Zinc Finger Protein and Mediate Its Degradation through the 26S Proteasome

“…MAPK signaling is mediated at the transcriptional, translational, and posttranslational levels (Beckers et al, 2009) and was for instance shown to promote the synthesis of camalexin, an antimicrobial compound (Ren et al, 2008). MAPKs also participate in signal transduction leading to transcriptional reprogramming of defense-related genes (Fiil et al, 2009).…”

“…Poplar MAPKs were shown to be activated in response to chitosan, ozone treatment, and following infection by Melampsora foliar rust (Hamel et al, 2005;Boyle et al, 2010), yet no downstream substrate has been identified. Based on these data, and given the importance of AtMPK3 (and its orthologs) in both the priming (Beckers et al, 2009) and regulation of defense mechanisms against bacteria and fungi (Asai et al, 2002;Ren et al, 2008), a yeast two-hybrid screen was performed to find putative interactors of poplar PtiMPK3-1. This approach allowed the identification of a novel MAPK-interacting protein, PtiZFP1, a TF that belongs to the Cys-2/His-2-type zinc finger protein family and that is characterized by the presence of an ERF-associated amphiphilic repression (EAR) motif at the C terminus.…”