MAP KINASE PHOSPHATASE1 and PROTEIN TYROSINE PHOSPHATASE1 Are Repressors of Salicylic Acid Synthesis and SNC1-Mediated Responses inArabidopsis   

Abstract

Mitogen-activated protein (MAP) kinase phosphatases are important negative regulators of the levels and kinetics of MAP kinase activation that modulate cellular responses. The dual-specificity phosphatase MAP KINASE PHOSPHATASE1 (MKP1) was previously shown to regulate MAP KINASE6 (MPK6) activation levels and abiotic stress responses in Arabidopsis thaliana. Here, we report that the mkp1 null mutation in the Columbia (Col) accession results in growth defects and constitutive biotic defense responses, including elevated levels of salicylic acid, camalexin, PR gene expression, and resistance to the bacterial pathogen Pseudomonas syringae. PROTEIN TYROSINE PHOSPHATASE1 (PTP1) also interacts with MPK6, but the ptp1 null mutant shows no aberrant growth phenotype. However, the pronounced constitutive defense response of the mkp1 ptp1 double mutant reveals that MKP1 and PTP1 repress defense responses in a coordinated fashion. Moreover, mutations in MPK3 and MPK6 distinctly suppress mkp1 and mkp1 ptp1 phenotypes, indicating that MKP1 and PTP1 act as repressors of inappropriate MPK3/MPK6-dependent stress signaling. Finally, we provide evidence that the natural modifier of mkp1 in Col is largely the disease resistance gene homolog SUPPRESSOR OF npr1-1, CONSTITUTIVE 1 (SNC1) that is absent in the Wassilewskija accession. Our data thus indicate a major role of MKP1 and PTP1 in repressing salicylic acid biosynthesis in the autoimmune-like response caused by SNC1.

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

“…The MAP kinase kinase4 (MKK4) is known to activate MPK3 and MPK6 (Asai et al, 2002;Kim et al, 2011). Next, we transformed cells with constitutive active MKK4 EE to activate downstream MAP kinases MPK3 and MPK6 (Bartels et al, 2009) together with either the wild type or Ser309Ala mutant of HSFA4A, which led to a steady increase of pHSP17.6A-LUC transactivation reaching about 18-fold increase upon 40 h with the wild type but was around 50% less with the Ser-309Ala mutant form of HSFA4A (Fig. 9C).…”

Recent Advances in Calcium/Calmodulin-Mediated Signaling with an Emphasis on Plant-Microbe Interactions

“…Moreover, Ca 2+ /CaM binds to plant catalase and enhances its activity (Yang and Poovaiah, 2002b). Recently, Ca 2+ /CaM was also reported to regulate H 2 O 2 -mediated defense responses by regulating the MAPK cascade through the action of MAPKs and MAPK phosphatases (Lee et al, 2008;Bartels et al, 2009;Takahashi et al, 2011).…”

Phosphorylation of Arabidopsis MAP Kinase Phosphatase 1 (MKP1) Is Required for PAMP Responses and Resistance against Bacteria

“…Consistent with enhanced PAMP responses, the mkp1 mutant also displayed enhanced resistance to the virulent pathogen Pseudomonas syringae pv tomato DC3000 (hereafter referred to as DC3000). The enhanced PAMP-induced growth inhibition and resistance in mkp1 are specifically dependent on MPK6, indicating a genetic interaction between MKP1 and MPK6 (Bartels et al, 2009;Anderson et al, 2011). Because of the importance of these negative regulators in modulating defense responses, it is also critical to understand how phosphatases such as MKP1 are regulated.…”

“…However, the regulation of MKPs during PAMP responses in plants is not well understood. Both in vitro and in vivo studies have shown that Arabidopsis MKP1 interacts with three MAPKs (MPK3, MPK4, and MPK6), with the strongest interaction being with MPK6 (Ulm et al, 2002;Bartels et al, 2009). In addition, Arabidopsis MKP1 was shown to be phosphorylated in vitro by MPK6, and phosphorylation increased the phosphatase activity of MKP1, indicating that phosphorylation may be an important regulatory mechanism of MKP1 (Park et al, 2011).…”