MAPK signaling in plant hormone ethylene signal transduction

Abstract

The signal transduction pathway of the plant stress and defense hormone, ethylene, has been extensively elucidated using the plant genetic model Arabidopsis over the last two decades. Among others, a MAPKKK CTR1 was identified as a negative regulator that has led to the speculation of MAPK involvement in ethylene signaling. However, it remained unclear how the MAPK modules acting downstream of the receptors to mediate ethylene signaling. We have recently presented new evidence that the MKK9-MPK3/6 modules identified by combined functional genomic and genetic screens mediate ethylene signaling, which is negatively regulated by the genetically identified CTR1-dependent cascades. Our genetic studies show consistently that the MKK9-MPK3/MPK6 modules act downstream of the ethylene receptors. Biochemical and transgenic analyses further demonstrated that the positive-acting and negative-acting MAPK activities are integrated and act simultaneously to control the key transcription factor EIN3 through dual phosphorylations to regulate the EIN3 protein stability and downstream transcription cascades. This study has revealed a novel molecular mechanism that defines the specificity of complex MAPK signaling. Comprehensive elucidation of MAPK cascades and the underlying molecular mechanisms would provide more precise explanations for how plant cells utilize MAPK cascades to control specific downstream outputs in response to distinct stimuli.

ETHYLENE RESPONSE FACTOR6 Acts as a Central Regulator of Leaf Growth under Water-Limiting Conditions in Arabidopsis

“…A similar mechanism was recently shown to occur during oxidative stress, where ERF6 is phosphorylated by two mitogen-activated protein kinases (MPK3 and MPK6; Wang et al, 2013). Both kinases act downstream of ACC and independently of the EIN2 signaling pathway (Yoo and Sheen, 2008), and we have previously demonstrated their presence during very early osmotic stress (Skirycz et al, 2011a). Importantly, MPK3 and MPK6 were recently shown to physically interact with ERF5 and ERF6, and phosphorylation of ERF5 and ERF6 by MPK3 and MPK6 could be demonstrated (Popescu et al, 2009;Son et al, 2012;Wang et al, 2013).…”

Inverse modulation of the energy sensor Snf1‐related protein kinase 1 on hypoxia adaptation and salt stress tolerance in Arabidopsis thaliana

“…a), but it down‐regulated AtMYC2 accumulation through direct protein–protein interaction (Figs a,b,d & b). Protein stability is often under the regulation of its phosphorylation (Craig & Tyers ; Yoo & Sheen ; Yoo et al . ).…”

Role of Protein Tyrosine Phosphatases in Plants

“…The phytohormone auxin is considered as one of the key regulator of plant growth and development. It was observed that phytohormone auxin (synthetic auxin; 2,4-D) and cytokinin (kinetin) caused a higher degree of Tyr phosphorylation in Arabidopsis hypocotyls [ 85 ]. On the basis of sequence similarity, IBR5, encoding a putative DSP like protein in Arabidopsis was found as a positive regulator of both auxin and ABA [ 86 ].…”