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. 2018 Feb 22;9:114. doi: 10.3389/fpls.2018.00114

FIGURE 2.

FIGURE 2

Overview of the ethylene signaling pathway in Arabidopsis thaliana. (A) In the absence of ET, and, in the endoplasmic reticulum, ET receptors activate the CTR1 kinase that, consequently, phosphorylates EIN2, which becomes inactive and does not induce the ET response. (B) In the presence of ET, the ET receptors bind to ET and lose their CTR1-inducing activity, which in turn leads to a diminished activation of CTR1 and, consequently, the activation of EIN2. In this way, the C terminal domain of EIN2 is cleaved and migrates to the nucleus where it induces the expression of EIN3/EIL1 transcription factors, and, subsequently, ERFs and ET-responsive genes containing EBS (EIN3-binding sequences) in their promoter regions. Arrows indicate activation, and T-bars indicate repression of the pathway. Thick arrows represent a strong activation of CTR1 by the ET receptors; Dashed arrows denote less signaling activation of CTR1 upon ET binding to the receptors.