EIN2, the central regulator of ethylene signalling, is localized at the ER membrane where it interacts with the ethylene receptor ETR1

Abstract

Genetic studies have identified the membrane protein EIN2 (ethylene insensitive 2) as a central component of ethylene signalling in Arabidopsis. In addition, EIN2 might take part in multiple hormone signalling pathways and in response to pathogens as demonstrated by recent genetic and biochemical studies. Here we show, by an integrated approach using in vivo and in vitro fluorescence techniques, that EIN2 is localized at the ER (endoplasmic reticulum) membrane where it shows specific interaction with the ethylene receptor protein ETR1.

Activation of ethylene signaling is mediated by nuclear translocation of the cleaved EIN2 carboxyl terminus

“…A previous study demonstrated that EIN2 transiently expressed in tobacco leaf cells was localized at the ER membrane [4]. Our above results indicate that CEND is partly located in the nucleus, which is essential for its function.…”

“…EIN2 encodes a 1 294 amino acid protein that comprises a membrane-spanning amino terminus and a functionally unknown carboxyl terminus [3]. EIN2 was reported to localize at the ER membrane when transiently expressed in tobacco leaf cells [4]. EIN3 (ETHYLENE INSENSITIVE3) and its homolog EIL1 (EIN3-LIKE1) are two nuclear-localized transcription factors genetically acting downstream of EIN2 [5,6].…”

Differential Control of Ethylene Responses byGREEN-RIPEandGREEN-RIPE LIKE1Provides Evidence for Distinct Ethylene Signaling Modules in Tomato

“…ETHYLENE-INSENSITIVE2 (EIN2) acts genetically downstream of the ethylene receptors and CTR1 and encodes a protein with homology to the natural resistance-associated macrophage protein family of metal ion transporters (Roman et al, 1995;Alonso et al, 1999). EIN2 is localized within the ER, where it interacts with the kinase domain of each receptor in an ethylenedependent manner (Alonso et al, 1999;Bisson et al, 2009;Bisson and Groth, 2010). Phosphorylation of EIN2 by CTR1 retains EIN2 within the ER but ethylenedependent dephosphorylation leads to proteolytic cleavage of EIN2, resulting in translocation of the EIN2 C terminus into the nucleus, where it activates EIN3 and ethylene-dependent transcription (Qiao et al, 2012).…”

Overexpression of DWARF AND LESION FORMATION 1 (DLE1) causes altered activation of plant defense system in Arabidopsis thaliana

“…The ER, where DLE1 1-50 (the N-terminal part of DLE1) fused to GFP localized, plays an important role in the signal transduction of ethylene. This is because there is an ethylene receptor, ETR1, and important proteins for the signaling pathway through ETR1 in the ER membrane (Bisson et al 2009;Grefen et al 2008). A possible model is that DLE1 serves as an activator of the defense response induced by ethylene in the ER in Arabidopsis, because ethylene-dependent signal transduction is plant specific.…”

“…The transmembrane domain of ETR1, which functions as a link between the ER and Golgi apparatus, also includes an ethylene-binding site Rodriguez et al 1999). Ethylene binds to ETR1 and causes a close interaction between this receptor and ETHYLENE INSENSITIVE (EIN) 2, which is also an ER membrane protein and one of the central components of ethylene signaling at the ER membrane (Alonso et al 1999;Bisson et al 2009). …”