Abstract
In plants, ethylene gas functions as a potent endogenous growth regulator. In the model system Arabidopsis thaliana, the molecular mechanisms that underlie perception and transduction of the ethylene signal to the nucleus, where the transcription of hundreds of genes is altered, are being elucidated. In the current view, ethylene is sensed by a family of five receptors that show similarity to the bacterial two-component histidine kinases, and in plants function as negative regulators of the pathway. Binding of the ethylene gas turns off the receptors, resulting in the inactivation of another negative regulator of ethylene signaling, CTR1, a Raf-like protein kinase that directly interacts with the receptors. EIN2, a protein of unknown biochemical activity that functions as a positive regulator of the pathway, acts downstream of CTR. Derepression of EIN2 by ethylene upon disabling of the receptors and CTR1 leads to the activation of EIN3 and EIN3-like transcription factors. In the absence of ethylene, the levels of EIN3 protein are extremely low because of the function of two F-box-containing proteins, EBF1 and EBF2, that target EIN3 for proteosome-mediated degradation. In the presence of ethylene, the EIN3 protein accumulates in the nucleus and initiates a transcriptional cascade, resulting in the activation and repression of hundreds of genes. To date, the only empirically demonstrated direct target of EIN3 is the APETALA2 (AP2)-domain-containing transcription factor gene ERF1. The coregulation of ERF1 by another plant hormone, jasmonic acid, illustrates how a transcriptional cascade could be utilized in a combinatorial fashion to generate a large diversity of responses using a limited number of input signals. As new components and points of intersection with other pathways are identified, the Connections Map will be updated.
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Claims 4
Claim · model-written summary
In Arabidopsis, the ethylene receptor family acts as negative regulators of the ethylene signalling pathway.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Gene
- a family of five receptorse2
- Outcome
- negative regulators of the pathwaye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the model system Arabidopsis thaliana”
e2“ethylene is sensed by a family of five receptors that show similarity to the bacterial two-component histidine kinases, and in plants function as negative regulators of the pathway”
Claim · model-written summary
Ethylene-induced derepression of EIN2 leads to activation of EIN3 and EIN3-like transcription factors in Arabidopsis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- ethylenee3
- Gene
- EIN2e3
- Outcome
- activation of EIN3 and EIN3-like transcription factorse3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the model system Arabidopsis thaliana”
e3“Derepression of EIN2 by ethylene upon disabling of the receptors and CTR1 leads to the activation of EIN3 and EIN3-like transcription factors”
Claim · model-written summary
EBF1 and EBF2 target EIN3 for proteasome-mediated degradation in Arabidopsis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- EBF1 and EBF2e4
- Outcome
- proteosome-mediated degradatione4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the model system Arabidopsis thaliana”
e4“two F-box-containing proteins, EBF1 and EBF2, that target EIN3 for proteosome-mediated degradation”
Claim · model-written summary
ERF1 is the only empirically demonstrated direct target of EIN3 in Arabidopsis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- ERF1e5
- Outcome
- direct target of EIN3e5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the model system Arabidopsis thaliana”
e5“the only empirically demonstrated direct target of EIN3 is the APETALA2 (AP2)-domain-containing transcription factor gene ERF1”