Regulation of plant development
by ethylene
Ethylene biosynthesis
Expression analysis
of ACS
Transcriptional regulation of ACS expression
Auxin Wounding
-IAA +IAA
Mutant screens for ethylene pathway genes
airC2H4 air C2H4
Wt mutants
*
Roman et al., 1994
* phenotype rescued by inhibitor of ethylene biosynthesis
Screen for ethylene mutants
I. Genes involved in regulation of biosynthesis
eto mutants – constitutive triple response
WT eto2
-5
0
5
10
15
20
25
30
35
40
WT eto2-1
ethyleneproductionpl.mg-1
.h-1
eto2 eto3
- overproduction of ethylene
eto2,eto3 dominant mutation results from single
amino acid change in the C terminus ACS5,ACS9
eto2 mutation does not affect specific activity of ACS5
eto3 mutation does not affect level of ACS9 mRNA
Effect of eto2 mutation on
ACS5 protein stability
Posttranscritpional regulation of ACS
Eto1- recesive mutant with constitutive
triple response
ETO1 interacts with ACS5
and regulates its activity
ETO1 promotes ACS5 degradation through
proteasome dependent pathway
Model for regulation
of ethylene biosynthesis by ETO1
* *
* * *
Screen for ethylene mutants
II. Genes invoved in signalling pathway
Roman et al., 1994
*
*
*
*
Roman et al., 1994
*
Roman et al., 1994
Roman et al., 1994
Roman et al., 1994
ETR1 codes for histidine kinase
Bleecker et al.,1988 Hua et al., 1998 Sakai et al., 1998
etr1 ein4 ers2 etr2
His-kinases in Arabidopsis
Ethylene signalling
– homology to two component system ?
Ctr1 – codes for protein kinase of Raf family
ETR1 interacts with CTR1
Clark et al., 1998
CTR1 ctr1-1
CTR1 has protein kinase activity
-ethylene receptor dominant mutation > ethylene insensitivity
-ethylene receptor loss of function mutation > constitutive ethylene response
-ctr1 loss of function mutation > constitutive ethylene response
ctr1
EIN2 - contains domain similar to Nramp metal
transporters protein.
EIN3 codes for transcription factor
Chao et al., 1997
GUS::EIN3 GUS::Nla GUS
EIN3 protein level is controlled by ethylene
EIN3 is rapidly degraded by a proteasome-mediated pathway
Guo and Ecker, 2003
EIN3 accumulates in nucleus upon ethylene or MG132 treatment
EIN3 interacts with F-box proteins
Guo and Ecker, 2003
ACC MG132
Mutation in EBF1 and EBF2 results in hypersensitivity
to ethylene and accumulation of EIN3 protein
Guo and Ecker, 2003
Overexpression of EBF1 and EBF2 results in ethylene
insensitivity and reduced accumulation of EIN3 protein
Guo and Ecker, 2003
Guo and Ecker, 2003
MODELS
Ethylene signal transduction pathway
Ethylene Modulates Stem Cell Division
in roots
Olga Ortega-Martínez et al., 2007
Ethylene promotes
QC cell division.
QC cell identity and function are maintained
in eto1 mutants
Ethylene stimulates
formation of additional columella cell layers