Ethylene c 2 h 4
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ETHYLENE C 2 H 4. Plant Hormone. Regulatory functions in growth and development Stimulators or inhibitors. Physiological Effects of Ethylene. Normal growth and development Stress response biotic and abiotic. Ethylene in organisms. Animal Production: not normal Effect:

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ETHYLENE C 2 H 4

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Ethylene c 2 h 4

ETHYLENEC2H4


Ethylene c2h4

Plant Hormone

Regulatory functions in

growth and development

Stimulators or inhibitors


Ethylene c2h4

Physiological Effects of Ethylene

Normal growth and development

Stress response

biotic and abiotic


Ethylene c2h4

Ethylene in organisms

Animal

Production: not normal

Effect:

82+ % as anesthetic in 15 second

ignition at humidity lower than 56 %


Ethylene c2h4

Ethylene in organisms

Bacteria

Bacterial rot of cauliflower

Fungi

Pennicilium digitatum

Aspergillus flavus

Alternaria solani


Ethylene c2h4

Ethylene in organisms

Neljubov(1901):

Gaseous hydrocarbon olefin

Triple response in etiolated pea seedlings

Cousins (1910):

Orange and banana in the same shipment


Ethylene c2h4

Gane(1934):

Ethylene as a natural plant product


Ethylene c2h4

Ethylene Diffusibility

Easily released from tissues

Diffuse through the gas phase

intercellular and outside

Rapid and sensitive response system

Active concentration:10 ppb


Ethylene c2h4

Ethylene

Biosynthetic

Pathway

(1979)


Ethylene c2h4

Alternative pathway

Peroxidation of

long chain fatty acids

eg. Linolenic acid


Ethylene c2h4

Met SAM ACC Ethylene

N-Malonyl ACC

(Nonvolatile compound)


Ethylene c2h4

Synthesized in most tissues of

almost all higher plants

Easily isolated and quantified

Also found in gymnosperms

lower plants

bacteria


Ethylene c2h4

Ethylene Production

Environmental effect

* O2 O2 C2H4 (except rice)

* Temperature

apple T P

peanut / plum T P

* CO2

appleP

sweet potatoP

beanno effect


Ethylene c2h4

Ethylene Production

Other hormones

Auxin: activate production: 10x

GA:activate in bean citrus blueberry

inhibit in soybean seedling

CK: activate in bean blueberry sorghum

ABA: activate in leaf and fruit

inhibit in seed and soybean seedling


Ethylene c2h4

Enzymes in Ethylene Biosynthetic Pathway


Ethylene c2h4

ACC Synthase or ACCS

Rate-limiting step of pathway

SAM to ACC

ACCS level

Hormone levels

Growth environment

Physiological environment

Developmental environment


Ethylene c2h4

ACC Synthase or ACCS

Amino acid sequences of

tomato, apple, squash and zucchini

Share 40% identity and 80% similarity

Contain 7 highly conserved regions


Ethylene c2h4

ACC Synthase or ACCS

Different isoforms

Encoded by a multigene family


Ethylene c2h4

ACC oxidase or ACCO

Require aerobic conditions

ACC to Ethylene

ACCO level:

environmental stresses


Ethylene c2h4

ACC oxidase or ACCO

Ethylene-forming enzyme : EFE

A ripening-induced cDNA

confers yeast an oxidase activity


Ethylene c2h4

ACC-N-Malonyl transferase

ACCM

Autoregulation to prevent

ethylene overproduction

Storage / inactive form of ACC


Ethylene c2h4

Ethylene transport

Diffusion (short distance)

ACC (long distance)


Ethylene c2h4

Ethylene metabolism

oxidation and hydrolysis

Ethylene oxide

ethylene glycol

Glucose conjugates of ethylene glycol

CO2


Ethylene c2h4

Ethylene Action

CS2 a potent inhibitor

of ethylene oxidation

No effect on ethylene responses

Action of ethylene ……..?


Ethylene c2h4

*Ethylene effects

not general for all plants

*A signal of environmental changes

or physiological changes


Ethylene c2h4

*Manifold effects mediated by

induction of new proteins

*regulator or

modulator or

coordinator of processes


Ethylene c2h4

Ethylene

Perception by receptors

Signal transduction

Responses


Ethylene c2h4

Ethylene binding

Ethylene receptors

Hypothesis

Reversibly binding to a receptor

through a transition metal


Ethylene c2h4

Ethylene-binding components

Membrane bound

Solubility

Chromatographic behaviors

Sensitive toheat

protease

sulfhydryl agent

Nature of protein


Ethylene c2h4

Ethylene-binding proteins (EBP):

Various tissues and plants

tobacco, bean, Arabidopsis

Specific

High affinity

Saturable

Characteristics of receptor

binding moiety facing the apoplast


Ethylene c2h4

Ethylene binding protein

EBP of Phaseolus vulgaris

Heterotrimer or

Heterotetramer

Subunits of ca. 12 to 14 kDa

Integral membrane protein


Ethylene c2h4

ETR

Receptor found in Arabidopsis

Dimer

Subunits of 79 to 83 kDa

3 transmembrane segments


Ethylene c2h4

Classes of ethylene-binding proteins

- High rate constant of

association/dissociation

- Very low rate constant of

association/dissociation


Ethylene c2h4

Classes of ethylene-binding proteins

2 classes

rice tomato

pea Arabidopsis

Class 2:

bean (Phaseolus)

mungbean


Ethylene c2h4

Ethylene-insensitive mutant

Arabidopsis

Decreased ethylene binding

Low concentrations of

ethylene binding protein


Ethylene c2h4

Antibody against Phaseolus EBP

Recognize homologous proteins

from pea

rice

Arabidopsis


Ethylene c2h4

Signal transduction pathway

Signaling pathway

A two-component system

bacteria

common / well-characterized

key mechanism

protein phosphorylation


Ethylene c2h4

2-component signaling pathway

Histidine kinase for

sensing / transducing

extracellular signals


Ethylene c2h4

2-component signaling pathway

Phosphotransfer between

two types of signal transducers

Sensory kinase

(input & kinase domains)

Response regulator

(receiver & output domains)


Ethylene c2h4

Ethylene signal transduction pathway

Genetic and biochemical studies

Similar to a bacterial two-component system

Conserved residues for kinase activity in EBP

Phosphorylation of EBP upon binding of ethylene


Ethylene c2h4

Ethylene

kinase

Response

regulator

P

P

ATP

Response

Model for regulation

of ethylene action


Ethylene c2h4

  • Ethylene binding

  • Autophosphorylation of kinase

  • Phosphate transfer to a response regulator

  • Release of an activated ligand or

  • activation of soluble factor

  • Derepression of genes involved in

  • ethylene responses


Ethylene c2h4

Model of ethylene signal transduction

RAN1

Cu

ETR1 ETR2 EIN4

ERS1 ERS2

Air

CTR1

EIN2

EIN3

OFF


Ethylene c2h4

Model of ethylene signal transduction

RAN1

Cu

ETR1 ETR2 EIN4

ERS1 ERS2

C2H4

CTR1

EIN2

ON

EIN3


Ethylene c2h4

Model of ethylene signal transduction


Ethylene c2h4

Regulation of ethylene

synthesis and activity

Activated by

high auxin

fruit ripening

flower senescence

wounding

chilling injury

drought

ACCS


Ethylene c2h4

Regulation of ethylene

synthesis and activity

Inhibited by

ABA

ethylene

AVG

AOA

ACCS


Ethylene c2h4

Regulation of ethylene

synthesis and activity

Activated by

ripening

senescence

ethylene

ACCO


Ethylene c2h4

Regulation of ethylene

synthesis and activity

Inhibited by

anaerobiosis

Co2+

high temp (35+)

ACCO


Ethylene c2h4

Regulation of ethylene

synthesis and activity

Ethylene level : Metabolism / Environment

Silver ion

CO2 (high conc at 3 to 5%)

NBD (2,5-norbornadiene)

DACP (diazo-cyclopentadiene)

Cyclic olefins

Cis butene

Ethylene binding


Ethylene c2h4

Commercial uses of ethylene

- Ethylene- Acetylene - ACC

- Ethylene-releasing compounds

Ethephon / Ethrel

*******************************************

- Ventilation with hypobaric pressure

- Silver- AVG / AOA- KMnO4


Ethylene c2h4

Ethylene / cell expansion / triple response

thicker and shorter Root/hypocotyl

reorientation of cell expansion


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