L11 - Ethylene 2

Question 1

Ethylene and inter-organ relations

Answer 1

• Often ethylene production starts in one flower organ (e.g. the ovary), than ethylene may diffuse through the
  flower to other flower parts where it may stimulate further ethylene production
• Similarly, ethylene production may start in one part of a
  fruit (e.g. in the core [apple], in the gel [tomato],near
  the seed [mango])

Question 2

Ethylene receptor

Answer 2

2 component his kinase

2 identical subunits means they can transfer a phosphate group from one to another molecule

Question 3

Ethylene signal transduction components

Answer 3

2 identical sub units:

Receptor proteins in ER
Activate CTR when there is NO ethylene

Protein kinase CTR, is connected to receptor, is active when there is
NO ethylene

EIN 2 protein in ER
unstable when there is
NO ethylene

Question 4

Ethylene signalling and receptor

Answer 4

Look at schematic, slide 15 & 16

Question 5

Threshold values

Answer 5

 Dependent on:
● Temperature
● Time
● Physiological
parameters
 Typically between 0.1 and 1 ppm (100-1000ppb)

 Less effect of ethylene at low concentrations
 Less effect of ethylene at short exposure times
 Less effect of ethylene at low temperatures

Question 6

Summary (slide 21)

Answer 6

 Ethylene production is mostly determined by the activity
of ACC oxidase and ACC synthase
 Ethylene production may be autocatalytic, so a short exposure to ethylene can start the products own
production
 By blocking the receptor or signal transduction route,
autocatalysis is blocked and the response is blocked
 Ethylene effect depends on concentration and time
 Temperature is a very important determinant of ethyleneproduction and sensitivity

Question 7

Ethylene inhibition

Answer 7

1. Lowering temperature:
● Less biosynthesis
● Less interaction with receptor
● Less biological response
2. Chemical inhibitors
3. Storage under controlled atmosphere conditions
4. Removal of ethylene from atmosphere

Question 8

Chemcal inhibitors of ethylene biosynthesis and action

Answer 8

Inhibitors of:

1. ACC synthase
   - AVG (Amino ethoxy vinyl glycine)
   - AOA (Amino oxy acetid acid)
2. ACC oxidase
   AIBA (Amino isobutyric acid)
   Cobalt

3. Ethylene
KMnO4
zeolites
Ventilation
Chemical destruction

4. Receptor and signal transduction
   STS
   1-MCP ( smartfresh
   sugar

Question 9

STS

Answer 9

Mixture of Silver nitrate and Sodium
thiosulphate. Greatly improves the uptake of the silver in e.g. flowers

STS blocks abscission of petals
flowers treated with ethylene

Question 10

1-MCP (1 - methyl cyclopropene)

Answer 10

1-MCP prevents ethylene from occupying the receptor

A gas, but it is immobilized in cyclodextrins. In water, the sugar dissolves, gas is released

Question 11

1-MCP, STS and sugar lower ethylene

sensitivity and indirectly biosynthesis

Answer 11

Graph of slide 39

Question 12

Effect of Controlled Atmosphere conditions on ethylene biosynthesis and action

Answer 12

• on ACC oxidase
  Low oxygen
  (ACC oxidase is O2 dependent)
• on Receptor and signal transduction:
  Low oxygen
  High carbon dioxide
  (CO2 is an ethylene antagonist)

Question 13

Removal of ethylene

Answer 13

 Removal of ethylene from the atmosphere can also to
some extent avoid ethylene problems
 Ripe or rotten fruit produces ethylene that can stimulate
the ethylene production of the non ripe fruit
 To be effective ethylene removal should keep levels
really low because 0.1 1 ppm can already stimulate the ethylene production of unripe fruit

Question 14

Ways of removing or filtering ethylene

Answer 14

 Fresh air exchange
●
Cheap, effective, but no option in CA
 Thermocatalytic oxidation
● Pt/Pd at 200 C --> energy, hot spots
 Chemical oxidation
● Ozone --> toxic, damaging to equipment
● Aluminum oxide pellets impregnated with KMnO4
 Photocatalytic oxidation (air purification systems)

Question 15

Best way to suppress undesirable ethylene effects

Answer 15

1. Lower the temperature
2. Use controlled atmosphere storage
3. Use chemicals with proven efficacy (STS, MCP, ..)
4. Ventilate with clean air (often not possible)
5. Use air purification devices (but they do not always work)