Ethylene

Question 1

Ethylene discovery

Answer 1

As a component of coal gas

High level in ripening fruit, young developing leaves, damaged/wounded tissue

Question 2

Ethylene physiological effect

Answer 2

Fruit ripening- Climacteric ripening (apple, banana, pear, tomato) and autocatalytic ripening.

Epinasty- Downward curvature of leaves because of flooded roots.
Hypoxia induces ACC synthase ethylene production,

Root hairs formation: Treatment of
seedlings with increasing
concentrations of the ethylene
precursor, ACC results in
progressively more root hair cells
developing in positions normally
occupied by non-hair cells.

Senescence: aging in plants, inhibitors of ethylene synthesis delay it

Abscission: Shedding leaves regulated by auxin. 3 phases: leaf maintenance (high auxin levels), abscission induction phase (reduction of auxin and increase of ethylene), abscission phase

Lateral cell expansion: Bioassay

Question 3

Ethylene biosynthesis promotion and inhibitors

Answer 3

Fruit ripening causes an increase in ACC oxidase and ACC synthase activity.

Stress-induced ethylene production
induced by drought, chilling, wounding, flooding: results from an increase in ACC synthase production.

Auxin-induced ethylene production
induction of flowering in pineapple;
inhibition of stem elongation.
Some responses once attributed to auxin are ethylene
responses

inhibitors: Ag+ and CO2

Question 4

Ethylene Bioassay

Answer 4

A triple response: thickened and shorter stem, apical hook exaggeration. It is good for determining presence but not quantitative. Thought to help seedlings push past impediments for germinated dark, impeded seedlings

Question 5

Ethylene Mutants

Answer 5

etr1-1 mutation (dominant): The receptor for ethylene response is always off whether there is a presence or not. Similar to cytokinin receptors.

ctr1 mutant: the kinase activity is disrupted, leading to a constitutive triple response even without ethylene.

Question 6

Ethylene Signaling

Answer 6

Ethylene binding deactivates the receptor molecules, and in the absence of a positive regulatory signal from the receptors, the CTR1 protein becomes inactive. Further
transduction of the ethylene signal
requires positive regulators that
function downstream of CTR1.
EIN2 is an integral-membrane
protein. Downstream of EIN2 is the
EIN3 family of transcription factors,
these bind to the EBS element in
the promoter of the ERF1 gene and
activate its expression in an
ethylene dependent manner