Ethylene

I. Overview

• Gas hormone (C2H4)
• Citrus growers and kerosene heaters/ fruit ripening
• bioassay for the triple response

II. Chemistry

• synthesized from Methionine
• ACC
• ACC oxidase produces ethylene
• requires oxygen
• not conjugated
• catabolized to ethylene oxide or CO2

III. Conditions of production

• flooding
• senescence
• wounding
• drought stress
• IAA--some effects of auxin are actually ethylene

IV. Physiological effects

• effective @ 1ul/L
• Abscission
  • reduces auxin transport
  • seperation layer
• Flooding
  • transport of ACC
  • no O2 in roots for ethylene production
• Fruit Ripening
  • climacteric fruits: examples
  • respiratory burst
  • ACC first then ethylene
  • targets cell wall softening
  • cellulase in avocado
  • ethephon: synthethic ethylene
    • synchronize ripening
    • conditions slow ripening: high CO2/cool temperatures/low O2

V. Mode of action

• ethylene receptor
• membrane protein
• activates transcription
• model from handout