Ethylene and Senescence Matt Mckechnie

Properties Hormone Structure only gas of the five classic plant hormones Structure hydrocarbon

Historical facts Ancient Egypt fig gashing Ancient China burned incense to ripen pears Neljubow (1901) coal lamps Cousins (1910) oranges Gane (1934) natural product Burg & Thimann (1959) quantification McKeon et al. (1995) biosynthetic pathway

Functions Stimulates bromelliad, pineapple flower induction Induction of femaleness in flowers Stimulates flower opening Stimulates fruit ripening Stimulates the release of dormancy. Stimulates shoot and root growth and differentiation (triple response) May have a role in adventitious root formation Stimulates leaf and fruit abscission

Senescence Plants age productively because as tissues senesce they produce enzymes necessary to recycle valuable materials and reroute the subunits to areas for use by active growth in some other place, at some other time or in the next generation

Biosynthesis of ethylene from methionine from the Yang cycle to AdoMet -while consuming 1 ATP to ACC (limiting step) via ACC synthase to ethylene via ACC oxidase

Senescence-mechanism Hormonal response Climacteric Protein synthesis For limited/controlled hydrolysis Transport To seeds, active growth areas or storage

Controlling Senescence cytokinins and gibberellins seeds, roots High [CO2] Limits respiration Harsh Chemicals (florists) Antifungal agents-sodium benzoate Anti-ethylene agents (silver nitrate)

Detecting Ethylene Quantitatively Gas chromatography sensitive down to parts per trillion

Detecting Ethylene Qualitatively Bioassays for best results: triple response in pea seedlings other bioassays epinasty of tomato leaves root hair formation leaf abscission

Associated research SAGs response vs. different stresses and hormone treatments ethylene detached leaves in the dark were most affected Indicated by older and younger leaves reacting similarly four new SAGs were isolated