1. §5　Ethylene

2. I: Discovery of ethylene as a plant hormone
the Chinese may have been the first to observe the effects of ethylene when they noted that burning incense increased fruit ripening
in 1864 leaks in gas lights in street lamps were reported to stunt plant growth and defoliate trees
1901 Neljubow in St. Petersburg Russia found Triple-response of pea seedlings: dwarf stem, fat stem, agravitropism in stem. Identified ethylene from the gas as the causative agent.

3. 1910 Cousin found rippen oranges cause bananas to ripen prematurely
1934 Gane found Ethylene is a natural product (plant hormone?) from apple.
Forgotten for many years as possible hormone....
1959 Burg & Thimann rediscovered old research and begin studies showing ethylene as possible hormone (GC technique)

4. II: structure of ethylene

5. III: Distribution and synthesis
Distributed in almost all organs of higher plants, in particular in mature organs such as rippen fruits depending on the stage of development. The content is less than 0.1ppm
Synthesized from Met (methionine) by Lieberman and Mapson in 1964 and elucidated by Dr. Yang and Adams in 1977.

6. biosynthesis
SAM
synthetase
ACC synthase
(SAM)
PP22011.jpg

7. AOA: aminooxyacetic acid 氨基氧乙酸； AVG: aminoethoxy vinyl
Ripen等
AOA and AVG
stresses
Co2+, DNP等
SAM
(ACC)
AOA: aminooxyacetic acid
氨基氧乙酸；
AVG: aminoethoxy vinyl
glycine acid: 氨基乙氧基
乙烯基甘氨酸
PP22012.jpg

8. Regulation of Eth synthesis
ACC synthase: triggered by senescence, drought, flooding, wounding, IAA, chilling
ACC oxidase: triggered by ripening, O2, inhibited by Co2+, DNP
ACC can be conjugated to form MACC (thus reduce Eth level)

9. IV: Functions of Eth
Triple response: In etiolated seedlings, Eth causes the inhibition of hypocotyl elongation,
a pronounced radial swellings of the hypocotyls, and exaggerated curvature of the plumular hook(胚芽钩）.

10. 2. Promote fruit ripening
CONTROL
ETHYLENE

11. Changes during the ripening of apples.
Ethylene promotes ripening and is produced during ripening.
Ethylene is autocatalytic
PP22020.jpg

12. The respiratory climacteric of bananas is associated with a spike of ethylene production.
PP22040.jpg

13. 3: promote senescence and abscission
Control
Eth (from apple)

14. Eth induces cellulase and pectinase in abscission layer

15. 4: induction of adventitious roots under flooding
CONTROL
ETHYLENE

17. 5. Stimulates pineapple flower induction
6. Induction of femaleness in dioecious flowers (same to IAA)
7. Enhancement of secondary metabolite production such as rubber latex

18. Mechanism of Eth function
Receptor of Ethylene has been identified –ETR-1, a homogeneous dimer with 2 domains: one for binding Eth and another for signal transduction.

19. Action model of Eth

20. Usage of Eth
Ethylene is not utilized in agriculture because its gaseous phase, instead, Ethephon, a liquid, and gives off ethylene when pH>4.1, is widely used in treating immature fruits.

21. Anti-Eth Strategies Antisense RNA of ACC synthase gene
Antisense RNA of ACC oxidase gene
Insertion of etr-1 gene
Chemical inhibition：Ag++2S2O32- →[Ag(S2O3)2]3-

22. Left: fruits from tomatoes inserted antisense ACC-oxidase gene, stored for 3 weeks after the onset of ripening.
Right: wild type fruits

23. Ag+ blocks endogenous ethylene action