2 Until 1964, ethylene was though to derive from ETHYLENE ORIGINATING FROM LIPIDS?Until 1964, ethylene was though to derive fromthe enzymatic disruption of lipids involvingfree radicals formationArguments:-Oxygen is required for the biosynthesis ofethylene in plants;-Free radical scavengers (antioxidants thatprevent lipid oxidation, e.g. propyl gallate ...)inhibited ethylene production.
3 DISCOVERY OF METHIONINE AS A PRECURSOR OF ETHYLENE * *MethionineNH3+CH3-S-CH2-CH2-CH-COO-DISCOVERY OF METHIONINEAS A PRECURSOR OF ETHYLENELieberman and Mapson, 1964
4 OTHER INHIBITORS OF ETHYLENE SYNTHESIS Lieberman and Owens, 1971CH2-CH-CH2-O-C=C-CH-COOHOH NH H NH2HRhizobitoxine from Rhizobium japonicumCH2-CH2-CH2-O-C=C-CH-COOHNH H NH2HAVG= Amino ethoxy vinyl glycine from Streptomyces
5 Shang-Fa YANGDISCOVERY OF ACC AND METHIONINE CYCLE« Knight of Roquetaillade », Ethylene Congress Agen, 1992
6 Radio-chromatograms of ethylene extracts of apple plugs 14C-MethionineRadio-chromatograms ofethylene extracts of appleplugsPlugs in air, 12hPlugs in N2, 6hPlugs in N2, 6hthen in air, 6h
21 Inhibitors of ACC synthase: Rhizobitoxine, AVG EFFECTORS OF ACC SYNTHASE AND ACC OXIDASEInhibitors of ACC synthase: Rhizobitoxine, AVGFactors stimulating ACS gene expression:Auxins, chilling, wounding, drought, pathogens,ethyleneInhibitors of ACC oxidase: Anoxia, uncouplers,free radical scavengers, Co++, Ni++, T°>35°C,Factors stimulating ACO gene expression:Pathogens, ethylene, wounding
22 ACC SYNTHASE GENE FAMILY IN ARABIDOPSIS At-ACS5 [induced by Li, cycloheximide(CH) and lowconcentration of cytokinin(CK)]At-ACS4 (induced by CH, IAA and wounding)At-ACS1At-ACS2Le-ACS2Le-ACS4At-ACS6Le-ACS6Le-ACS1ALe-ACS1BAt-ACS7At-ACS11Le-ACS5At-ACS4At-ACS8At-ACS5At-ACS9Le-ACS7Le-ACS3Le-ACS8At-ACS10At-ACS12Branch IBranch IIBranch III*At-ACS1 (induced by cycloheximide)At-ACS10 in response to light in plants overexpressing CONSTANSAt-ACS8 not yetcharacterizedAt-ACS2 in young leaves and flowersAt-ACS6 (induced by O3, Cu2+, IAA, CH, CN-, anaerobiosis, wounding, touching and ethylene)At-ACS4 (induced by CH, IAA, anaerobisisand wounding)At-ACS7 (induced by CH)At-ACS5 (basallevel stimulatedby Li and CKAt-ACS2 (induced by Li, CH, wounding)At-ACS4 induced by CH, IAA, wounding)At-ACS9 = eto1Adult plantEtiolated seedling
23 ACO AND ACS GENE EXPRESSION IN TOMATO FLOWERLe-ACS2 (stamens, mature and senescent anthers)Le-ACO2Le-ACS2 (senescent petals)Le-ACO4Le-ACO1, 3Le-ACS3 (not expressed in fruit, present in tomato cell suspension)Le-ACO3 (breaker stage)Le-ACS4 induced by woundingLe-ACO4Le-ACS2 and 4 positiv. regul. by ethyleneLe-ACO1,2,3 and 4induced by O3Le-ACS1A (breaker stage) negativ. regul. by ethyleneLe-ACS6 (in MG fruit) negativ. regul. by ethyleneLe-ACS7 induced early by woundingLe-ACO1 in senescentor wounded leavesLe-ACS3 induced by floodingLe-ACS7 induced early by flooding
24 Regulation of ethylene biosynthetic genes ACC synthaseArabidopsis Rapidly induced by auxin (ACS4).Induced by low levels of cytokinin (ACS5).Rumex Flood resistant species downregulates ACS,flood sensitive does not.Rice Enzyme activity induced by hypoxia/flooding.Mung bean Induced by mechanical stress (AIM1).Tomato Induced by fruit ripening.Induced by flooding (ACS3).Induced by ozone (ACS2).Phaseolus Induced by auxin (ACS1).Synergistic induction with auxin (ACS2).Winter squash Induced by auxin (accA).Induced by wounding (accW).Phalaenopsis Induced by ethylene (ACS1)Induced in stigma after pollination or auxin treatment(ACS1, ACS2).Induced in ovary after pollination or auxin treatment(ACS3).Carnation Late induction by ethylene, pollination inducesexpression after hours in petals (CARACC3).Stellaria Regulated by photoperiod.Potato Rapidly induced by ozone, infection and Cu2+ (ACS5).Slowly induced by ozone, infection and Cu2+ (ACS4).Zucchini Induced by wounding and auxin only in fruit (ACC1A).ACC oxidaseArabidopsis Induced by ethylene (ACO2/E1305).Tomato ACO1 antisense transgenic plants have reducedethylene production and epinasty after flooding.Induced during flower development (ACO1-3).Induced by wounding (ACO1).Induced during senescence (ACO, ACO3).Phalaenopsis Induced by ethylene.Unpollinated flowers cannot convert ACC toethylene.Cantaloupe Induced by ethylene, wounding, NaCl, drought andripening (ACO1).Induced by NaCl and drought (ACO3).Petunia Induced by ethylene (ACO3).Induced in senescing floral organs (ACO1, ACO3).Induced in developing pistils (ACO3, ACO4).Winter Squash Induced by wounding, induction blocked by ethyleneinhibitor, endogenous ethylene accelerates induction.Carnation Induced by pollination in styles and petals (SR120).Mung bean Induced by ethylene(ACO1, ACO2).Peach Induced by wounding and fruit ripening.Apple Induced during fruit ripening.Broccoli Induced after harvest (ACC Ox1).Induced in reproductive organs postharvest(ACC Ox2).