ETHYLENE C 2 H 4

1. ETHYLENEC2H4

2. Plant Hormone Regulatory functions in growth and development Stimulators or inhibitors

3. Physiological Effects of Ethylene Normal growth and development Stress response biotic and abiotic

4. Ethylene in organisms Animal Production: not normal Effect: 82+ % as anesthetic in 15 second ignition at humidity lower than 56 %

5. Ethylene in organisms Bacteria Bacterial rot of cauliflower Fungi Pennicilium digitatum Aspergillus flavus Alternaria solani

6. Ethylene in organisms Neljubov(1901): Gaseous hydrocarbon olefin Triple response in etiolated pea seedlings Cousins (1910): Orange and banana in the same shipment

7. Gane(1934): Ethylene as a natural plant product

8. Ethylene Diffusibility Easily released from tissues Diffuse through the gas phase intercellular and outside Rapid and sensitive response system Active concentration: 10 ppb

9. Ethylene Biosynthetic Pathway (1979)

10. Alternative pathway Peroxidation of long chain fatty acids eg. Linolenic acid

11. Met SAM ACC Ethylene N-Malonyl ACC (Nonvolatile compound)

12. Synthesized in most tissues of almost all higher plants Easily isolated and quantified Also found in gymnosperms lower plants bacteria

13. Ethylene Production Environmental effect * O2 O2 C2H4 (except rice) * Temperature apple T P peanut / plum T P * CO2 apple P sweet potato P bean no effect

14. Ethylene Production Other hormones Auxin: activate production: 10x GA: activate in bean citrus blueberry inhibit in soybean seedling CK: activate in bean blueberry sorghum ABA: activate in leaf and fruit inhibit in seed and soybean seedling

15. Enzymes in Ethylene Biosynthetic Pathway

16. ACC Synthase or ACCS Rate-limiting step of pathway SAM to ACC ACCS level Hormone levels Growth environment Physiological environment Developmental environment

17. ACC Synthase or ACCS Amino acid sequences of tomato, apple, squash and zucchini Share 40% identity and 80% similarity Contain 7 highly conserved regions

18. ACC Synthase or ACCS Different isoforms Encoded by a multigene family

19. ACC oxidase or ACCO Require aerobic conditions ACC to Ethylene ACCO level: environmental stresses

20. ACC oxidase or ACCO Ethylene-forming enzyme : EFE A ripening-induced cDNA confers yeast an oxidase activity

21. ACC-N-Malonyl transferase ACCM Autoregulation to prevent ethylene overproduction Storage / inactive form of ACC

22. Ethylene transport Diffusion (short distance) ACC (long distance)

23. Ethylene metabolism oxidation and hydrolysis Ethylene oxide ethylene glycol Glucose conjugates of ethylene glycol CO2

24. Ethylene Action CS2 a potent inhibitor of ethylene oxidation No effect on ethylene responses Action of ethylene ……..?

25. *Ethylene effects not general for all plants *A signal of environmental changes or physiological changes

26. *Manifold effects mediated by induction of new proteins *regulator or modulator or coordinator of processes

27. Ethylene Perception by receptors Signal transduction Responses

28. Ethylene binding Ethylene receptors Hypothesis Reversibly binding to a receptor through a transition metal

29. Ethylene-binding components Membrane bound Solubility Chromatographic behaviors Sensitive to heat protease sulfhydryl agent Nature of protein

30. Ethylene-binding proteins (EBP): Various tissues and plants tobacco, bean, Arabidopsis Specific High affinity Saturable Characteristics of receptor binding moiety facing the apoplast

31. Ethylene binding protein EBP of Phaseolus vulgaris Heterotrimer or Heterotetramer Subunits of ca. 12 to 14 kDa Integral membrane protein

32. ETR Receptor found in Arabidopsis Dimer Subunits of 79 to 83 kDa 3 transmembrane segments

33. Classes of ethylene-binding proteins - High rate constant of association/dissociation - Very low rate constant of association/dissociation

34. Classes of ethylene-binding proteins 2 classes rice tomato pea Arabidopsis Class 2: bean (Phaseolus) mungbean

35. Ethylene-insensitive mutant Arabidopsis Decreased ethylene binding Low concentrations of ethylene binding protein

36. Antibody against Phaseolus EBP Recognize homologous proteins from pea rice Arabidopsis

37. Signal transduction pathway Signaling pathway A two-component system bacteria common / well-characterized key mechanism protein phosphorylation

38. 2-component signaling pathway Histidine kinase for sensing / transducing extracellular signals

39. 2-component signaling pathway Phosphotransfer between two types of signal transducers Sensory kinase (input & kinase domains) Response regulator (receiver & output domains)

40. Ethylene signal transduction pathway Genetic and biochemical studies Similar to a bacterial two-component system Conserved residues for kinase activity in EBP Phosphorylation of EBP upon binding of ethylene

41. Ethylene kinase Response regulator P P ATP Response Model for regulation of ethylene action

42. Ethylene binding • Autophosphorylation of kinase • Phosphate transfer to a response regulator • Release of an activated ligand or • activation of soluble factor • Derepression of genes involved in • ethylene responses

43. Model of ethylene signal transduction RAN1 Cu ETR1 ETR2 EIN4 ERS1 ERS2 Air CTR1 EIN2 EIN3 OFF

44. Model of ethylene signal transduction RAN1 Cu ETR1 ETR2 EIN4 ERS1 ERS2 C2H4 CTR1 EIN2 ON EIN3

45. Model of ethylene signal transduction

46. Regulation of ethylene synthesis and activity Activated by high auxin fruit ripening flower senescence wounding chilling injury drought ACCS

47. Regulation of ethylene synthesis and activity Inhibited by ABA ethylene AVG AOA ACCS

48. Regulation of ethylene synthesis and activity Activated by ripening senescence ethylene ACCO

49. Regulation of ethylene synthesis and activity Inhibited by anaerobiosis Co2+ high temp (35+) ACCO

50. Regulation of ethylene synthesis and activity Ethylene level : Metabolism / Environment Silver ion CO2 (high conc at 3 to 5%) NBD (2,5-norbornadiene) DACP (diazo-cyclopentadiene) Cyclic olefins Cis butene Ethylene binding