ABIOTIC STRESSES REDIRECT PROTEIN SYNTHESIS

1. ABIOTIC STRESSESREDIRECT PROTEIN SYNTHESIS Mikal E. Saltveit Mann Laboratory, Department of Vegetable Crops University of California, Davis

2. Participants in this researchM.E. MangrichJ.G. Loaiza-VelardeF.A. Tomás-Barberán M.A. RitenourA. RabM. Cantwell G. Peiser G. López-Gálvez

3. Cause and Effect Occur in a Linear Order! A Stimulus ProducesA Physiological Response

4. The StimulusWounding Produces the Physiological ResponseIncreased PAL Activity Resulting inTissue Browning

5. CUT Lettuce leaf tissue Signal Signal

6. CUT Lettuce leaf tissue PAL PAL

7. Wound Tissue browning Signal PPO Receptor Receptor POD Cellular membranes Increased permeability DNA DNA mRNA mRNA Preexisting phenolics Vacuole Protein synthesis Protein synthesis Phenylpropanoid metabolism Phenolics PAL-IF PAL

8. PAL activity Phenolic compounds Wound signal 100 80 PAL inactivating factor Relative values 60 40 20 0 Time

12. Iceberg lettuce Cut and washed Heat-shock Held at 5 °C in 95% RH Periodically assayed for PAL and phenolic compounds

13. 0.28 0.24 0.20 0.16 60 sec Absorbance at 320 nm/g 0.12 0.08 0.04 0.00 20 30 40 50 60 70

14. How doesheat-shockreduce subsequent browning in lettuce?

15. Wounded (24 h) ~ 6x 45 °C 50 °C 120 sec 90 sec 55 °C 60 sec Control (0 h)

19. -1

20. -1

21. Application of a heat-shock after wounding

22. 0.4 0.3 Control HS after 24 h PAL activity 0.2 HS after 8 h 0.1 HS after 1 h 0 0 5 10 15 20 25 30 35 40 Hours after wounding

23. Application of a heat-shock before wounding

24. 0.16 0.14 Wounded control 0.12 0.10 PAL activity 0.08 0.06 0.04 HS -4 h, W W, HS +2 h, W +6 h 0.02 W, HS +2 h 0.00 0 5 10 15 20 25 30 35 40 Hours after wounding

25. 0.12 Wounded 0.10 0.08 0.06 PAL activity 0.04 Heat-shocked Unwounded control 50 °C, 90 sec 0.02 0.00 -40 -35 -30 -25 -20 -15 -10 -5 0 5 Hours before wounding Wounded Held at 5 °C

26. It’s not theproteins that are synthesized but the synthesis of the proteins thatprotects against browning

27. General Protein synthesis “Normal”

28. General Wounding Signal Protein synthesis PAL “Normal”

29. General Heat-shock “Signal” Protein synthesis Heat-shock proteins “Normal”

30. Could the linear sequence of metabolic events induced by one stress (e.g., wounding) be redirected by another abiotic stress (e.g., heat-shock)?

31. General Heat-shock Wounding “Signal” Signal Protein synthesis Heat-shock proteins PAL “Normal”

32. Wounding (e.g., of lettuce) Signal Normal conditions Heat-shock PAL X Synthesis of HSPs Phenolics accumulate Recovery from the heat-shock and resumption of normal protein synthesis Browning No wound signal remaining Few phenolic compounds present Very little browning

33. It appears that one stress (heat shock) can redirect and modify the response of another stress (wounding)

34. Chilling Injury is Another Stress that is Thought to Occur Through a Linear Sequence of Events

35. Primary cause Chilling temperatures Primary effect Membrane phase change Secondary effects Increased membrane permeability Influx of calcium Depolymerization of microtubules Reduced photosynthesis Protoplasmic streaming stops Altered enzyme activity Toxic metabolites accumulate Altered metabolism Symptoms Accelerated senescence Increased decay Increased water loss Vascular browning Abnormal ripening Tissue discoloration Increased ethylene production Elevated respiration

36. Does Their Synthesis Prevent the Synthesis of an Agent Causing Chilling Injury? Do Heat-shock Proteins Protect Against Chilling Injury? or

37. Chilling temperatures Abnormal metabolism Heat-shock Accumulated toxins HSPs Chilling injury

38. Chilling temperatures Abnormal metabolism Heat-shock Accumulated toxins HSPs Chilling injury No chilling injury

39. Chilling temperatures Abnormal metabolism Heat-shock Accumulated toxins Chilling injury

40. Chilling temperatures Abnormal metabolism HSPs Heat-shock Accumulated toxins No accumulated toxins Chilling injury No chilling injury

41. Primary cause Chilling temperatures Primary effects Primary effects Primary effects Membranes Proteins Microtubules Pathways Secondary effects Secondary effects Increased membrane permeability Influx of calcium Depolymerization of microtubules Protoplasmic streaming stops Altered enzyme activity Altered metabolism Reduced photosynthesis Toxic metabolites accumulate Symptoms Accelerated senescence and decay Increased water loss Tissue discoloration Abnormal ripening Increased ethylene production Elevated respiration

42. Stress-Induced Ethylene Production is Another Response that Occurs Through a Linear Sequence of Events

43. ETHYLENE SYNTHESIS Methionine SAM Fruit ripening Flower senescence Auxin, Wounding Chilling, Drought Flooding ACC Synthase + MACC ACC - ACC Oxidase (CO2, O2 ) + AVG, AOA Ripening, Ethylene - C2 H4 Anaerobiosis Cobalt, > 35 °C Free radical scavengers

44. Hierarchical Response toabiotic stresses • Heat-shock • Wounding • Non-stressed • Drought • Anaerobic • Salt • UV ?

45. Participants in this researchM.A. MangrichF.A. Tomás-BarberánJ.G. Loaiza-VelardeM.A. RitenourA. RabM. Cantwell G. Peiser G. López-Gálvez