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

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Presentation on theme: "ABIOTIC STRESSES REDIRECT PROTEIN SYNTHESIS Mikal E. Saltveit Mann Laboratory, Department of Vegetable Crops University of California, Davis."— Presentation transcript:

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

2 Participants in this research M.E. Mangrich J.G. Loaiza-Velarde F.A. Tomás-Barberán M.A. Ritenour A. Rab M. Cantwell G. Peiser G. López-Gálvez

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

4 Wounding The Stimulus Wounding Increased PAL Activity Produces the Physiological Response Increased PAL Activity Tissue Browning Resulting in Tissue Browning

5 Lettuce leaf tissue CUT Signal

6 CUT PAL Lettuce leaf tissue

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

8 Time Relative values Wound signal PAL activity PAL inactivating factor Phenolic compounds

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

13 Absorbance at 320 nm/g sec

14 How does heat-shock reduce subsequent browning in lettuce?

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

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21 Application of a heat-shock after wounding

22 Hours after wounding PAL activity Control HS after 8 h HS after 1 h HS after 24 h

23 Application of a heat-shock before wounding

24 Woundedcontrol HS -4 h, W W, HS +2 h W, HS +2 h, W +6 h Hours after wounding PAL activity

25 Wounded Unwounded control Heat-shocked Hours before wounding PAL activity Wounded 50 °C, 90 sec Held at 5 °C

26 It’s not the proteins that are synthesized but the synthesis of the proteins that protects against browning

27 Protein synthesis “Normal” General

28 “Normal” General Wounding Signal PAL

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

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

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

33 It appears that one stress (heat (heat shock) 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 Chilling temperatures Membrane phase change Secondary effects Primary effect Primary cause Increased membrane permeabilityInflux of calcium Depolymerization of microtubulesReduced photosynthesis Protoplasmic streaming stopsAltered enzyme activity Toxic metabolites accumulateAltered metabolism Symptoms Accelerated senescenceIncreased decay Increased water lossVascular browning Abnormal ripeningTissue discoloration Increased ethylene productionElevated 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 Accumulated toxins Chilling injury Heat-shock HSPs

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

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

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

41 Chilling temperatures Primary effects Membranes Microtubules Proteins Pathways Primary effects Secondary effects Increased membrane permeability Influx of calcium Depolymerization of microtubulesProtoplasmic streaming stops Altered enzyme activityAltered metabolism Reduced photosynthesisToxic metabolites accumulate Primary cause Accelerated senescence and decay Increased water loss Tissue discoloration Abnormal ripening Increased ethylene productionElevated respiration Symptoms

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

43 ETHYLENE SYNTHESIS Methionine SAM ACC C 2 H 4 ACC Synthase ACC Oxidase MACC Fruit ripening Flower senescence Auxin, Wounding Chilling, Drought Flooding + AVG, AOA - Ripening, Ethylene Anaerobiosis Cobalt, > 35 °C Free radical scavengers + - (CO 2, O 2 )

44 Hierarchical Response to abiotic stresses  Heat-shock  Wounding  Non-stressed ?  Drought  Anaerobic  Salt  UV

45 Participants in this research M.A. Mangrich F.A. Tomás-Barberán J.G. Loaiza-Velarde M.A. Ritenour A. Rab M. Cantwell G. Peiser G. López-Gálvez


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