Exploring Plant Biology: Stress Responses & Nutrition Impacts

1. Plan C • We will pick a problem in plant biology and see where it takes us. • Plant products • Climate/CO2 change • Stress responses/stress avoidance

2. Plants & products chosen • Capsaicin • Capsicum sp. • Glucosinolates • Radishes (Raphanussativus) • Mustard(Brassica juncea) • Alliin -> Allicin • Garlic (Allium sativum)

3. Other candidates • Propanethial-S-oxide • Onions (Allium cepa) • Portulacanones • Purslane(Portulacaoleracea) • Allylisothiocyanate • Horseradish (Armoraciarusticana) • Wasabi (Eutremajaponicum) • eugenol (and others) • Basil (Ocimumbasilicum)

4. Stresses Chosen • Climate change • Temperature • Increased pCO2 • Drought • pH • Nutrient deprivation • Metal toxicity (a result of low pH) • Predation • Shaking

5. Course Plan • We will study effects of nutrition and stresses on plant growth and secondary products and see where it leads us • Learn about plant stress • Learn about plant nutrition • Learn about plant secondary products • Pick plants to study • Decide how to study them

6. Plant Stress • Won Senator Proxmire’s “Golden Fleece” award for wasteful government spending • Water? • Nutrients? • Environment? • Temp? • Pollution? • Ozone, other gases? • Herbicides, eg Round-Up, Atrazine? • Insects and other herbivores? • Pathogens = bacteria, viruses, fungi

7. Mineral Nutrition • Studied by soil-free culture in nutrient solutions: • Sand culture • Hydroponics: immerse roots in nutrient solution • Slanted film maintains [nutrients] &O2 • Aeroponics spraysnutrient solution on roots

8. Mineral Nutrition Macronutrients: CHOPKNSCaFeMg Micronutrients: BNaCl others include Cu, Zn, Mn

9. Mineral Nutrition • Soil nutrients • Amounts & availabilityvary • Many are immobile, eg P, Fe

10. Mineral Nutrition • Ectomycorrhizae surround root: only trees, esp. conifers • release nutrients into apoplast to be taken up by roots

11. Rhizosphere • Endomycorrhizae invade root cells: Vesicular/Arbuscular • Most angiosperms, especially in nutrient-poor soils • Deliver nutrients into symplast or release them when arbuscule dies • Also find bacteria, actinomycetes, protozoa associated with root surface = rhizosphere

12. Rhizosphere • N-fixing bacteria supply N to many plant spp • Most live in root nodules & are fed & protected from O2 by plant

13. Nutrient uptake • Then must cross plasma membrane • Gases, small uncharged & non-polar molecules diffuse • down their ∆ [ ] • Important for CO2, auxin & NH3 transport

14. Nutrient uptake • Then must cross plasma membrane • Gases, small uncharged & non-polar molecules diffuse • down their ∆ [ ] • Polar chems must go through proteins!

15. Selective Transport 1) Channels integral membrane proteins with pore that specificionsdiffuse through

16. Selective Transport • 1) Channels • integral membrane proteins with pore that specificionsdiffuse through • depends on size • &charge

17. Channels • integral membrane proteins with pore • that specificionsdiffuse through • depends on size& charge • O in selectivity filter bind • ion (replace H2O)

18. Channels • integral membrane proteins with pore • that specificionsdiffuse through • depends on size& charge • O in selectivity filter bind • ion (replace H2O) • only right one fits

19. Channels • O in selectivity filter bind • ion (replace H2O) • only right one fits • driving force? • electrochemical D

20. Channels • driving force : electrochemical D • “non-saturable”

21. Channels • driving force : electrochemical D • “non-saturable” • regulate by opening & closing

22. Channels • regulate by opening & closing • ligand-gated channels open/close when bind specific chemicals

23. Channels • ligand-gated channels open/close when bind specific chemicals • Stress-activated channels open/close in response to mechanical stimulation

24. Channels Stress-activated channels open/close in response to mechanical stimulation voltage-gatedchannels open/close in response to changes in electrical potential

25. Channels • Old model: S4 slides up/down • Paddle model: S4 rotates

26. Channels • Old model: S4 slides up/down • Paddle model: S4 rotates • 3 states • Closed • Open • Inactivated

27. Selective Transport • 1) Channels • 2) Facilitated Diffusion (carriers) • Carrier binds molecule

28. Selective Transport • Facilitated Diffusion (carriers) • Carrier binds molecule • carries it through membrane • & releases it inside

29. Selective Transport • Facilitated Diffusion (carriers) • Carrier binds molecule • carries it through membrane • & releases it inside • driving force = ∆ [ ]

30. Selective Transport • Facilitated Diffusion (carriers) • Carrier binds molecule • carries it through membrane • & releases it inside • driving force = ∆ [ ] • Important for sugar • transport

31. Selective Transport • Facilitated Diffusion (carriers) • Characteristics • 1) saturable • 2) specific • 3) passive: transports • down ∆ []

32. Selective Transport 1) Channels 2) Facilitated Diffusion (carriers) Passive transport should equalize [ ] Nothing in a plant cell is at equilibrium!

33. Selective Transport Passive transport should equalize [ ] Nothing in a plant cell is at equilibrium! Solution: use energy to transport specific ions against their ∆ [ ]

34. Active Transport • Integral membrane proteins • use energy to transport specific ions against their ∆ [ ] • allow cells to concentrate some chemicals, exclude others

35. Active Transport Characteristics 1) saturable 105-106 ions/s 102-104 molecules/s

36. Active Transport Characteristics 1) saturable 2) specific

37. Active Transport Characteristics 1) saturable 2) specific 3) active: transport up ∆ [ ] (or ∆ Em)

38. 4 classes of Active transport ATPase proteins • 1) P-type ATPases (P = “phosphorylation”) • Na/K pump • Ca pump in ER & PM • H+ pump in PM • pumps H+ out of cell

39. 4 classes of Active transport ATPase proteins • 1) P-type ATPases (P = “phosphorylation”) • 2) V-type ATPases (V = “vacuole”) • H+ pump in vacuoles

40. 4 classes of Active transport ATPase proteins • 1) P-type ATPases (P = “phosphorylation”) • 2) V-type ATPases (V=“vacuole”) • 3) F-type ATPases (F = “factor”) a.k.a. ATP synthases • mitochondrial ATP synthase • chloroplast ATP synthase

41. 4 classes of Active transport ATPase proteins • 1) P-type ATPases (P = “phosphorylation”) • 2) V-type ATPases (V = “vacuole”) • 3) F-type ATPases (F = “factor”) • 4) ABC ATPases (ABC = “ATP Binding Cassette”) • multidrug resistance proteins

42. 4 classes of Active transport ATPase proteins • 1) P-type ATPases (P = “phosphorylation”) • 2) V-type ATPases (V = “vacuole”) • 3) F-type ATPases (F = “factor”) • 4) ABC ATPases (ABC = “ATP Binding Cassette”) • multidrug resistance proteins • pump hydrophobic drugs out of cells • very broad specificity

43. Secondary active transport Uses ∆ [ ] created by active transport to pump something else across a membrane against its ∆ [ ]

44. Secondary active transport Uses ∆ [ ] created by active transport to pump something else across a membrane against its ∆ [ ] Symport:both substances pumped same way

45. Secondary active transport Uses ∆ [ ] created by active transport to pump something else across a membrane against its ∆ [ ] Symport:both substances pumped same way Antiport: substances pumped opposite ways

46. Secondary active transport Uses ∆ [ ] created by active transport to pump something else across a membrane against its ∆ [ ] Symport:both substances pumped same way Antiport: substances pumped opposite ways

47. Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ]

48. Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically!

49. Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically! H+ is actively pumped out of cell by P-type H+ -ATPase

50. Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically! H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type!