Pathogens Agrobacterium tumefaciens Agrobacterium rhizogenes Pseudomonas syringeae Pseudomonas aeruginosa Viroids DNA v

1. Pathogens • Agrobacterium tumefaciens • Agrobacterium rhizogenes • Pseudomonas syringeae • Pseudomonas aeruginosa • Viroids • DNA viruses • RNA viruses • Fungi • oomycetes • nematodes • Symbionts • N-fixers • Endomycorrhizae • Ectomycorrhizae

2. Mineral Nutrition • Macronutrients: CHOPKNSCaFeMg • Ca: signaling, middle lamella, cofactor • Fe: cofactor • Mg: cofactor • mobile in plant, so shows first in old leaves

3. Mineral Nutrition • Micronutrients: BNaCl others include Cu, Zn, Mn • B: cell elongation. NA metabolism • Na: PEP regeneration, K substitute • Cl: water-splitting, osmotic balance • Cu: cofactor • immobile in plant, so shows first in young leaves

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

5. Mineral Nutrition • Nutrients in soil • Plants alter pH @ roots toaid uptake • Also use symbionts • Mycorrhizal fungi help: especially with P

6. Mineral Nutrition • Also use symbionts • Mycorrhizal fungi help: especially with P • P travels poorly: fungal hyphae are longer & thinner • Fungi give plants nutrients • Plants feed them sugar • Ectomycorrhizae surround root: only trees, esp. conifers

7. Mineral Nutrition • Ectomycorrhizae surround root: trees • release nutrients into apoplast to be taken up by roots • Endomycorrhizae invade root cells: Vesicular/Arbuscular • Most angiosperms, especially in nutrient-poor soils

8. Rhizosphere • Endomycorrhizae invade root cells: Vesicular/Arbuscular • Most angiosperms, especially in nutrient-poor soils • May deliver nutrients into symplast • Or may release them when arbuscule dies

9. 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

10. Rhizosphere • Also find bacteria, actinomycetes, protozoa associated with root surface = rhizosphere • Plants feed them lots of C!

11. Rhizosphere • Also find bacteria, actinomycetes, protozoa associated with root surface = rhizosphere • Plants feed them lots of C! • They help make nutrients available

12. Rhizosphere • Also find bacteria, actinomycetes, protozoa associated with root surface = rhizosphere • Plants feed them lots of C! • They help make nutrients available • N-fixing bacteria supply N to many plant spp

13. N assimilation by N fixers Exclusively performed by prokaryotes Dramatically improve the growth of many plants

14. N assimilation by N fixers • Exclusively done by prokaryotes • Most are free-living in soil or water

15. N assimilation by N fixers Exclusively done by prokaryotes Most are free-living in soil or water Some form symbioses with plants

16. N assimilation by N fixers Exclusively done by prokaryotes Most are free-living in soil or water Some form symbioses with plants Legumes are best-known, but many others including mosses, ferns, lichens

17. N assimilation by N fixers Exclusively done by prokaryotes Most are free-living in soil or water Some form symbioses with plants Legumes are best-known, but many others including mosses, ferns, lichens Also have associations where N-fixers form films on leaves or roots and are fed by plant

18. N assimilation by N fixers Exclusively done by prokaryotes Also have associations where N-fixers form films on leaves or roots and are fed by plant All must form O2-free environment for nitrogenase

19. N assimilation by N fixers All must form O2-free environment for nitrogenase O2 binds & inactivates electron -transfer sites

20. N assimilation by N fixers O2 binds & inactivates electron -transfer sites Heterocysts lack PSII, have other mechs to lower O2

21. N assimilation by N fixers Heterocysts lack PSII, have other mechs to lower O2 Nodules have special structure + leghemoglobin to protect from O2

22. Nodule formation Nodules have special structure + leghemoglobin to protect from O2 Bacteria induce the plant to form nodules

23. Nodule formation Bacteria induce the plant to form nodules Root hairs secrete chemicals that attract N-fixers

24. Nodule formation Bacteria induce the plant to form nodules Root hairs secrete chemicals that attract N-fixers Bacteria secrete Nod factors that induce root hair to coil up. Nod factors determine species-specificity

25. Nodule formation Root hairs secrete chemicals that attract N-fixers Bacteria secrete Nod factors that induce root hair to coil up. Nod factors determine species-specificity Nod factors induce degradation of root cell wall

26. Nodule formation Nod factors induce degradation of root cell wall Plant forms "infection thread"=internal protusion of plasma membrane that grows into cell When reaches end of cell bacteria are released into apoplast and repeat the process on inner cells

27. Nodule formation When reaches end of cell bacteria are released into apoplast and repeat the process on inner cells Cortical cells near xylem form a nodule primordium

28. Nodule formation When reaches end of cell bacteria are released into apoplast and repeat the process on inner cells Cortical cells near xylem form a nodule primordium When bacteria reach these cells the infection thread breaks off, forming vesicles with bacteria inside

29. Nodule formation When bacteria reach these cells the infection thread breaks off, forming vesicles with bacteria inside Vesicles fuse, form the peribacteroid membrane and bacteria differentiate into bacteroids.

30. Nodule formation Vesicles fuse, form the peribacteroid membrane and bacteria differentiate into bacteroids. Plant cells differentiate into nodules

31. Nodule formation Vesicles fuse, form the peribacteroid membrane and bacteria differentiate into bacteroids. Plant cells differentiate into nodules: have layer of cells to exclude O2 & vasculature to exchange nutrients

32. Nodule formation Plant cells differentiate into nodules: have layer of cells to exclude O2 & vasculature to exchange nutrients Complex process that is difficult to engineer: 21 non-legume plant genera have N-fixers

33. Nitrogen fixation N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi Catalysed by nitrogenase, a very complex enzyme!

34. Nitrogen fixation N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi Catalysed by nitrogenase, a very complex enzyme! Also catalyzes many other reactions Usually assayed by acetylene reduction

35. Nitrogen fixation N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi Usually assayed by acetylene reduction Sequentially adds 2 H per cycle until reach NH3

36. Nitrogen fixation Sequentially adds 2 H per cycle until reach NH3 May then be exported to cytosol & assimilated by GS/GOGAT or assimilated inside bacteroid

37. Nitrogen fixation Sequentially adds 2 H per cycle until reach NH3 May then be exported to cytosol & assimilated by GS/GOGAT or assimilated inside bacteroid Are then converted to amides or ureides & exported to rest of plant in the xylem!

38. Nutrient uptake • Most nutrients are dissolved in water

39. Nutrient uptake • Most nutrients are dissolved in water • Enter root through apoplast until hit endodermis

40. Nutrient uptake • Most nutrients are dissolved in water • Enter root through apoplast until hit endodermis • Then must cross plasma membrane

41. Crossing membranes • A) Diffusion through bilayer • B) Difusion through protein pore • C) Facilitated diffusion • D) Active transport • E) Bulk transport • 1) Exocytosis • 2) Endocytosis Selective Active

42. Nutrient uptake • Then must cross plasma membrane • Gases, small uncharged & non-polar molecules diffuse

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

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

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

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

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

48. 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

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