pathogens agrobacterium tumefaciens agrobacterium rhizogenes pseudomonas syringeae pseudomonas...
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Pathogens Agrobacterium tumefaciens Agrobacterium rhizogenes Pseudomonas syringeae Pseudomonas aeruginosa Viroids DNA viruses RNA viruses Fungi oomycetes nematodes Symbionts N-fixers Endomycorrhizae Ectomycorrhizae. Mineral Nutrition Macronutrients: CHOPKNSCaFeMg - PowerPoint PPT PresentationTRANSCRIPT
Pathogens• Agrobacterium tumefaciens • Agrobacterium rhizogenes• Pseudomonas syringeae• Pseudomonas aeruginosa• Viroids• DNA viruses• RNA viruses• Fungi• oomycetes• nematodes
Symbionts• N-fixers• Endomycorrhizae• Ectomycorrhizae
Mineral NutritionMacronutrients: CHOPKNSCaFeMg
• Ca: signaling, middle lamella, cofactor• Fe: cofactor• Mg: cofactor• mobile in plant, so shows first in old leaves
Mineral NutritionMicronutrients: 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
Mineral NutritionSoil nutrients•Amounts & availability vary•Many are immobile, eg P, Fe
Mineral NutritionNutrients in soil•Plants alter pH @ roots to aid uptake• Also use symbionts
• Mycorrhizal fungi help: especially with P
Mineral NutritionAlso 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
Mineral NutritionEctomycorrhizae surround root: trees•release nutrients into apoplast to be taken up by rootsEndomycorrhizae invade root cells: Vesicular/Arbuscular
• Most angiosperms, especially in nutrient-poor soils
RhizosphereEndomycorrhizae invade root cells: Vesicular/Arbuscular
• Most angiosperms, especially in nutrient-poor soils• May deliver nutrients into symplast• Or may release them when arbuscule dies
RhizosphereEndomycorrhizae invade root cells: Vesicular/Arbuscular
• Most angiosperms, especially in nutrient-poor soils• Deliver nutrients into symplast or release them
when arbuscule diesAlso find bacteria, actinomycetes, protozoa associated with root surface = rhizosphere
RhizosphereAlso find bacteria, actinomycetes, protozoa associated with root surface = rhizosphere• Plants feed them lots of C!
RhizosphereAlso find bacteria, actinomycetes, protozoa associated with root surface = rhizosphere• Plants feed them lots of C!• They help make nutrients available
RhizosphereAlso 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
N assimilation by N fixersExclusively performed by prokaryotesDramatically improve the growth of many plants
N assimilation by N fixersExclusively done by prokaryotesMost are free-living in soil or water
N assimilation by N fixersExclusively done by prokaryotesMost are free-living in soil or waterSome form symbioses with plants
N assimilation by N fixersExclusively done by prokaryotesMost are free-living in soil or waterSome form symbioses with plantsLegumes are best-known, butmany others including mosses,ferns, lichens
N assimilation by N fixersExclusively done by prokaryotesMost are free-living in soil or waterSome form symbioses with plantsLegumes are best-known, butmany others including mosses,ferns, lichensAlso have associations where N-fixers form films on leaves orroots and are fed by plant
N assimilation by N fixersExclusively done by prokaryotesAlso have associations where N-fixers form films on leaves orroots and are fed by plantAll must form O2-free environment for nitrogenase
N assimilation by N fixersAll must form O2-free environment for nitrogenaseO2 binds & inactivates electron-transfer sites
N assimilation by N fixersO2 binds & inactivates electron-transfer sitesHeterocysts lack PSII, haveother mechs to lower O2
N assimilation by N fixersHeterocysts lack PSII, haveother mechs to lower O2 Nodules have specialstructure + leghemoglobinto protect from O2
Nodule formationNodules have special structure + leghemoglobin to protect
from O2 Bacteria induce the plant to form nodules
Nodule formationBacteria induce the plant to form nodules1. Root hairs secrete chemicals that attract N-fixers
Nodule formationBacteria induce the plant to form nodules1. Root hairs secrete chemicals that attract N-fixers2. Bacteria secrete Nod factors that induce root hair to
coil up. Nod factors determine species-specificity
Nodule formation1. Root hairs secrete chemicals that attract N-fixers2. Bacteria secrete Nod factors that induce root hair to
coil up. Nod factors determine species-specificity3. Nod factors induce degradation of root cell wall
Nodule formation3. Nod factors induce degradation of root cell wall4. Plant forms "infection thread"=internal protusion of
plasma membrane that grows into cell5. When reaches end of cell bacteria are released into
apoplast and repeat the process on inner cells
Nodule formation5. When reaches end of cell bacteria are released into
apoplast and repeat the process on inner cells6. Cortical cells near xylem form a nodule primordium
Nodule formation5. When reaches end of cell bacteria are released into
apoplast and repeat the process on inner cells6. Cortical cells near xylem form a nodule primordium7. When bacteria reach these cells the infection thread
breaks off, forming vesicles with bacteria inside
Nodule formation7. When bacteria reach these cells the infection thread
breaks off, forming vesicles with bacteria inside8. Vesicles fuse, form the peribacteroid membrane and
bacteria differentiate into bacteroids.
Nodule formation8. Vesicles fuse, form the peribacteroid membrane and
bacteria differentiate into bacteroids.9. Plant cells differentiate into nodules
Nodule formation8. Vesicles fuse, form the peribacteroid membrane and
bacteria differentiate into bacteroids.9. Plant cells differentiate into nodules: have layer of cells
to exclude O2 & vasculatureto exchange nutrients
Nodule formationPlant cells differentiate into nodules: have layer of cells to
exclude O2 & vasculature to exchange nutrientsComplex process that is difficult to engineer: 21 non-
legume plant genera have N-fixers
Nitrogen fixationN2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi
Catalysed by nitrogenase, a very complex enzyme!
Nitrogen fixationN2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi
Catalysed by nitrogenase, a very complex enzyme!Also catalyzes many other reactionsUsually assayed by acetylene reduction
Nitrogen fixationN2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi
Usually assayed by acetylene reductionSequentially adds 2 H per cycle until reach NH3
Nitrogen fixationSequentially adds 2 H per cycle until reach NH3
May then be exported to cytosol & assimilated by GS/GOGAT or assimilated inside bacteroid
Nitrogen fixationSequentially adds 2 H per cycle until reach NH3
May then be exported to cytosol & assimilated by GS/GOGAT or assimilated inside bacteroidAre then converted to amides or ureides& exported to rest of plant in the xylem!
Nutrient uptakeMost nutrients are dissolved in water
Nutrient uptakeMost nutrients are dissolved in water
• Enter root through apoplast until hit endodermis
Nutrient uptakeMost nutrients are dissolved in water
• Enter root through apoplast until hit endodermis• Then must cross plasma membrane
Crossing membranesA) Diffusion through bilayer B) Difusion through protein poreC) Facilitated diffusionD) Active transportE) Bulk transport
1) Exocytosis2) Endocytosis
Selective
Active
Nutrient uptakeThen must cross plasma membrane
• Gases, small uncharged & non-polar molecules diffuse
Nutrient uptakeThen must cross plasma membrane
• Gases, small uncharged & non-polar molecules diffusedown their ∆ [ ]• Important for CO2, auxin & NH3 transport
Nutrient uptakeThen must cross plasma membrane
• Gases, small uncharged & non-polar molecules diffusedown their ∆ [ ]• Polar chems must go through proteins!
Selective Transport1) Channelsintegral membrane proteins with pore that specific ions diffuse through
Selective Transport1) Channelsintegral membrane proteins with pore that specific ions diffuse through• depends on size & charge
Channelsintegral membrane proteins with pore that specific ions diffuse through• depends on size & charge• O in selectivity filter bindion (replace H2O)
Channelsintegral membrane proteins with pore that specific ions diffuse through• depends on size & charge• O in selectivity filter bindion (replace H2O)• only right one fits
ChannelsO in selectivity filter bindion (replace H2O)• only right one fits• driving force?electrochemical