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Pathogens • Agrobacterium tumefaciens: Greg • Agrobacterium rhizogenes • Pseudomonas syringeae • Pseudomonas aeruginosa: Mike • Viroids: Bryant • DNA viruses • RNA viruses: Rob • Fungi • oomycetes • Nematodes: Chris Symbionts • N-fixers • Endomycorrhizae • Ectomycorrhizae Nutrient uptake Most nutrients are dissolved in water • Enter root through apoplast until hit endodermis • Then must cross plasma membrane Nutrient uptake Then must cross plasma membrane • Gases, small uncharged & non-polar molecules diffuse down their ∆ [ ] • Important for CO2, auxin & NH3 transport Selective Transport 1) Channels integral membrane proteins with pore that specific ions diffuse through Channels driving force : electrochemical D “non-saturable” regulate by opening & closing Channels Stress-activated channels open/close in response to mechanical stimulation voltage-gated channels open/close in response to changes in electrical potential Channels • Old model: S4 slides up/down • Paddle model: S4 rotates • 3 states 1.Closed 2.Open 3. Inactivated Selective Transport 1) Channels 2) Facilitated Diffusion (carriers) Carrier binds molecule Selective Transport Facilitated Diffusion (carriers) Carrier binds molecule carries it through membrane & releases it inside Selective Transport Facilitated Diffusion (carriers) Carrier binds molecule carries it through membrane & releases it inside driving force = ∆ [ ] Selective Transport Facilitated Diffusion (carriers) Carrier binds molecule carries it through membrane & releases it inside driving force = ∆ [ ] Important for sugar transport Active Transport Integral membrane proteins • use energy to transport specific ions against their ∆ [ ] • allow cells to concentrate some chemicals, exclude others Active Transport Characteristics 1) saturable 2) specific 3) active: transport up ∆ [ ] (or ∆ Em) 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 4 classes of Active transport ATPase proteins 1) P-type ATPases (P = “phosphorylation”) 2) V-type ATPases (V = “vacuole”) • H+ pump in vacuoles 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 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 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 Secondary active transport Uses ∆ [ ] created by active transport to pump something else across a membrane against its ∆ [ ] Secondary active transport Uses ∆ [ ] created by active transport to pump something else across a membrane against its ∆ [ ] Symport: both substances pumped same way 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 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 Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically! Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically! H+ is actively pumped out of cell by P-type H+ -ATPase Nutrient uptake Ions vary dramatically! H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type ATPase & PPase Nutrient uptake H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type ATPase & PPase • Main way plants make membrane potential (∆Em)! Nutrient uptake H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type ATPase & PPase • Main way plants make membrane potential (∆Em)! • Used for many kinds of transport! Nutrient uptake Many ions are imported by multiple transporters with varying affinities Nutrient uptake Many ions are imported by multiple transporters with varying affinities • K+ diffuses through channels down ∆Em: low affinity Nutrient uptake Many ions are imported by multiple transporters with varying affinities • K+ diffuses through channels down ∆Em: low affinity • Also taken up by H+ symporters : high affinity Nutrient uptake Many ions are imported by multiple transporters with varying affinities • K+ diffuses through channels down ∆Em: low affinity • Also taken up by H+ symporters : high affinity • Low affinity is cheaper but less effective Nutrient uptake K+ diffuses through channels down ∆Em: low affinity Also taken up by H+ symporters : high affinity Low affinity is cheaper but less effective some channels also transport Na+ Nutrient uptake K+ diffuses through channels down ∆Em: low affinity Also taken up by H+ symporters : high affinity Low affinity is cheaper but less effective some channels also transport Na+ why Na+ slows K+ uptake? Nutrient uptake K+ diffuses through channels down ∆Em: low affinity Also taken up by H+ symporters : high affinity Low affinity is cheaper but less effective some channels also transport Na+ why Na+ slows K+ uptake? Na+ is also expelled by H+ antiport Nutrient uptake Na+ is also expelled by H+ antiport •Enters through channels Ca2+ is expelled by P-type ATPases in PM Nutrient uptake Ca2+ is expelled by P-type ATPases in PM & pumped into vacuole & ER by H+ antiport & P-type Nutrient uptake Ca2+ is expelled by P-type ATPases in PM pumped into vacuole & ER by H+ antiport & P-type • enters cytosol via gated channels Nutrient uptake PO43-, SO42-, Cl- & NO3enter by H+ symport Nutrient uptake PO4, SO4, Cl & NO3 enter by H+ symport • also have anion channels of ABC type Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport • also have anion transporters of ABC type • and anion channels Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport • also have anion transporters of ABC type • and anion channels Plants take up N many ways Nutrient uptake Plants take up N many ways: NO3- & NH4+ are main forms Nutrient uptake Plants take up N many other ways • NO3- also by channels • NH3 by diffusion • NH4+ by carriers Nutrient uptake Plants take up N many other ways • NO3- by channels • NH3 by diffusion • NH4+ by carriers • NH4+ by channels Nutrient uptake Plants take up N many other ways • 3 families of H+ symporters take up amino acids Nutrient uptake Plants take up N many other ways •3 families of H+ symporters take up amino acids •Also have many peptide transporters • some take up di- & tripeptides by H+ symport Nutrient uptake Plants take up N many other ways •3 families of H+ symporters take up amino acids •Also have many peptide transporters • some take up di- & tripeptides by H+ symport • others take up tetra- & penta-peptides by H+ symport Nutrient uptake Plants take up N many other ways •3 families of H+ symporters take up amino acids •Also have many peptide transporters • some take up di- & tripeptides by H+ symport • others take up tetra- & penta-peptides by H+ symport Also have ABC transporters that import peptides Nutrient uptake Plants take up N many other ways •3 families of H+ symporters take up amino acids •Also have many peptide transporters • some take up di- & tripeptides by H+ symport • others take up tetra- & penta-peptides by H+ symport Also have ABC transporters that import peptides N is vital! NO3- & NH4+ are main forms Nutrient uptake Metals are taken up by ZIP proteins & by ABC transporters • same protein may import Fe, Zn & Mn! Nutrient uptake Much is coupled to pH gradient Nutrient transport in roots Move from soil to endodermis in apoplast Nutrient transport in roots Move from soil to endodermis in apoplast Move from endodermis to xylem in symplast Nutrient transport in roots Move from endodermis to xylem in symplast Transported into xylem by H+ antiporters Nutrient transport in roots Move from endodermis to xylem in symplast Transported into xylem by H+ antiporters, channels Nutrient transport in roots Transported into xylem by H+ antiporters, channels,pumps Nutrient transport in roots Transported into xylem by H+ antiporters, channels,pumps Lowers xylem water potential -> root pressure Water Transport Passes water & nutrients to xylem Ys of xylem makes root pressure Causes guttation: pumping water into shoot Transport to shoot Nutrients move up plant in xylem sap Nutrient transport in leaves Xylem sap moves through apoplast Leaf cells take up what they want