Stress responses/stress avoidance 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

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

Other candidates Propanethial-S-oxide Onions (Allium cepa) Portulacanones Purslane (Portulaca oleracea) Allyl isothiocyanate Horseradish (Armoracia rusticana) Wasabi (Eutrema japonicum) eugenol (and others) Basil (Ocimum basilicum)

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

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

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

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

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

Mineral Nutrition Soil nutrients Amounts & availability vary Many are immobile, eg P, Fe

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

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

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

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

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

Selective Transport 1) Channels integral membrane proteins with pore that specific ions diffuse through

Selective Transport 1) Channels integral membrane proteins with pore that specific ions diffuse through depends on size & charge

Channels integral membrane proteins with pore that specific ions diffuse through depends on size & charge O in selectivity filter bind ion (replace H2O)

Channels integral membrane proteins with pore that specific ions diffuse through depends on size & charge O in selectivity filter bind ion (replace H2O) only right one fits

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

Channels driving force : electrochemical D “non-saturable”

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

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

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

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

Channels Old model: S4 slides up/down Paddle model: S4 rotates 3 states Closed Open 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

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

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

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

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 105-106 ions/s 102-104 molecules/s

Active Transport Characteristics 1) saturable 2) specific

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 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!

Nutrient uptake H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type! 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! Main way plants make membrane potential (∆Em)! K+ diffuses through channels down ∆Em

Nutrient uptake K+ diffuses through channels down ∆Em Also taken up by transporters

Nutrient uptake K+ diffuses through channels down ∆Em Also taken up by transporters some also transport Na+

Nutrient uptake K+ diffuses through channels down ∆Em Also taken up by transporters some also transport Na+ why Na+ slows K+ uptake?

Nutrient uptake K+ diffuses through channels down ∆Em Also taken up by transporters some also transport Na+ why Na+ slows K+ uptake? Na+ is also expelled by H+ antiport

Nutrient uptake K+ diffuses through channels down ∆Em Also taken up by transporters some also transport Na+ why Na+ slows K+ uptake? Na+ is also expelled by H+ antiport Enters through channels

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- & NO3- enter by H+ symport

Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport also have anion transporters 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- & tri- 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- & tri- peptides 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- & tri- peptides 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- & tri- peptides 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

Nutrient assimilation Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd)

Nutrient assimilation Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e-

Nutrient assimilation Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e- Nitrogen fixation costs 16 ATP + 8 e-

Nutrient assimilation Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e- Nitrogen fixation costs 16 ATP + 8 e- SO42- reduction to S2- costs 8 e- + 2ATP

Nutrient assimilation Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e- Nitrogen fixation costs 16 ATP + 8 e- SO42- reduction to S2- costs 8 e- + 2ATP S2- assimilation into Cysteine costs 2 more e- Most explosives are based on N or S!