Transcript Bio 226: Cell and Molecular Biology

Course Plan
We will study effects of soil and stresses on plant
secondary products and see where it leads us
1. Learn more about plant secondary products
• Why do they make them?
• When do they make them?
• Where do they make them?
Pick some plants to study
•Capsicum (Chiles) = capsaicin
•Nicotiana (Tobacco) = nicotine
•Onions (Allium cepa)?= syn-Propanethial-S-oxide
•Garlic (Allium sativum)?= Alliin
•Radishes (Raphanus sativus) = glucosinolates
•Mustard (Brassica juncea) = glucosinolates
•Basil (Ocimum basilicum) = eugenol (and others)
•Cilantro (Coriandrum sativum) = lots of candidates!
•Peppermint (Mentha × piperita) = menthol + many
•Catnip (Nepeta cataria) = nepetalactone
•Dill = dillapiole
•Purslane (Portulaca oleracea)= omega-3 fatty acids
•Brassica rapa = glucosinolates
Plant Stress
Won Senator Proxmire’s “Golden Fleece” award for
wasteful government spending
1.Water?
2.Nutrients?
3.Environment?
• Temp?
• Pollution?
• Ozone, other gases?
• Herbicides, eg Round-Up, Atrazine?
• Insects and other herbivores?
• Pathogens = bacteria, viruses, fungi
Plant Stress
Next assignment: presenting a plant stressor, what is
known about it, and why it might affect plant 2˚
compounds in an ~ 10 minute presentation?
Alternative: presenting another good plant/stressor
response to study and why we should choose it over the
ones already presented.
Mineral Nutrition
Macronutrients: CHOPKNSCaFeMgBNaCl
• Ca: signaling, middle lamella, cofactor
• Fe: cofactor
• Mg: cofactor
• mobile in plant, so shows first in old leaves
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
Plant food
• 2.6% ammoniacal nitrogen
• 4.4% nitrate nitrogen
• 9% phosphorus
• 5% potassium
• calcium (2%)
• magnesium (0.5%)
• sulfur (0.05%)
• boron (0.02%)
• chlorine (0.1%)
• cobalt (0.0015%)
• copper (0.05%)
• iron (0.1%)
• manganese (0.05%)
• molybdenum (0.0009%)
• nickel (0.0001%)
• sodium (0.10%)
• zinc (0.05%)
Mineral Nutrition
Soil nutrients
•Amounts & availability vary
PSU extension
Text
Mineral Nutrition
Soil nutrients
•Amounts & availability vary
•Many are immobile, eg P, Fe
Mineral Nutrition
Soil nutrients
• Amounts & availability vary
• Many are immobile, eg P, Fe
• Mobile nutrients come with soil H2O
Mineral Nutrition
Soil nutrients
• Amounts & availability vary
• Many are immobile, eg P, Fe
• Mobile nutrients come with soil H2O
• Immobiles must be “mined”
• Root hairs get close
Mineral Nutrition
Immobile nutrients must be “mined”
• Root hairs get close
• Mycorrhizae get closer
Mineral Nutrition
Immobile nutrients must be mined
• Root hairs get close
• Mycorrhizae get closer
Solubility varies w pH
Mineral Nutrition
•Solubility varies w pH
•5.5 is best compromise
Mineral Nutrition
Solubility varies w pH
•5.5 is best compromise
•Plants alter pH @ roots to
aid uptake
Mineral Nutrition
Nutrients in soil
•Plants alter pH @ roots to aid uptake
• Also use symbionts
• Mycorrhizal fungi help: especially with P
Mineral Nutrition
Also use symbionts
•Mycorrhizal fungi help: especially with P
• P travels poorly: fungal hyphae are longer & thinner
Mineral Nutrition
Also use symbionts
•Mycorrhizal fungi help: especially with P
• P travels poorly: fungal hyphae are longer & thinner
• Fungi give plants nutrients
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
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
Mineral Nutrition
Ectomycorrhizae surround root: only trees, esp. conifers
• release nutrients into apoplast to be taken up by roots
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
Mineral Nutrition
Endomycorrhizae invade root cells: Vesicular/Arbuscular
• Most angiosperms, especially in nutrient-poor soils
• May deliver nutrients into symplast
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
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
Also find bacteria, actinomycetes, protozoa associated
with root surface = rhizosphere
• Plants feed them lots of C!
Rhizosphere
Also find bacteria, actinomycetes, protozoa associated
with root surface = rhizosphere
• Plants feed them lots of C!
• They help make nutrients available
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
N assimilation by N fixers
Exclusively performed by prokaryotes
Dramatically improve the growth of many plants
N assimilation by N fixers
Exclusively done by prokaryotes
Most are free-living in soil or water
N assimilation by N fixers
Exclusively done by prokaryotes
Most are free-living in soil or water
Some form symbioses with plants
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
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
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
N assimilation by N fixers
All must form O2-free
environment for nitrogenase
O2 binds & inactivates electron
-transfer sites
N assimilation by N fixers
O2 binds & inactivates electron
-transfer sites
Heterocysts lack PSII, have
other mechs to lower O2
N assimilation by N fixers
Heterocysts lack PSII, have
other mechs to lower O2
Nodules have special
structure + leghemoglobin
to protect from O2
Nodule formation
Nodules have special structure + leghemoglobin to protect
from O2
Bacteria induce the plant to form nodules
Nodule formation
Bacteria induce the plant to form nodules
1. Root hairs secrete chemicals that attract N-fixers
Nodule formation
Bacteria induce the plant to form nodules
1. Root hairs secrete chemicals that attract N-fixers
2. Bacteria secrete Nod factors that induce root hair to
coil up. Nod factors determine species-specificity
Nodule formation
1. Root hairs secrete chemicals that attract N-fixers
2. Bacteria secrete Nod factors that induce root hair to
coil up. Nod factors determine species-specificity
3. Nod factors induce degradation of root cell wall
Nodule formation
3. Nod factors induce degradation of root cell wall
4. Plant forms "infection thread"=internal protusion of
plasma membrane that grows into cell
5. When reaches end of cell bacteria are released into
apoplast and repeat the process on inner cells
Nodule formation
5. When reaches end of cell bacteria are released into
apoplast and repeat the process on inner cells
6. Cortical cells near xylem form a nodule primordium
Nodule formation
5. When reaches end of cell bacteria are released into
apoplast and repeat the process on inner cells
6. Cortical cells near xylem form a nodule primordium
7. When bacteria reach these cells the infection thread
breaks off, forming vesicles with bacteria inside
Nodule formation
7. When bacteria reach these cells the infection thread
breaks off, forming vesicles with bacteria inside
8. Vesicles fuse, form the peribacteroid membrane and
bacteria differentiate into bacteroids.
Nodule formation
8. Vesicles fuse, form the peribacteroid membrane and
bacteria differentiate into bacteroids.
9. Plant cells differentiate into nodules
Nodule formation
8. Vesicles fuse, form the peribacteroid membrane and
bacteria differentiate into bacteroids.
9. Plant cells differentiate into nodules: have layer of cells
to exclude O2 & vasculature
to exchange nutrients
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 nonlegume plant genera have N-fixers
Nitrogen fixation
N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi
Catalysed by nitrogenase, a very complex enzyme!
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
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
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
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!
Nutrient uptake
Most nutrients are dissolved in water
Nutrient uptake
Most nutrients are dissolved in water
• Enter root through apoplast until hit endodermis
Nutrient uptake
Most nutrients are dissolved in water
• Enter root through apoplast until hit endodermis
• Then must cross plasma membrane
Crossing membranes
A) Diffusion through bilayer
B) Difusion through protein pore
Selective
C) Facilitated diffusion
D) Active transport
E) Bulk transport
Active
1) Exocytosis
2) Endocytosis
Nutrient uptake
Then must cross plasma membrane
• Gases, small uncharged & non-polar molecules diffuse
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
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
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
Na+ is also expelled
by H+ antiport
•Enters through channels
Ca2+ is expelled by P-type
ATPases in PM
& pumped into vacuole
by H+ antiport
Nutrient uptake
Na+ is also expelled
by H+ antiport
•Enters through channels
Ca2+ is expelled by P-type
ATPases in PM
& pumped into vacuole
by H+ antiport
• enters cytosol via channels
PO4, SO4, Cl & NO3
enter by H+ symport
Nutrient uptake
PO4, SO4, Cl & NO3
enter by H+ symport
• also have anion channels of ABC type