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Water uptake Path starts at root hairs Must take water from soil Ease depends on availability & how tightly it is bound Binding depends on particle size & chem
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Water uptake Availability depends on amount in soil pores Saturation: completely full Field capacity: amount left after gravity has drained excess Permanent wilting point: amount where soil water potential is too negative for plants to take it up
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Plant Stress Water? Nutrients? Environment? Temp? Pollution? Ozone, other gases? Herbicides, eg Round-Up, Atrazine? Insects and other herbivores? Pathogens = bacteria, viruses, fungi Salinity
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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.
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Mineral Nutrition Nutrients in soil Plants alter roots to aid uptake Also use symbionts Mycorrhizal fungi help: especially with P Some plants form symbioses with N-fixing prok.
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Nutrient uptake Most nutrients are dissolved in water Enter root through apoplast until hit endodermis Then must cross plasma membrane
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Nutrient uptake Then must cross plasma membrane Gases, small uncharged & non-polar molecules diffuse down their ∆ [ ] Important for CO2, auxin & NH3 transport
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Selective Transport 1) Channels integral membrane proteins with pore that specific ions diffuse through
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Selective Transport 1) Channels 2) Facilitated Diffusion (carriers) Carrier binds molecule
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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
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Secondary active transport
Uses ∆ [ ] created by active transport to pump something else across a membrane against its ∆ [ ]
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Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically!
![Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically!](http://slideplayer.com./slide/9342978/28/images/15/Nutrient+uptake+Gases+enter%2Fexit+by+diffusion+down+their+%E2%88%86+%5B+%5D+Ions+vary+dramatically%21.jpg "Nutrient uptake Gases enter/exit by diffusion down their ∆ [ ] Ions vary dramatically!")
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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.](http://slideplayer.com./slide/9342978/28/images/16/Nutrient+uptake+Gases+enter%2Fexit+by+diffusion+down+their+%E2%88%86+%5B+%5D+Ions+vary+dramatically..jpg "H+ is actively pumped out of cell by P-type H+ -ATPase.")
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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
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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)!
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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!
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Nutrient uptake Many ions are imported by multiple transporters with varying affinities
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Nutrient uptake Many ions are imported by multiple transporters with varying affinities K+ diffuses through channels down ∆Em: low affinity
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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
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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
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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+
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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?
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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
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Nutrient uptake Na+ is also expelled by H+ antiport Enters through channels Ca2+ is expelled by P-type ATPases in PM
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Nutrient uptake Ca2+ is expelled by P-type ATPases in PM & pumped into vacuole & ER by H+ antiport & P-type
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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
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Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport
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Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport also have anion transporters of ABC type
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Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport also have anion transporters of ABC type and anion channels
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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
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Nutrient uptake Plants take up N many ways: NO3- & NH4+ are main forms
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Nutrient uptake Plants take up N many other ways NO3- also by channels NH3 by diffusion NH4+ by carriers
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Nutrient uptake Plants take up N many other ways NO3- by channels NH3 by diffusion NH4+ by carriers NH4+ by channels
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Nutrient uptake Plants take up N many other ways 3 families of H+ symporters take up amino acids
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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
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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
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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
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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
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Nutrient uptake Metals are taken up by ZIP proteins & by ABC transporters same protein may import Fe, Zn & Mn!
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Nutrient uptake Much is coupled to pH gradient
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Nutrient transport in roots
Move from soil to endodermis in apoplast
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Nutrient transport in roots
Move from soil to endodermis in apoplast Move from endodermis to xylem in symplast
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Nutrient transport in roots
Move from endodermis to xylem in symplast Transported into xylem by H+ antiporters
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Nutrient transport in roots
Move from endodermis to xylem in symplast Transported into xylem by H+ antiporters, channels
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Nutrient transport in roots
Transported into xylem by H+ antiporters, channels,pumps
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Nutrient transport in roots
Transported into xylem by H+ antiporters, channels,pumps Lowers xylem water potential -> root pressure
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Water Transport Passes water & nutrients to xylem Ys of xylem makes root pressure Causes guttation: pumping water into shoot
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Transport to shoot Nutrients move up plant in xylem sap
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Nutrient transport in leaves
Xylem sap moves through apoplast Leaf cells take up what they want
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Nutrient assimilation
Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd)
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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-
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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-
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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
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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!
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Nutrient assimilation
Most explosives are based on N or S! Most nutrient assimilation occurs in source leaves!
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N cycle Must convert N2 to a form that can be assimilated N2 -> NO3- occurs in atmosphere: lightning (8%) & Photochemistry (2%) of annual total fixed Remaining 90% comes from biological fixation to NH4+
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N cycle Soil bacteria denitrify NO3- & NH4+ back to N2 Plants must act fast! Take up NO3- & NH4+ but generally prefer NO3- Main form available due to bacteria
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N assimilation by non-N fixers
Nitrate reductase in cytoplasm reduces NO3- to NO2- NO3- + NADPH = NO2- + NADP+ large enzyme with FAD & Mo cofactors NO2- is imported to plastids & reduced to NH4+ by nitrite reductase
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N assimilation by non-N fixers
NO2- is imported to plastids & reduced to NH4+ by nitrite reductase NO Fdred + 8 H+ = NH Fdox + 2 H2O 0.2% of NO2- is released as N2O : another reason rape & corn biofuels increase global warming
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N assimilation by non-N fixers
NO2- is imported to plastids & reduced to NH4+ by nitrite reductase NO Fdred + 8 H+ = NH Fdox + 2 H2O 0.2% of NO2- is released as N2O : another reason rape & corn biofuels increase global warming Regulated at NO3- reductase; always << NO2- reductase NO2- is toxic!
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N assimilation by non-N fixers
Regulated at NO3- reductase; always << NO2- reductase NO2- is toxic! NR induced by light & nitrate
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N assimilation by non-N fixers
Regulated at NO3- reductase; always << NO2- reductase NO2- is toxic! NR induced by light & nitrate Regulated by kinase in dark, dephosphorylation in day
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NH4 assimilation GS -> GOGAT Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi
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GS -> GOGAT Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi Glutamine + a-ketoglutarate + NADH/2 Fdred <=> 2 Glutamate + NAD+/ 2 Fdox
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GS -> GOGAT Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi Glutamine + a-ketoglutarate + NADH/2 Fdred <=> 2 Glutamate + NAD+/ 2 Fdox 3. Fd GOGAT lives in source cp
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GS -> GOGAT Fd GOGAT lives in source cp NADH GOGAT lives in sinks
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GS -> GOGAT Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi Glutamine + a-ketoglutarate + NADH/2 Fdred <=> 2 Glutamate + NAD+/ 2 Fdox 3. Use glutamate to make other a.a. by transamination
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GS -> GOGAT 3. Use glutamate to make other a.a. by transamination Glutamate, aspartate & alanine can be converted to the other a.a.
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S assimilation SO42- comes from weathering or from rain: now an important source! Main thing that makes rain acid!
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S assimilation S is used in cysteine & methionine
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S assimilation S is used in cysteine & methionine Also used in CoA, S-adenosylmethionine
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S assimilation S is used in cysteine & methionine Also used in CoA, S-adenosylmethionine Also used in sulphoquinovosyl-diacylglycerol
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S assimilation S is used in cysteine & methionine Also used in CoA, S-adenosylmethionine Also used in sulphoquinovosyl-diacylglycerol And in many storage compounds: eg allicin (garlic)
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S assimilation SO42- comes from weathering or from rain: now an important source! Main thing that makes rain acid! Some bacteria use SO42- as e- acceptor -> H2S
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S assimilation SO42- comes from weathering or from rain: now an important source! Main thing that makes rain acid! Some bacteria use SO42- as e- acceptor -> H2S Some photosynthetic bacteria use reduced S as e- donor!
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S assimilation SO42- comes from weathering or from rain: now an important source! Main thing that makes rain acid! Some bacteria use SO42- as e- acceptor -> H2S Some photosynthetic bacteria use reduced S as e- donor! Now that acid rain has declined in N. Europe Brassica & wheat need S in many places
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S assimilation SO4 2- is taken up by roots & transported to leaves in xylem Most is reduced in cp
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S assimilation SO4 2- is taken up by roots & transported to leaves in xylem Most is reduced in cp 1. add SO4 2- to ATP -> APS
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S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione
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S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione S-sulfoglutathione + GSH -> SO32- + GSSG
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S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione S-sulfoglutathione + GSH -> SO32- + GSSG Sulfite + 6 Fd -> Sulfide
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S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione S-sulfoglutathione + GSH -> SO32- + GSSG Sulfite + 6 Fd -> Sulfide Sulfide + O-acetylserine -> cysteine + acetate O-acetylserine was made from serine + acetyl-CoA
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S assimilation Most cysteine is converted to glutathione or methionine
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S assimilation Most cysteine is converted to glutathione or methionine Glutathione is main form exported
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S assimilation Most cysteine is converted to glutathione or methionine Glutathione is main form exported Also used to make many other S-compounds
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S assimilation Most cysteine is converted to glutathione or methionine Glutathione is main form exported Also used to make many other S-compounds Methionine also has many uses besides protein synthesis
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S assimilation Most cysteine is converted to glutathione or methionine Cys + homoserine -> cystathione
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S assimilation Most cysteine is converted to glutathione or methionine Cys + homoserine -> cystathione Cystathione -> homocysteine + Pyruvate + NH4+
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S assimilation Most cysteine is converted to glutathione or methionine Cys + homoserine -> cystathione Cystathione -> homocysteine + Pyruvate + NH4+ Homocysteine + CH2=THF -> Met + THF 80% of met is converted to S-adenosylmethionine & used for biosyntheses
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S assimilation Most cysteine is converted to glutathione or methionine Glutathione is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine
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S assimilation Glutathione (GluCysGly) is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine g-glutamyl cysteine + glycine -> glutathionine
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S assimilation Glutathione (GluCysGly) is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine g-glutamyl cysteine + glycine -> glutathionine Glutathione is precursor for many chemicals, eg phytochelatins
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S assimilation Glutathione (GluCysGly) is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine g-glutamyl cysteine + glycine -> glutathionine Glutathione is precursor for many chemicals, eg phytochelatins SAM & glutathione are also precursors for many cell wall components
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Assignment 1 Pick a secondary compound and figure out how to measure it
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Assignment 2 Design a way to see how plants are responding to the stress
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