Transcript Bio 226: Cell and Molecular Biology

Pathogens
• Agrobacterium tumefaciens: Greg
• Agrobacterium rhizogenes
• Pseudomonas syringeae
• Pseudomonas aeruginosa: Mike
• Viroids: Bryant
• DNA viruses
• RNA viruses: Rob
• Fungi : Connor
• oomycetes
• Nematodes: Chris
Symbionts
• N-fixers
• Endomycorrhizae
• Ectomycorrhizae
Nutrient transport in roots
Move from soil to endodermis in apoplast
Move from endodermis to xylem in symplast
Nutrient transport in roots
Transported into xylem by H+ antiporters, channels,pumps
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!
Nutrient assimilation
Most explosives are based on N or S!
Most nutrient assimilation occurs in source leaves!
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+
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
N assimilation by non-N fixers
Nitrate reductase in cytoplasm reduces
NO3- to NO2NO3- + NADPH = NO2- + NADP+
large enzyme with FAD & Mo cofactors
NO2- is imported to plastids & reduced
to NH4+ by nitrite reductase
N assimilation by non-N fixers
NO2- is imported to plastids & reduced
to NH4+ by nitrite reductase
NO2- + 6 Fdred + 8 H+ = NH4+ + 6 Fdox + 2 H2O
N assimilation by non-N fixers
NO2- is imported to plastids & reduced
to NH4+ by nitrite reductase
NO2- + 6 Fdred + 8 H+ = NH4+ + 6 Fdox + 2 H2O
Regulated at NO3- reductase; always << NO2- reductase
NO2- is toxic!
N assimilation by non-N fixers
Regulated at NO3- reductase; always << NO2- reductase
NO2- is toxic!
NR induced by light & nitrate
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
NH4 assimilation
GS -> GOGAT
1. Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi
GS -> GOGAT
1. Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi
2. Glutamine + a-ketoglutarate + NADH/2 Fdred <=>
2 Glutamate + NAD+/ 2 Fdox
GS -> GOGAT
1. Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi
2. Glutamine + a-ketoglutarate + NADH/2 Fdred <=>
2 Glutamate + NAD+/ 2 Fdox
3. Fd GOGAT lives in source cp
GS -> GOGAT
Fd GOGAT lives in source cp
• NADH GOGAT lives in sinks
GS -> GOGAT
1. Glutamate + NH4+ + ATP <=> Glutamine + ADP +Pi
2. Glutamine + a-ketoglutarate + NADH/2 Fdred <=>
2 Glutamate + NAD+/ 2 Fdox
3. Use glutamate to make other a.a. by transamination
GS -> GOGAT
3. Use glutamate to make other a.a. by transamination
Glutamate, aspartate & alanine can be converted to the
other a.a.
S assimilation
SO42- comes from weathering or from rain: now an
important source! Main thing that makes rain acid!
S assimilation
S is used in cysteine & methionine
S assimilation
S is used in cysteine & methionine
Also used in CoA, S-adenosylmethionine
S assimilation
S is used in cysteine & methionine
Also used in CoA, S-adenosylmethionine
Also used in sulphoquinovosyl-diacylglycerol
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)
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
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!
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
S assimilation
SO4 2- is taken up by roots &
transported to leaves in xylem
Most is reduced in cp
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
S assimilation
1. add SO4 2- to ATP -> APS
2. Transfer S to Glutathione -> S-sulfoglutathione
S assimilation
1. add SO4 2- to ATP -> APS
2. Transfer S to Glutathione -> S-sulfoglutathione
3. S-sulfoglutathione + GSH -> SO32- + GSSG
1.
2.
3.
4.
S assimilation
add SO4 2- to ATP -> APS
Transfer S to Glutathione -> S-sulfoglutathione
S-sulfoglutathione + GSH -> SO32- + GSSG
Sulfite + 6 Fd -> Sulfide
1.
2.
3.
4.
5.
•
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
S assimilation
Most cysteine is converted to
glutathione or methionine
S assimilation
Most cysteine is converted to
glutathione or methionine
Glutathione is main form
exported
S assimilation
Most cysteine is converted to
glutathione or methionine
Glutathione is main form
exported
Also used to make many other
S-compounds
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
S assimilation
Most cysteine is converted to glutathione or methionine
1. Cys + homoserine -> cystathione
S assimilation
Most cysteine is converted to glutathione or methionine
1. Cys + homoserine -> cystathione
2. Cystathione -> homocysteine + Pyruvate + NH4+
S assimilation
Most cysteine is converted to glutathione or methionine
1. Cys + homoserine -> cystathione
2. Cystathione -> homocysteine + Pyruvate + NH4+
3. Homocysteine + CH2=THF -> Met + THF
4. 80% of met is converted to S-adenosylmethionine &
used for biosyntheses
S assimilation
Most cysteine is converted to glutathione or methionine
Glutathione is made enzymatically!
1. Glutamate + Cysteine -> g-glutamyl cysteine
S assimilation
Glutathione (GluCysGly) is made enzymatically!
1. Glutamate + Cysteine -> g-glutamyl cysteine
2. g-glutamyl cysteine + glycine -> glutathionine
S assimilation
Glutathione (GluCysGly) is made enzymatically!
1. Glutamate + Cysteine -> g-glutamyl cysteine
2. g-glutamyl cysteine + glycine -> glutathionine
Glutathione is precursor for many chemicals, eg
phytochelatins
S assimilation
Glutathione (GluCysGly) is made enzymatically!
1. Glutamate + Cysteine -> g-glutamyl cysteine
2. g-glutamyl cysteine + glycine -> glutathionine
Glutathione is precursor for many chemicals, eg
phytochelatins
SAM & glutathione are also precursors for many cell wall
components
Plant Growth
Size & shape depends on cell # & cell size
Plant Growth
Size & shape depends on cell # & cell size
Decide when,where and which way to divide
Plant Growth
Size & shape depends on cell # & cell size
Decide which way to divide & which way to elongate
• Periclinal = perpendicular to surface
Plant Growth
Size & shape depends on cell # & cell size
Decide which way to divide & which way to elongate
• Periclinal = perpendicular to surface: get longer
Plant Growth
Size & shape depends on cell # & cell size
Decide which way to divide & which way to elongate
• Periclinal = perpendicular to surface: get longer
• Anticlinal = parallel to surface
Plant Growth
Size & shape depends on cell # & cell size
Decide which way to divide & which way to elongate
• Periclinal = perpendicular to surface: get longer
• Anticlinal = parallel to surface: add more layers
Plant Growth
Decide which way to divide & which way to elongate
• Periclinal = perpendicular to surface: get longer
• Anticlinal = parallel to surface: add more layers
Now must decide which way to elongate
Plant Growth
Decide which way to divide & which way to elongate
• Periclinal = perpendicular to surface: get longer
• Anticlinal = parallel to surface: add more layers
Now must decide which way to elongate: which walls to
stretch
Plant Cell Walls and Growth
Carbohydrate barrier
surrounding cell
• Protects & gives cell shape
Plant Cell Walls and Growth
Carbohydrate barrier
surrounding cell
• Protects & gives cell shape
• 1˚ wall made first
• mainly cellulose
• Can stretch!
Plant Cell Walls and Growth
Carbohydrate barrier
surrounding cell
• Protects & gives cell shape
• 1˚ wall made first
• mainly cellulose
• Can stretch!
• 2˚ wall made after growth
stops
• Lignins make it tough
Plant Cell Walls and Growth
• 1˚ wall made first
• mainly cellulose
• Can stretch! Control elongation by controlling
orientation of cell wall fibers as wall is made
Plant Cell Walls and Growth
• 1˚ wall made first
• mainly cellulose
• Can stretch! Control elongation by controlling
orientation of cell wall fibers as wall is made
• 1˚ walls = 25% cellulose, 25% hemicellulose, 35%
pectin, 5% protein (but highly variable)
Plant Cell Walls and Growth
1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin,
5% protein (but highly variable)
Cellulose: ordered chains made of glucose linked b 1-4
Plant Cell Walls and Growth
1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin,
5% protein (but highly variable)
Cellulose: ordered chains made of glucose linked b 1-4
• Cross-link with neighbors to form strong, stable fibers
Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4
• Cross-link with neighbors to form strong, stable fibers
• Made by enzyme embedded in the plasma membrane
Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4
• Cross-link with neighbors to form strong, stable fibers
• Made by enzyme embedded in the plasma membrane
• Guided by cytoskeleton
Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4
• Cross-link with neighbors to form strong, stable fibers
• Made by enzyme embedded in the plasma membrane
• Guided by cytoskeleton
• Cells with poisoned
µtubules are misshapen
Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4
• Cross-link with neighbors to form strong, stable fibers
• Made by enzyme embedded in the plasma membrane
• Guided by cytoskeleton
• Cells with poisoned µtubules are misshapen
• Other wall chemicals are made in Golgi & secreted
Plant Cell Walls and Growth
Cellulose: ordered chains made of glucose linked b 1-4
• Cross-link with neighbors to form strong, stable fibers
• Made by enzyme embedded in the plasma membrane
• Guided by cytoskeleton
• Cells with poisoned µtubules are misshapen
• Other wall chemicals are made in Golgi & secreted
• Only cellulose pattern
is tightly controlled
Plant Cell Walls and Growth
Cellulose pattern is tightly controlled
• 6 CES enzymes form a “rosette”: each makes 6 chains
-> 36/fiber
Plant Cell Walls and Growth
Cellulose pattern is tightly controlled
• 6 CES enzymes form a “rosette”: each makes 6 chains
-> 36/fiber
• Rosettes are guided
by microtubules
Plant Cell Walls and Growth
Cellulose pattern is tightly controlled
• 6 CES enzymes form a “rosette”: each makes 6 chains
• Rosettes are guided by microtubules
• Deposition pattern determines direction of elongation
Plant Cell Walls and Growth
Cellulose pattern is tightly controlled
• Deposition pattern determines direction of elongation
• New fibers are perpendicular to growth direction, yet
fibers form a mesh
Plant Cell Walls and Growth
New fibers are perpendicular to growth direction, yet
fibers form a mesh
Multinet hypothesis: fibers reorient as cell elongates
Old fibers are anchored so gradually shift as cell grows
Plant Cell Walls and Growth
New fibers are perpendicular to growth direction, yet
fibers form a mesh
Multinet hypothesis: fibers reorient as cell elongates
Old fibers are anchored so gradually shift as cell grows
Result = mesh