Pathogens • Agrobacterium tumefaciens • Agrobacterium rhizogenes • Pseudomonas syringeae • Pseudomonas aeruginosa • Viroids • DNA viruses • RNA viruses • Fungi • oomycetes • nematodes Symbionts • N-fixers • Endomycorrhizae • Ectomycorrhizae
Jan 01, 2016
Pathogens• Agrobacterium tumefaciens • Agrobacterium rhizogenes• Pseudomonas syringeae• Pseudomonas aeruginosa• Viroids• DNA viruses• RNA viruses• Fungi• oomycetes• nematodes
Symbionts• N-fixers• Endomycorrhizae• Ectomycorrhizae
Plant GrowthDecide which way to divide & which way to elongate• Periclinal = perpendicular to surface: get longer• Anticlinal = parallel to surface: add more layersNow must decide which way to elongate: which walls to
stretch
Plant Cell Walls and GrowthCarbohydrate barriersurrounding 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•1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable)
Plant Cell Walls and Growth1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin,
5% protein (but highly variable)Cellulose: ordered chains made of glucose linked1-4• Cross-link with neighbors to form strong, stable fibers
Plant Cell Walls and GrowthCellulose: ordered chains made of glucose linked 1-4• Cross-link with neighbors to form strong, stable fibers• Made by enzyme embedded in the plasma membrane
Plant Cell Walls and GrowthCellulose: ordered chains made of glucose linked 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 GrowthCellulose: ordered chains made of glucose linked 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 GrowthCellulose: ordered chains made of glucose linked 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 GrowthCellulose: ordered chains made of glucose linked 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 GrowthCellulose pattern is tightly controlled• 6 CES enzymes form a “rosette”: each makes 6 chains
-> 36/fiber
Plant Cell Walls and GrowthCellulose 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 GrowthCellulose 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 GrowthCellulose 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 GrowthNew fibers are perpendicular to growth direction, yet
fibers form a meshMultinet hypothesis: fibers reorient as cell elongatesOld fibers are anchored so gradually shift as cell grows
Plant Cell Walls and GrowthNew fibers are perpendicular to growth direction, yet
fibers form a meshMultinet hypothesis: fibers reorient as cell elongatesOld fibers are anchored so gradually shift as cell growsResult = mesh
Plant Cell Walls and Growth1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin,
5% protein (but highly variable)Hemicelluloses AKA cross-linking glycans: bind cellulose
Plant Cell Walls and GrowthHemicelluloses AKA cross-linking glycans: bind celluloseCoat cellulose & bindneighbor
Plant Cell Walls and GrowthHemicelluloses AKA cross-linking glycansCoat cellulose & bind neighborDiverse group of glucans: also linked 1-4, but may have
other sugars and components attached to C6
HemicellulosesDiverse group of glucans: also linked 1-4, but may have
other sugars and components attached to C6 makes digestion more difficult
HemicellulosesDiverse group of glucans: also linked 1-4, but may have
other sugars and components attached to C6 makes digestion more difficultAssembled in Golgi
Plant Cell Walls and GrowthHemicelluloses AKA cross-linking glycansA diverse group of glucans also linked 1-4, but may
have other sugars and components attached to C6makes digestion more difficultAssembled in GolgiSecreted cf woven
Plant Cell Walls and Growth1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin,
5% protein (but highly variable)Pectins: fill space between cellulose-hemicellulose fibers
PectinsPectins: fill space between cellulose-hemicellulose fibersForm gel that determines cell wall porosity(& makes jam)
PectinsPectins: fill space between cellulose-hemicellulose fibersForm gel that determines cell wall porosity (& makes jam)Acidic, so also modulate pH & bind polars
PectinsPectins: fill space between cellulose-hemicellulose fibersForm gel that determines cell wall porosity (& makes jam)Acidic, so also modulate pH & bind polarsBackbone is 1-4 linked galacturonic acid
Plant Cell Walls and GrowthAlso 4 main multigenic families of structural proteinsAmounts vary between cell types & conditions
Plant Cell Walls and GrowthAlso 4 main multigenic families of structural proteinsAmounts vary between cell types & conditions1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)• Proline changed to hydroxyproline in Golgi
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)• Proline changed to hydroxyproline in Golgi• Highly glycosylated: helps bind CH2O
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)• Proline changed to hydroxyproline in Golgi• Highly glycosylated: helps bind CH2O• Common in cambium, phloem
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)• Proline changed to hydroxyproline in Golgi• Highly glycosylated: helps bind CH2O• Common in cambium, phloem• Help lock the wall after growth ceases
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)• Proline changed to hydroxyproline in Golgi• Highly glycosylated: helps bind CH2O• Common in cambium, phloem• Help lock the wall after growth ceases• Induced by wounding2. PRP: proline-rich proteins
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins• Low glycosylation = little interaction with CH2O
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins• Low glycosylation = little interaction with CH2O• Common in xylem, fibers, cortex
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins• Low glycosylation = little interaction with CH2O• Common in xylem, fibers, cortex• May help lock HRGPs together
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins• Low glycosylation = little interaction with CH2O• Common in xylem, fibers, cortex• May help lock HRGPs together3. GRP: Glycine-rich proteins• No glycosylation = little interaction with CH2O
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins• Low glycosylation = little interaction with CH2O• Common in xylem, fibers, cortex• May help lock HRGPs together3. GRP: Glycine-rich proteins• No glycosylation = little interaction with CH2O• Common in xylem
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins• Low glycosylation = little interaction with CH2O• Common in xylem, fibers, cortex• May help lock HRGPs together3. GRP: Glycine-rich proteins• No glycosylation = little interaction with CH2O• Common in xylem• May help lock HRGPs & PRPs together
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins3. GRP: Glycine-rich proteins• No glycosylation = little interaction with CH2O• Common in xylem• May help lock HRGPs & PRPs together4. Arabinogalactan proteins
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins3. GRP: Glycine-rich proteins4. Arabinogalactan proteins• Highly glycosylated: helps bind CH2O
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins3. GRP: Glycine-rich proteins4. Arabinogalactan proteins• Highly glycosylated: helps bind CH2O• Anchored to PM by GPI
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins3. GRP: Glycine-rich proteins4. Arabinogalactan proteins• Highly glycosylated: helps bind CH2O• Anchored to PM by GPI• Help cell adhesion and cell signaling
Plant Cell Wall Proteins1. HRGP: hydroxyproline-rich glycoproteins (eg extensin)2. PRP: proline-rich proteins3. GRP: Glycine-rich proteins4. Arabinogalactan proteins• Highly glycosylated: helps bind CH2O• Anchored to PM by GPI• Help cell adhesion and cell signaling5. Also many enzymes involved in cell wall synthesis and
loosening
Plant Cell Walls and GrowthAlso many enzymes involved in cell wall synthesis and
looseningAs growth stops, start making lignins & linking HGRP
Plant Cell Walls and GrowthAs growth stops, start depositing lignins & linking HGRPLignins = polyphenolic macromolecules: 2nd most
abundant on earth (after cellulose)
Plant Cell Walls and GrowthLignins = polyphenolic macromolecules: 2nd most
abundant on earth (after cellulose)Bond hemicellulose: solidify & protect cell wall (nature’s
cement): very difficult to digest
Plant Cell Walls and GrowthLignins = polyphenolic macromolecules: 2nd most
abundant on earth (after cellulose)Bond hemicellulose: solidify & protect cell wall (nature’s
cement): very difficult to digestMonomers are made in cytoplasm & secreted
Plant Cell Walls and GrowthMonomers are made in cytoplasm & secretedPeroxidase & laccase in cell wall create radicals that
polymerise non-enzymatically
Plant Cell Walls and GrowthMonomers are made in cytoplasm & secretedPeroxidase & laccase in cell wall create radicals that
polymerise non-enzymatically
Plant Cell Walls and GrowthPeroxidase & laccase in cell wall create radicals that
polymerise non-enzymaticallyVery difficult to digest, yet major plant component!
Plant Cell Walls and GrowthAs growth stops, start depositing lignins & linking HGRPSolidify & protect cell wall: very difficult to digestElongation precedes lignification
Plant Cell Walls and GrowthAs growth stops, start depositing lignins & linking HGRPSolidify & protect cell wall: very difficult to digestElongation precedes lignificationRequires loosening the bonds joining the cell wall
Plant Cell Walls and GrowthElongation precedes lignificationRequires loosening the bonds joining the cell wallCan’t loosen too much or cell will burst
Plant Cell Walls and GrowthElongation precedes lignificationRequires loosening the bonds joining the cell wallCan’t loosen too much or cell will burstMust coordinate with cell wall synthesis so wall stays same
Plant Cell Walls and GrowthElongation: loosening the bonds joining the cell wallCan’t loosen too much or cell will burstMust coordinate with cell wall synthesis so wall stays sameMust weaken crosslinks joining cellulose fibers
Plant Cell Walls and GrowthMust weaken crosslinks joining cellulose fibersTurgor pressure then makes cells expand
Plant Cell Walls and GrowthMust weaken crosslinks joining cellulose fibersTurgor pressure then makes cells expand• Lower pH: many studies show that lower pH is
sufficient for cell elongation
Plant Cell Walls and GrowthMust weaken crosslinks joining cellulose fibers• Lower pH: many studies show that lower pH is
sufficient for cell elongationAcid growth hypothesis: Growth regulators cause
elongation by activating H+ pump
Plant Cell Walls and GrowthAcid growth hypothesis: Growth regulators cause
elongation by activating H+ pump• Inhibitors of H+ pump stop elongation• But: Cosgrove isolated proteins that loosen cell wall• Test protein extracts
to see if wall loosens
Plant Cell Walls and GrowthAcid growth hypothesis: Growth regulators cause
elongation by activating H+ pump• But: Cosgrove isolated proteins that loosen cell wall• Test protein extracts to see if wall loosens• Identified expansin proteins that enhance acid growth
Plant Cell Walls and GrowthAcid growth hypothesis: Growth regulators cause
elongation by activating H+ pump• But: Cosgrove isolated proteins that loosen cell wall• Test protein extracts to see if wall loosens• Identified expansin proteins that enhance acid growth• Still don’t know how they work!
Plant Cell Walls and Growth• Identified expansin proteins that enhance acid growth• Still don’t know how they work! • Best bet, loosen Hemicellulose/cellulose bonds
Plant Cell Walls and GrowthAlso have endoglucanases and transglucanases that cut &
reorganize hemicellulose & pectin
Plant Cell Walls and GrowthAlso have endoglucanases and transglucanases that cut &
reorganize hemicellulose & pectin XET (xyloglucan endotransglucosylase) is best-known
Plant Cell Walls and GrowthAlso have endoglucanases and transglucanases that cut &
reorganize hemicellulose & pectin XET (xyloglucan endotransglucosylase) is best-knownCuts & rejoins hemicellulose in new ways
Plant Cell Walls and GrowthXET is best-knownCuts & rejoins hemicellulose in new waysExpansins & XET catalyse cell wall creepage
Plant Cell Walls and GrowthXET is best-knownCuts & rejoins hemicellulose in new waysExpansins & XET catalyse cell wall creepageUpdated acid growth hypothesis: main function of
lowering pH is activating expansins and glucanases
Plant Cell Walls and GrowthUpdated acid growth hypothesis: main function of
lowering pH is activating expansins and glucanasesCoordinated with synthesis of new cell wall to keep
thickness constant
Plant Cell Walls and SignalingPathogens must digest cell wall to enter plantRelease cell wall fragments
Plant Cell Walls and SignalingPathogens must digest cell wall to enter plantRelease cell wall fragmentsMany oligosaccharides signal”HELP!”
Plant Cell Walls and SignalingPathogens must digest cell wall to enter plantRelease cell wall fragmentsMany oligosaccharides signal”HELP!”Elicit plant defense responses
Growth regulators1.Auxins2.Cytokinins3.Gibberellins4.Abscisic acid5.Ethylene6.BrassinosteroidsAll are small organics: made inone part, affectanother part
Growth regulatorsAll are small organics: made in one part, affect another partTreating a plant tissue with a hormone is like putting a dime in a vending machine. It depends on the machine, not the dime!
AuxinFirst studied by Darwins!Showed that a "transmissible influence" made at tips caused bending lower down
AuxinFirst studied by Darwins!Showed that a "transmissible influence" made at tips caused bending lower downNo tip, no curve!
AuxinFirst studied by Darwins!Showed that a "transmissible influence" made at tips caused bending lower downNo tip, no curve!1913:Boysen-Jensen showed that diffused through agar blocks but not through mica
Auxin1913:Boysen-Jensen showed that diffused through agar blocks but not through mica1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark
Auxin1913:Boysen-Jensen showed that diffused through agar blocks but not through mica1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in darkUneven amounts of "transmissible influence" makes bend
Auxin1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in darkUneven amounts of "transmissible influence" makes bend1926: Went showed that a chemical that diffused from tips into blocks caused growth
Auxin1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in darkUneven amounts of "transmissible influence" makes bend1926: Went showed that a chemical that diffused from tips into blocks caused growthIf placed asymmetrically get bending due to asymmetrical growth
Auxin1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in darkUneven amounts of "transmissible influence" makes bend1926: Went showed that a chemical that diffused from tips into blocks caused growthIf placed asymmetrically get bending due to asymmetrical growthAmount of bending depends on [auxin]
Auxin1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in darkUneven amounts of "transmissible influence" makes bend1926: Went showed that a chemical that diffused from tips into blocks caused growthIf placed asymmetrically get bending due to asymmetrical growthAmount of bending depends on [auxin]1934: Indole-3-Acetic acid (IAA) from the urine of pregnant women was shown to cause bending
Auxin1934: Indole-3-Acetic acid (IAA) from the urine of pregnant women was shown to cause bendingIAA is the main auxin in vivo.Others include Indole-3-butyric acid (IBA), 4-Chloroindole-3-acetic acid and phenylacetic acid (PA)
IBAIBA
PAPA4-CI-IAA
IAAIAA
AuxinIAA is the main auxin in vivo.Many synthetic auxins have been identifiedNo obvious structural similarity, yet all work!
IAAIAA
AuxinIAA is the main auxin in vivo.Many synthetic auxins have been identifiedNo obvious structural similarity, yet all work!Widely used in agriculture
IAAIAA
AuxinIAA is the main auxin in vivo.Many synthetic auxins have been identifiedNo obvious structural similarity, yet all work!Widely used in agriculture • to promote growth (flowering, cuttings)
IAAIAA