Plant defense responses Hypersensitive response

Plant defense responses Hypersensitive response
Prepare a 10’ talk for Friday March 3 on plant defense responses or describe interactions between plants& pathogens, pests or symbionts Plant defense responses Hypersensitive response Systemic acquired resistance Innate immunity Phytoalexin synthesis Defensins and other proteins Oxidative burst Some possible pests Nematodes Rootworms Aphids Thrips Gypsy moths hemlock woolly adelgid Some possible pathogens Agrobacterium tumefaciens Agrobacterium rhizogenes Pseudomonas syringeae Pseudomonas aeruginosa Viroids DNA viruses RNA viruses Fungi Oomycetes Some possible symbionts N-fixing bacteria N-fixing cyanobacteria Endomycorrhizae Ectomycorrhizae

Plant Respiration Recovers energy stored by photosynthesis C6H12O6 + 6 O2 <=> 6 CO2 + 6 H2O + energy Occurs in all plant tissues: even source leaves in light! Releases 50% of fixed CO2

Plant Respiration Releases 50% of fixed CO2 Provides energy for all sinks, source leaves at night & helps source during day!

Plant Respiration Provides energy for many processes embryogenesis

Plant Respiration Provides energy for many processes Embryogenesis Seed dormancy and germination Seedling morphogenesis

Plant Respiration Similar, but more complex than in animals Making precursors, recycling products, releasing energy are also important

Plant Respiration Glycolysis in cytosol Pyruvate oxidation in mito Krebs cycle in mito Electron transport & chemiosmosis in mito

Plant Respiration Glycolysis in cytosol 1 glucose -> 2 pyruvate Yields 2 NADH & 2 ATP per glucose Unique features in plants May start with DHAP from cp instead of glucose

Unique features in plants
May start with DHAP from cp instead of glucose May yield malate cf pyr PEP ->OAA by PEPC, then reduced to malate

Plant Respiration May yield malate cf pyr PEP ->OAA by PEPC, then reduced to malate Get more ATP/NADH in mito

Unique features in plants
May yield malate cf pyr PEP ->OAA by PEPC, then reduced to malate Get more ATP/NADH in mito Replaces substrates

Plant Respiration Glycolysis in cytosol 1 glucose -> 2 pyruvate Yields 2 NADH & 2 ATP per glucose Anaerobic plants ferment pyr to regenerate NAD+ Form EtOH

Plant Respiration Glycolysis in cytosol 1 glucose -> 2 pyruvate Yields 2 NADH & 2 ATP per glucose Anaerobic plants ferment pyr to regenerate NAD+ Form EtOH Less toxic than lactate because diffuses away

Plant Respiration Krebs cycle Similar, but more complex Key role is making intermediates & recycling products

Plant Respiration Krebs cycle Similar, but more complex Key role is making intermediates & recycling products Many ways to feed in other substrates to burn

Plant Respiration Krebs cycle Similar, but more complex Key role is making intermediates & recycling products Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis

Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going

Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going Malic enzyme is key: lets cell burn malate or citrate from other sources

Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going Malic enzyme is key: lets cell burn malate or citrate from other sources PEPCarboxylase lets cell replace Krebs intermediates used for synthesis

Plant Respiration Pentose phosphate shunt in cytosol or cp 6 glucose-6P + 12NADP++ 7 H2O -> 5 glucose-6P + 6 CO NADPH +12 H+ : makes NADPH & intermediates

Plant Respiration Pentose phosphate shunt in cytosol or cp makes NADPH & intermediates Uses many Calvin Cycle enzymes

Plant Respiration Pentose phosphate shunt in cytosol or cp makes NADPH & intermediates Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors

Plant Respiration Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors Gets Calvin cycle started at dawn

ATP generation 2 stages 1) e- transport 2) chemiosmotic ATP synthesis

Three steps transport H+ across membrane
1) NADH dehydrogenase pumps 4 H+/ 2 e- 2) Cyt bc1 pumps 4 H+/ 2 e- 3) Cyt c oxidase pumps 2 H+/ 2 e- and adds 2 H+ to O to form H2O

e- transport Plants have additional enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+

e- transport Plants have additional enzymes! NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone

Additional e- transport enzymes!
NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone Helps burn off excess NADH from making precursors

NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone Helps burn off excess NADH from making precursors Much lower affinity for NADH than complex I

NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone Helps burn off excess NADH from making precursors Much lower affinity for NADH than complex I Energy is released as heat

NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone Helps burn off excess NADH from making precursors Energy is released as heat NADH dehydrogenase in intermembrane space that transfers e- from NADH to UQ w/o pumping H+

NADH dehydrogenase in intermembrane space that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone "imports" e- from cytoplasmic NADH Much lower affinity for NADH than complex I Energy is released as heat

Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+

Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ Insensitive to Cyanide, Azide or CO

Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ Insensitive to Cyanide, Azide or CO Sensitive to SHAM (salicylhydroxamic acid)

Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ Insensitive to Cyanide, Azide or CO Sensitive to SHAM (salicylhydroxamic acid) Also found in fungi, trypanosomes & Plasmodium

Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ Also found in fungi, trypanosomes & Plasmodium Energy lost as heat: can raise Voodoo lilies 25˚ C

Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ Plants also have an uncoupler protein: lets H+ in w/o doing work!

Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ Plants also have an uncoupler protein: lets H+ in w/o doing work! Why so many ways to reduce ATP synthesis efficiency?

Why so many ways to reduce ATP synthesis efficiency? Regenerate NAD+ needed for precursor synthesis

Why so many ways to reduce ATP synthesis efficiency? Regenerate NAD+ needed for precursor synthesis Generate heat

Why so many ways to reduce ATP synthesis efficiency? Regenerate NAD+ needed for precursor synthesis Generate heat Burn off excess energy captured by photosynthesis

Additional e- transport enzymes! Additional e- transport enzymes!
Why so many ways to reduce ATP synthesis efficiency? Regenerate NAD+ needed for precursor synthesis Generate heat Burn off excess energy captured by photosynthesis Prevalence says they're doing something important! Additional e- transport enzymes! Why so many ways to reduce ATP synthesis efficiency? Regenerate NAD+ needed for precursor synthesis Generate heat Burn off excess energy captured by photosynthesis Prevalence says they're doing something important!

Import/export from mitochondria
I) Exchanging ATP for ADP uses antiport driven by ∆E ATP4- is traded for ADP3- Lose one + charge

II) Pi is imported by an OH- antiporter exchanging ATP for ADP + Pi uses 1 H+ and one + charge

II) Pi is imported by an OH- antiporter exchanging ATP for ADP + Pi uses 1 H+ and one + charge Use ∆Pi for other import

II) Pi is imported by an OH- antiporter III) Pyruvate is imported by an OH- antiporter

II) Pi is imported by an OH- antiporter III) Pyruvate is imported by an OH- antiporter IV) Malate is imported by PI antiporter

II) Pi is imported by an OH- antiporter III) Pyruvate is imported by an OH- antiporter IV) Malate is imported by PI antiporter or by faciitated diffusion

II) Pi is imported by an OH- antiporter III) Pyruvate is imported by an OH- antiporter IV) Malate is imported by PI antiporter or by facilitated diffusion V) Other TCA intermeds exchanged by facilitated diffusion

VI) Mito DNA encodes ~ 35 proteins, also rRNA & tRNA subunits of ATP synthase & complexes I, II, III & IV

VI) Mito DNA encodes ~ 35 proteins, also rRNA & tRNA subunits of ATP synthase & complexes I, II, III & IV some mRNA are trans-spliced from 2 diff transcripts!

VI) Mito DNA encodes ~ 35 proteins, also rRNA & tRNA subunits of ATP synthase & complexes I, II, III & IV some mRNA are trans-spliced from 2 diff transcripts! some mRNA are edited: bases changed after synthesis!

VI) Mito DNA encodes ~ 35 proteins, also rRNA & tRNA subunits of ATP synthase & complexes I, II, III & IV some mRNA are trans-spliced from 2 diff transcripts! some mRNA are edited: bases changed after synthesis! mtDNA recombines to form new genes, some poison pollen development to create cytoplasmic male sterility

VI) Mito DNA encodes ~ 35 proteins, also rRNA & tRNA subunits of ATP synthase & complexes I, II, III & IV some mRNA are trans-spliced from 2 diff transcripts! some mRNA are edited: bases changed after synthesis! mtDNA recombines to form new genes, some poison pollen development to create cytoplasmic male sterility Pollen don't transmit mito!

VI) Mito DNA encodes ~ 35 proteins, also rRNA & tRNA subunits of ATP synthase & complexes I, II, III & IV some mRNA are trans-spliced from 2 diff transcripts! some mRNA are edited: bases changed after synthesis! mtDNA recombines to form new genes, some poison pollen development to create cytoplasmic male sterility Pollen don't transmit mito! Other 2000 proteins are imported from cytosol post-translationally made with N-terminal presequence targeting them to mito

VI) Mito genome encodes ~ 35 proteins, remainder are imported from cytosol post-translationally made with N-terminal presequence targeting them to mito

Protein import into mitochondria
1) HSP70 binds & unfolds preprotein

1) HSP70 binds & unfolds preprotein 2) Unfolded presequence binds MOM receptors

1) HSP70 binds & unfolds preprotein 2) Unfolded presequence binds MOM receptors 3) Unfolded protein is translocated through MOM controversy: do inner and outer membrane contact each other before protein import?

1) HSP70 binds & unfolds preprotein 2) Unfolded presequence binds MOM receptors 3) Unfolded protein is translocated through MOM 4) Unfolded protein is translocated through MIM

1) HSP70 binds & unfolds preprotein 2) Unfolded presequence binds MOM receptors 3) Unfolded protein is translocated through MOM 4) Unfolded protein is translocated through MIM 5) Chaperones in matrix refold protein

1) HSP70 binds & unfolds preprotein 2) Unfolded presequence binds MOM receptors 3) Unfolded protein is translocated through MOM 4) Unfolded protein is translocated through MIM 5) Chaperones in matrix refold protein 6) Clip presequence

Driving forces for import:
1)∆E (on +ve a.a.) 2) Refolding (Brownian ratchet) 3) ATP hydrolysis used to drive unfolding and refolding

Regulating Respiration
Regulated by demand for ATP, NADPH and substrates

Glycolysis is allosterically regulated at 3 irreversible steps
Hexokinase is allosterically inhibited by its product: G-6P Allosteric site has lower affinity than active site

Glycolysis is allosterically regulated at 3 irreversible steps
Hexokinase is allosterically inhibited by its product: G-6P Pyr kinase is allosterically inhibited by ATP & citrate

Regulating Glycolysis
Main regulatory step is Phosphofructokinase Rate-limiting step Committed step

Regulating Glycolysis
Main regulatory step is Phosphofructokinase Inhibited by Citrate, PEP & ATP Stimulated by ADP

Regulating Pyruvate DH
Mainly by a kinase Inhibited when Pi added

Mainly by a kinase Inhibited when Pi added NADH, Acetyl CoA, ATP NH4+ inhibit PDH & activate kinase

Mainly by a kinase Inhibited when Pi added NADH, Acetyl CoA, ATP NH4+ inhibit PDH & activate kinase Activated when no Pi ADP, pyruvate inhibit kinase

REGULATING THE KREBS CYCLE
Krebs cycle is allosterically regulated at 4 enzymes citrate synthase Isocitrate dehydrogenase 3) a-ketoglutarate dehydrogenase 4) Malate dehydrogenase

REGULATING THE KREBS CYCLE
Krebs cycle is allosterically regulated at 4 enzymes citrate synthase Isocitrate dehydrogenase 3) a-ketoglutarate dehydrogenase 4) Malate dehydrogenase All are inhibited by NADH & products

Environmental factors
Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature

Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO2 Respiration declines if pO2 <5%

Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO2 Respiration declines if pO2 <5% Problem for flooded roots

Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO2 Respiration declines if pO2 <5% Problem for flooded roots pCO2 Inhibits respiration at 3%

Temperature Rate ~ doubles for each 10˚ C increase up to ~ 40˚ At higher T start to denature 2) pO2 Respiration declines if pO2 <5% Problem for flooded roots pCO2 Inhibits respiration at 3% No obvious effects at 700 ppm, yet biomass reduced

Plant defense responses Hypersensitive response

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Plant defense responses Hypersensitive response

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