Transcript Feb 3
Plan C We will pick a problem in plant biology and see where it takes us. 1. Plant products 2. Climate/CO2 change 3. Stress responses/stress avoidance Plants & products chosen 1. Capsaicin Capsicum sp. 1. Glucosinolates Radishes (Raphanus sativus) Mustard (Brassica juncea) 2. Alliin -> Allicin Garlic (Allium sativum) Other candidates 1. Propanethial-S-oxide Onions (Allium cepa) 1. Portulacanones Purslane (Portulaca oleracea) 2. Allyl isothiocyanate Horseradish (Armoracia rusticana) Wasabi (Eutrema japonicum) 1. eugenol (and others) Basil (Ocimum basilicum) Stresses Chosen 1. Climate change • Temperature • Increased pCO2 • Drought 2. pH 3. Nutrient deprivation 4. Metal toxicity (a result of low pH) 5. Predation 6. Shaking Next Friday Present a plant stressor, what is known about it, and why it might affect plant 2˚ compounds in an ~ 10 minute presentation. Alternative: present another good plant/stressor response to study and why we should choose it over the ones already chosen. Nutrient transport in roots Move from soil to endodermis in apoplast Move from endodermis to xylem in symplast Nutrient uptake Taken into endodermis by H+ symporters, channels, pumps Nutrient transport in roots Move from endodermis to xylem in symplast 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) • 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 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 0.2% of NO2- is released as N2O : another reason rape & corn biofuels increase global warming 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 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! 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. 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 e-transfer sites N assimilation by N fixers O2 binds & inactivates e-transfer sites Heterocysts lack PSII, have other mechs to lower pO2 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 coiling • 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 coiling • 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! S assimilation SO42- comes from weathering or from rain: now an important source! Main cause of 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 chems, 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 Secondary Metabolites 1˚ metabolites are essential for growth & development •therefore present in all plants 2˚ metabolites “not” required for growth & development •therefore not present in all plants Natural Products 1˚ metabolites are essential for growth & development •therefore present in all plants 2˚ metabolites “not” required for growth & development •therefore not present in all plants •Often only found in one or a few spp. capsaicin Nepetalactone Menthol Natural Products 1˚ metabolites are essential for growth & development •therefore present in all plants 2˚ metabolites “not” required for growth & development •therefore not present in all plants •Often only found in one or a few spp. Derived from 1˚ metabs Natural Products 2˚ metabolites “not” required for growth & development •therefore not present in all plants •Often only found in one or a few spp. Derived from 1˚ metabs, can be hard to draw line Natural Products 2˚ metabolites “not” required for growth & development •therefore not present in all plants •Often only found in one or a few spp. Derived from 1˚ metabs, can be hard to draw line Natural Products 2˚ metabolites not present in all plants •Often only found in one or a few spp. •Derived from 1˚ metabs, can be hard to draw line •Can be up to 3% of dry weight: very expensive to the the plant! Natural Products >100,000 types; tremendous variety of functions 1. Defense • Herbivores Natural Products >100,000 types; tremendous variety of functions 1. Defense • Herbivores • Pathogens Resveratrol Natural Products >100,000 types; tremendous variety of functions 1. Defense • Herbivores • Pathogens • Other plants leptospermone Natural Products >100,000 types; tremendous variety of functions 1. Defense 2. Attractant • Pollinators • Odors • Colors Natural Products >100,000 types; tremendous variety of functions 1. Defense 2. Attractant • Pollinators • Symbionts Natural Products >100,000 types; tremendous variety of functions 1. Defense 2. Attractant • Pollinators • Symbionts • Seed dispersers Methyl anthranilate(strawberries) Pentyl butyrate (pears, apricots) Natural Products >100,000 types; tremendous variety of functions 1.Defense 2.Attractant • Pollinators • Symbionts • Seed dispersers • “protectors” (tritrophic interactions) Natural Products >100,000 types; tremendous variety of functions 1. Defense 2. Attractant 3. Protecting from UV Natural Products >100,000 types; tremendous variety of functions 1. Defense 2. Attractant 3. Protecting from UV 4. metal uptake and transport Natural Products >100,000 types; tremendous variety of functions 1. Defense 2. Attractant 3. Protecting from UV 4. metal uptake and transport 5. Hardening cell walls Natural Products >100,000 types; tremendous variety of functions Some are made constitutively Natural Products >100,000 types; tremendous variety of functions Some are made constitutively Others are induced, especially defense compounds Natural Products >100,000 types; tremendous variety of functions Some are made constitutively, others are induced Made in many cellular locations • Cytoplasm: most hydrophilics Natural Products >100,000 types; tremendous variety of functions Some are made constitutively, others are induced Made in many cellular locations • Cytoplasm: most hydrophilics • Chloroplasts: terpenoids and some alkaloids Natural Products >100,000 types; tremendous variety of functions Some are made constitutively, others are induced Made in many cellular locations • Cytoplasm: most hydrophilics • Chloroplasts: terpenoids and some alkaloids • Mitochondria: some alkaloids and some amines Natural Products >100,000 types; tremendous variety of functions Some are made constitutively, others are induced Made in many cellular locations • Cytoplasm: most hydrophilics • Chloroplasts: terpenoids and some alkaloids • Mitochondria: some alkaloids and some amines • Peroxisomes: some terpenoids, convert glucosinolates to active form upon pathogen attack Natural Products >100,000 types; tremendous variety of functions Some are made constitutively, others are induced Made in many cellular locations • Cytoplasm: most hydrophilics • Chloroplasts: terpenoids and some alkaloids • Mitochondria: some alkaloids and some amines • Peroxisomes: some terpenoids, convert glucosinolates to active form upon pathogen attack • Endoplasmic reticulum: fatty acid derivatives, other nonpolars Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types • Some in all Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types • Some in all • Others in specialized cells or tissues Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types • Some in all • Others in specialized cells or tissues • Some are transported in xylem or phloem from site of synthesis to where they are stored Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types Many are stored in vacuole Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types Many are stored in vacuole Others in plastids or ER Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types Some are stored in special cell types, eg trichomes Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types Some are stored in special cell types Others in special cavities or ducts Secretory cavity in lemon Pine resin duct Natural Products >100,000 types; tremendous variety of functions Made in many cellular locations Made in many cell types Some are stored in special cell types Others in special cavities or ducts Others in flowers, leaves or fruits Natural Products >100,000 types; 3 main groups 1. Terpenoids 2. Alkaloids 3. Phenolics