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Biotecnologie ambientali Phytoremediation (fitodepurazione)

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1 Biotecnologie ambientali Phytoremediation (fitodepurazione)

2 Le piante coltivate e la sindrome da domesticazione: shattering e dormienza Rischi e benefici ambientali delle piante transgeniche in paragone a quelle convenzionali. Convenzione di Rio, Protocollo di Cartagena e normativa sulle piante create tramite ingegneria genetica Piante per una maggiore sostenibilità ambientale (es. plastiche biodegradabili), per il risanamento (fitodepurazione) e come biosensori di contaminazione. Interazione pianta-microrganismo: le risposte di difesa delle piante e generazione di specie resistenti. Interazione simbiotiche pianta-microrganismo: fissazione dellazoto (batteri azoto fissatori) ed efficienza nella nutrizione minerale (funghi vescicolo arbuscolari) PROGRAMMA

3 Phytoremediation: to remediate polluted soil and/or water with plants. An alternative to landfill disposal or physical / chemical processing. Present strategies: Bioaccumulation (transport and storage for harvest) Bioprocessing (chemical transformation to CO 2, NH 3, Cl - & SO 4 2- ) Advantages of plants: Plants demonstrate tolerance to toxins Photosynthesis-free energy Extensive root systems to mine soil (440 million km/h/yr** ) Selective transport of materials out of water/soil Large biomass for harvesting Species adapted to different ecosystems including wetlands Disadvantages of plants: Transgenics & their envoronmental release

4 Tipi of fitodepurazione 1.Phytoextraction - uptake of substances from the environment, with storage in the plant (also known as phytoaccumulation). 2. Phytostabilization - reducing the movement or transfer of substances in the environment, for example, limiting the leaching of soil contaminants. 3. Phytostimulation - enhancement of microbial activity for the degradation of contaminants, typically around plant roots. 4. Phytotransformation - uptake of substances from the environment, with degradation occurring within the plant (phytodegradation). 5. Phytovolatilization - removal of substances from the soil or water with release into the air, possibly after degradation. 6. Rhizofiltration - the removal of toxic materials from groundwater through root activity.

5 From Pilon-Smits (2005) Annu Rev Plant Biol 56: Mercury Selenium TCE, PCE Heavy metals Se, As Radionuclides TCE/PCE... Organics (PCBs, PAHs) Phytodegradation Herbicides, TNT, MTBE, TCE Nonbiological remediation technologies and bio/phytoremediation are not mutually exclusive.

6 Pollution Heavy metals Phosphate Arsenate Nitrogen Insecticides Herbicides PCBs, TCE,... Radionuclides Classification A major distinction between elemental and organic pollutants: Most organic pollutants can be mineralized, while elements cannot. Source Agriculture (pesticides, herbicides, irrigation water), mining, transport, spills (fuel, solvents), military activities (explosives, chemical weapons), industry (chemical, petrochemical), wood treatment...

7 Examples in detail Phytoextraction (As/ H3PO4/ metals) Phytodegradation/Phytotransformation Phytodegradation of explosives Phytodetoxification of mercuric Because biological processes are ultimately solar-driven, phytoremediation is on average tenfold cheaper than engineering-based remediation methods such as soil excavation, soil washing or burning, or pump-and-treat systems. Phytoremediation is usually carried out in situ contributes to its cost-effectiveness and may reduce exposure of the polluted substrate to humans, wildlife, and the environment.

8 Bioaccumulation of Arsenic the 20th most common element in the earths crust and the 12th most common element in the human body. Arsenic is a major worldwide contaminant that can arise through industrial activity (pesticides, mining, combustion etc.) or from soil and ground water. Associated with acute poisoning and linked to liver, lung, kidney, bladder cancer; cause skin lesions; damage to the nervous system. Physical remediation (resins etc.)

9 Bioaccumulation of Arsenic In India and Bangladesh (around the Bay of Bengal) ~400 million people are at risk of arsenic poisoning, and up to 40 million people drink well water containing toxic levels of arsenic. Limite per l'arsenico proposto dall'OMS e valido per gli USA è di 0.01 mg/L (10 μg/L, 10 ppb). Limite europeo ammesso per il Glifosate (per la potabilità): 0.1 ppb

10 Bioaccumulation As/Hg: General Strategy (Meagher & Heaton, 2005)

11 Bioaccumulation of Arsenic Strategy behind cloning bacterial arsenate reductase (ArsC) catalyzes reduction of arsenate to arsenite. bacterial γ-glutamylcysteine synthetase (γ-ECS) catalyzes the formation of γ -glutamylcysteine ( γ -EC) from glutamate and cys for synthesis of glutathione (GSH) and phytochelatins (PCs; three arrows) reduced arsenite can bind organic thiols (RS) such as those in γ -EC, GSH, and PCs. Then transfer to vacuole. Dhankher, et al. (2002) Arabidopsis engineered to hyperaccumulate arsenic arsenate reductase γ-glutamylcysteine synthetase

12 Bioaccumulation of Arsenic The prokaryotic arsC gene has been previously shown to confer resistance in the eukaryote Saccharomyces cerevisiae

13 The bacterial ArsC enzyme was expressed under control of the soybean ribulose bisphosphate carboxylase small-subunit (rubisco) SRS1 gene promoter, which shows strong light-induced expression in leaves and stems. Comparative growth inhibition of three SRS1p/ArsC lines % relative concentration of free AsO 4 3-, AsO 3 3-, and As(III) tris-GSH in leaves

14 I doppi trasformanti resistono a concentrazioni di arseniato più alte Comparative growth of two hybrid lines, the parental lines expressing either ArsC or γ-ECS alone, and (WT) grown for 3 weeks on NaAsO 3

15 Arsenic contamination: removed by phytoextraction The Chinese Ladder fern Pteris vittata, also known as the brake fern, is a highly efficient accumulator of arsenic. P. vittata grows rapidly and can absorb up to 2% of its weight in arsenic... When grown on soil with 100 ppm not only did it absorb more arsenic, but it grew 40% larger than normal. Lena Q. Ma, 2001 P. vittata, a natural arsenic hyperaccumulator, can tolerate soil concentrations of 1,500 μg arsenate/g and can accumulate up to 23 mg arsenic/g in its shoots (fronds). The striking difference between P. vittata and arsenic non-accumulators is the enormous transport of arsenic from roots to shoots in P. vittata. In most plants, only a small fraction of the arsenic taken up from soil by roots accumulates in the above-ground tissue (<20%), whereas P. vittata accumulates up to 95% of the arsenic in above-ground tissue.

16 PLANTSMETAL CONCENTRATION (mg metal /kg dry matter) Eichhornia crassipesFe14400 Thlapsi caerulescensZn(roots)25000 Minuartia vernaCu(roots) Pb(roots) Cd(leaves) Jasione montanaAs (leaves)3100 Mechovia grandifloraMn(leaves)7000 Acrocephalus robertiiCo(leaves)1490 Psychotria douarreiNi (roots)92000 Pearsonia metalliferaCr (roots)1620 Astragalus preussiU(leaves, roots)70 Astragalus acemosusSe(leaves)15000 Alyssum bertholoniiNi(shoots)13400 Miconia lutescensAl (shoots)6800

17 Heavy metal hyperaccumulators Thlaspi montanum var. montanum, a Ni-hyperaccumulator plant that grows on Serpentine soils, research of Martha Palamino, IB graduate student (UC Berkeley).

18 Pteris vittata Brassica juncea Thlaspi caerulescens Alyssum serpyllifolium Hyperaccumulator plants

19 Phytoextraction of excess nutrients: Pig slurry cleanup Using duckweed (Lemna)

20 Rhizofiltration using Arundo donax Sewage and urban wastewaters Halogenated residues (USA) N, P and S rich wastewaters (for nutrient stripping) Saline waste waters (reduce volumes by transpiration thru Adx to grow biomass) Intensive root system (Marton and Czako, USA)

21 Song et al., (2003) Nat Biotechnol. 21:914-9.

22 YCF1 confers Pb(II) and Cd(II) resistance to yeast Il mutante nullo ycf1 di lievito è più sensibile a Pb 2+ e Cd 2+ Il mutante sovraesprimente YCF1 è più resistente a Pb 2+ e Cd 2+ Il mutante sovraesprimente YCF1 presenta molto più mRNA

23 La sovraespressione di YCF1 in lievito porta un maggior accumulo di Pb e Cd PbCd YCF1 è presente nella membrana plasmatica e vacuolare brightfield Fluorescence of GFP-YCF1 FM4-64 stains plasma (top) and vacuolar (bottom) membranes

24 c RT-PCR su Arabidopsis che esprime YCF1 Southern blot sulla RT-PCR brightfield Fluorescence of GFP-YCF1. GFP-YCF1 espresso in protoplasti di A. thaliana è localizzato sulla membrana plasmatica e vacuolare

25 Arabidopsis transgenica per YCF1 mostra una maggior resistenza a a Pb 2+ e Cd 2+ Generazione T2 Crescono meglio (maggior biomassa)

26 Il contenuto espresso in μg/pianta è più efficace Il contenuto per g di peso fresco non è molto diverso, ma ci deve essere una diversa localizzazione Vacuoli isolati dal trasformante accumulano più coniugati di GS-Cd

27 The location : a base-metal smelter, South Africa The solution : phytoextraction using a native nickel-accumulating species The problem : Ni contamination over 5ha due to Ni salt storage and spillage Phytoextraction in action Accumulatrici naturali vengono trapiantate sul terreno contaminato La biomassa viene poi bruciata

28 Phytoextraction for gold Thio-ligands can induce the solubility and uptake of gold from waste, low-grade rock Discovery made in New Zealand Proof of concept achieved and the technology is being field tested Aim is a crop of 10 t/ha biomass with 100 mg/kg gold concentration dry weight This will yield 1000 g of gold per hectare as well as other metals made soluble Current focus is on mercury (Hg) removal at the same time as gold

29 Biodegredation of Organomercury Methylmercury is a pollutant that biomagnifies in the aquatic food chain with severe consequences for humans and other animals. The main targets include free cysteine in proteins and peptides leading to damage in the central nervous system. Symptoms include sensory impairment (vision, hearing, speech), disturbed sensation and a lack of coordination. Mercury occurs in deposits throughout the world and it is harmless in an insoluble form, such as mercuric sulfide, but it is poisonous as methylmercury [CH3Hg]+ due to its aqueous solubility. Sources of Mercury include burning coal and mineral extraction. Many uses of mercury are being curtailed or eliminated.

30 Phytostabilization of mercury by willow roots Yaodong Wang, 2004

31 Phytodetoxification of mercuric compounds merB merA/merB merA control Bizily, S., Rugh, C., Meagher, R. (2000) Phytodetoxification of hazardous organomercurials by genetically engineered plants. Nature Biotechnology. 18: Rugh, C.Meagher, R. Methylmercury is found in wetlands and aquatic sediments worldwide. Both ionic mercury and methylmercury are absorbed in the gastrointestinal tract of animals, but methylmercury is retained much longer in the body and is, therefore, is carried up through the food chain more efficiently. Plants engineered with both the merA and merB genes should be able to extract methylmercury from contaminated environments and transpire Hg(0) into the atmosphere. Because Hg(0) resides in the atmosphere for approximately two years, transpired Hg(0) will be diluted to much lower concentrations before being redeposited into terrestrial waters and sediments rather than being concentrated in one area. Additionally the amount of Hg(0) emitted from sites undergoing phytovolitalization can be regulated and will most likely be small in comparison to the concentrations of Hg(0) already in the atmosphere.

32 Rhizofiltration: sunflowers after Chernobyl disaster Plants on rafts in pondwater: removed radionuclides of strontium, cesium, etc.

33 Tolerance mechanisms for inorganic and organic pollutants in plant cells. Detoxification generally involves conjugation followed by active sequestration in the vacuole and apoplast, where the pollutant can do the least harm. Chelators shown are GSH: glutathione, Glu: glucose, MT: metallothioneins, NA: nicotianamine, OA: organic acids, PC: phytochelatins. Active transporters are shown as boxes with arrows. I contaminanti organici sono spesso biodegradati

34 Breakdown of contaminants taken up by plants through metabolic processes within or external to plant through effect of compound produced by plants Oxidoreductases, dehalogenases, nitroreductases, peroxidases, nitrilases & laccases may involved Phytodegradation/Phytotransformation

35 Phytodegradation of pesticides by a notorious pest plant The potential of water hyacinth (Eichhornia crassipes) to remove a phosphorus pesticide ethion were investigated. The disappearance rate constants of ethion... implied that plant uptake and phytodegradation contributed 69% and that of microbial degradation took up 12% to the removal of the applied ethion. The accumulated ethion in live water hyacinth plant decreased by 55-91% in shoots and 74-81% in roots after the plant growing 1 week in ethion free culture solutions, suggesting that plant uptake and phytodegradation might be the dominant process for ethion removal by the plant. This plant might be utilized as an efficient, economical and ecological alternative to accelerate the removal and degradation of agro-industrial wastewater polluted with ethion. Xia H, Ma X. (2006) Phytoremediation of ethion by water hyacinth (Eichhornia crassipes) from water. Bioresour Technol May;97(8):

36 Phytodegradation of TCE, other chlorinated hydrocarbons by hybrid and/or transgenic poplar A MASS BALANCE FIELD TRIAL OF CARBON TETRACHLORIDE PHYTOREMEDIATION USING POPLAR: PHYTODEGRADATION IS THE LIKELY FATE Michael Dossett1, and Xiaoping Wang2, and Stuart E. Strand3

37 Cl Cl Cl O C=C C C CO2 + Cl2 H Cl Cl2 H O CH3 NO2 CH3 NH3 + NO2 NH3 + CO2 + NH4 + NO2 NH3 + Trichloroethylene Chloroacetate Trinitrotoluene Triaminotoulene -

38 Biodegradation of explosives The Problem: Contamination to explosives TNT, RDX and glycerol trinitrate. Exposure to TNT and RDX, and their degradation products causes symptoms such as anemia and liver damage. These chemicals can be lethal and are suspected carcinogens. Hundreds of tons of these compounds are found in sediments at innumerable manufacturing sites and storage sites for unexploded ordnance around the world. Tens of thousands of acres of land and water resources are unsafe because of RDX and TNT contamination. The Solution: Engineer plants that are able to degrade these compounds in situ.

39 Biodegradation of explosives These are the targets Breakdown of TNT to ADNT (monoaminodinitrotoluene) can create sterile pink water lagoons.

40 Biodegradation of explosives: The general strategy is to isolate catabolic genes and through standard cloning technologies convert them into plant genes expressed via a constitutive promoter such as the CaMV 35S promoter for expression throughout the plant. tissue-specific promoter for expression to leaves, stems etc. Following transformation and plant regeneration, the properties of the plant are evaluated by standard tests. Bacteria are the usual source of the genes, bacteria such as Enterobacter cloacae or Rhodococcus rhodochrous that can grow on these contaminants.

41 Biodegradation of explosives: Summary from Meagher (2006). Key: RDX, TNT, ADNT: See Fig 6 NR: nitroreductase XplA: RDX-degrading cytochrome P450 NDAB: 4-nitro-2,4-diazabutanal.

42 Lane 1, molecular weight marker; Lane 2, solubilized recombinant protein; Lane 3, affinity purified XplA. (c) UV-visible absorbance spectra of purified XplA: oxidized; sodium dithionite reduced; reduced bubbled with carbon monoxide. (d) UV-visible absorbance spectra of extracted flavin cofactor. (e) Activity of purified protein under anaerobic conditions. Solid shapes, active XplA; open shapes, boiled XplA. Proposed RDX breakdown pathway Protein purification on 10% SDS-PAGE.

43 Biodegradation of explosives: from Rylott et al. (2006) Conclusion from these experiments: decontamination works in a model system TNT can be catabolized RDX is catabolized and the nitrogen used for growth (win-win!!)

44 Transcriptional Profiling: Arabidopsis Thaliana Root Responses to Explosives TNT ( Trinitrotoluene ) RDX ( Hexahydro-1,3,5-trinitro-1,3,5-triazine ) cytochrome P450, putative putative transcription factor similar to bacterial tolB proteins NAM, no apical meristem, - like protein monodehydroascorbate reductase-like putative ser/thr-protein kinase transporter-like protein Carbamoyl-P synthetase small subunit MYB like protein putative glutathione transferase (TCCCCTATTA) no matches in genome alpha-hydroxynitrile lyase-like protein vacuolar H+-ATPase subunit H (VHA-H) putative 3-dehydroquinate synthase putative peroxidase gamma-VPE (vacuolar processing enzyme) DnaJ-like protein NPR1-like protein SAGESerial Analysis of Gene Expression tags Very different metabolism Le reazioni di detossificazione seguono il modello del green liver di Sandermann putative transcription factor vacuolar H+-transporting ATPase 16K chain P2 I geni indotti sono ottimi candidati per la sovraespressione

45 Jackson et al., (2007) Exploring the biochemical properties and remediation applications of the unusual explosive-degrading P450 system XplA/B. PNAS 104:16822– E possibile sfruttare i sistemi degradativi scoperti nei batteri o altri microrgansmi e introdurli nelle piante

46 Uptake and metabolic use of cyanide by willows Transport and metabolism of free cyanide and iron cyanide complexes by willow S. EBBS1, J. BUSHEY2, S. POSTON1, D. KOSMA1, M. SAMIOTAKIS1 & D. DZOMBAK

47 Remediation of saline soils Salicornia (pickleweed) accumulates salt in vacuole. A form of table salt can then be extracted from plant.

48 Aluminium detoxification: Gene for citrate synthase used for production of transgenic plants produce higher level of citrate & secrete it into the soil through roots,which bind with Aluminium which is incapable of entering roots E.g tobacco, papaya, rice & corn TNT detoxification: Transgenic tobacco produced by transformation with nitroreductase gene nfs1 isolated from Enterobacter cloacae can tolerate high TNT conc.

49 The most important single act of phytoremediation? 6 CO H 2 O C 6 H 12 O O 2 In sintesi: tanta ricerca, tanti risultati interessanti ma per ora non ci sono prodotti commerciali e vista lattuale situazione normativa difficilmente se ne vedranno

50 Song et al. (2003) Engineering tolerance and accumulation of lead and cadmium in transgenic plants. Nat. Biotech. Ghosh Moyukh, Singh S.P,Trivedy R.K, Sharma Sadhana(Eds) 2005 Phytoremediation of heavy metal contaminated soils:role of natural & synthetic chelatins,Biotechnological applications in environmental management,B.S.publication. Sharma J., Saini V., Singh A., Singh N., Trivedy R.K, Sharma S. (Eds) (2005) Phytoremediation of organic pollutants, Biotechnological applications in environmental management, B.S.publication. Kumar R., Sharma J., Gaur P.,Trivedy R.K, Sharma Sadhana (Eds) 2005 Phytoremediation of soil contaminated with heavy metals,Biotechnological applications in environmental management,B.S.publication. Singh B.D Biotechnology Expanding horizon, Kalyani Publishers 2008 Mc Grath S.P, Zhao F.J (2003) Phytoextraction of metal and metalloid from contaminated soil, current opinion in Biotechnology 14: Richard B Meagher (2000) Phytoremediation of toxic elemental and organic pollutants. Current opinion in plant biology 20003:435. Singh J.S, Singh S.P, Gupta S.R, Ecology Environment and Resources Conservation, Anamaya publishers Rao et al., (2009) Phytoremediation and phytosensing of chemical contaminants, RDX and TNT: identification of the required target genes. Funct Integr Genomics. ??? Bibliografia

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