Available online at www.sciencedirect.com
Transgenic plants for enhanced phytoremediation of toxic
explosives
Benoit Van Aken
Phytoremediation of organic pollutants, such as explosives, is
often a slow and incomplete process, potentially leading to the
accumulation of toxic metabolites that can be further
introduced into the food chain. During the past decade, plants
have been genetically modified to overcome the inherent
limitations of plant detoxification capabilities, following a
strategy similar to the development of transgenic crop.
Bacterial genes encoding enzymes involved in the breakdown
of explosives, such as nitroreductase and cytochrome P450,
have been introduced in higher plants, resulting in significant
enhancement of plant tolerance, uptake, and detoxification
performances. Transgenic plants exhibiting biodegradation
capabilities of microorganisms bring the promise of an efficient
and environmental-friendly technology for cleaning up polluted
soils.
Address
Department of Civil and Environmental Engineering, West Virginia
University, Morgantown, WV 26506, USA
Corresponding author: Van Aken, Benoit
([email protected])
Current Opinion in Biotechnology 2009, 20:231–236
This review comes from a themed issue on
Plant biotechnology
Edited by Dave Dowling and Sharon Lofferty Doty.
Available online 9th March 2009
0958-1669/$ – see front matter
# 2009 Elsevier Ltd. All rights reserved.
DOI 10.1016/j.copbio.2009.01.011
Introduction
Phytoremediation, or the use of plants for cleaning up
pollution, is a potentially attractive technology for the
treatment of soil contaminated by toxic chemicals, such as
nitro-substituted explosives and energetic compounds
[1,2]. Phytoremediation arose a few decades ago from
the recognition that plants were capable of metabolizing
toxic pesticides [3,4]. Today, bioremediation using plants
has acquired the status of a proven technology for the
treatment of heavy metal and organic-contaminated soils
[1,2]. However, unlike bacteria and mammals, plants are
autotrophic organisms that lack the enzymatic machinery
necessary for efficiently metabolizing organic compounds, often resulting in slow and incomplete remediation performance [5]. This led to the idea to modify
plants genetically by the introduction of bacterial or
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mammalian genes involved in the breakdown of toxic
chemicals. Although transgenic plants have not yet been
used in field applications, new advances, such as extension to more plant species, discovery of more catabolic
genes, and innovative transformation strategies, are likely
to deliver a technology that will improve phytoremediation efficiency and help control soil pollution [5,6,7].
This review summarizes recent advances in developing
plants specifically engineered for enhancing phytoremediation of explosives and energetic compounds.
Explosives as environmental contaminants
Best known for their explosives properties, nitro-substituted compounds, such as 2,4,6-trinitrotoluene (TNT),
hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and Glycerol trinitrate (GTN), are also toxic and persistent
environmental pollutants contaminating numerous military sites in Europe and North America (Figure 1). Manufacture of explosives, testing and firing on military
ranges, and decommission of ammunition stocks have
generated toxic wastes, leading to large-scale contamination of soils and groundwater [8,9]. From laboratory
studies, most nitro-substituted explosives were found to
be toxic for all classes of organisms, including bacteria,
algae, plants, invertebrates, and mammals [10–15]. TNT
and RDX are listed as ‘priority pollutants’ and ‘possible
human carcinogens’ by the U.S. Environmental Protection Agency (EPA) [11,16]. Physicochemical properties,
biodegradation, and toxicity of nitro-substituted explosives have been extensively reviewed in the literature
[8,9,17–19].
Traditional remediation of explosive-contaminated sites
requires soil excavation before treatment by incineration
or landfilling, which is costly, damaging for the environment, and, in many cases, practically infeasible owing to
the range of contamination [18]. As one of the ‘top ten
technologies for improving human health’ [20], bioremediation using microorganisms or plants represents an
attractive alternative for the treatment of explosive-contaminated sites. Different classes of microorganisms, including bacteria and fungi, are capable of transforming
energetic pollutants, which can be used as energy, carbon,
and/or nitrogen sources [8,9,19,21]. As a highly oxidized
molecule, TNT is easily reduced to form toxic amino
derivatives or a hydride Meisenheimer complex, further
transformed with the release of ammonium or nitrite
(Figure 2) [8,9]. However, except with white-rot fungi
that secrete powerful peroxidases, no significant mineralization of TNT has been reported in biological systems
Current Opinion in Biotechnology 2009, 20:231–236
232 Plant biotechnology
Figure 1
A few common nitro-substituted explosives: 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine (HMX), glycerol trinitrate (GTN), and pentaerythritol tetranitrate (PETN).
[19]. Initial biotransformation of RDX frequently
involves either direct enzymatic cleavage or single or
two-electron reduction of the nitro groups to form
unstable nitroso and hydroxylamino derivatives. In contrast to TNT, whose limiting degradation step is the
aromatic ring fission, a change in the molecular structure
of RDX results in ring collapse and the generation of
small aliphatic metabolites (Figure 2) [8,9,17].
Phytoremediation: clean-up of pollution with
plants
First developed for removal of heavy metals, phytoremediation has been used successfully for the treatment of a
variety of organic compounds, including chlorinated solvents, polyaromatic hydrocarbons, and explosives [1,2].
The main advantages of phytoremediation over other
remediation options include low installation and maintenance costs and no damaging impact on the environment. In addition, phytoremediation offers potential
beneficial side effects, such as carbon sequestration and
biofuel production [22,23]. As autotrophic organisms,
plants use sunlight and carbon dioxide as energy and
carbon sources and can be seen as natural, solar-powered,
pump-and-treat systems for cleaning up contaminated
environments [5]. Being exposed to a variety of natural
allelochemicals and xenobiotic compounds through the
root system, plants have developed diverse detoxification
mechanisms and have for long been recognized as capable
of metabolizing organic compounds [3,4,24].
Nitro-substituted explosives are efficiently taken up and
partially metabolized inside plant tissues [5,22,25]. The
Current Opinion in Biotechnology 2009, 20:231–236
detection of TNT metabolites, such as aminodinitrotoluene and aminodinitrobenzoate, suggests that plants can
carry out both reductive and oxidative transformation of
nitroaromatic compounds [21]. Identified RDX transformation products include reduction derivatives, such
as hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine, and a
range of breakdown products, such as 4-nitro-2,4-diazabutanal, formaldehyde, and nitrous oxide [26,27]. Experiments with [U-14C]RDX even showed a partial lightdependent mineralization by poplar plants [27]. The
detection of oxidation and reduction metabolites, as well
as large molecular weight products and non-extractable
fractions [28,29], suggests that plants metabolize explosives according to the ‘green liver’ model [4,30]. As in the
liver of mammals, detoxification by plants typically
involves three different phases: activation of the initial
toxic compound (phase I), conjugation with a molecule of
plant origin (phase II), and sequestration in plant organelles
or structures (phase III) (Figure 3).
Despite these promising observations, phytoremediation
suffers serious limitations, such as slow removal of pollutants from soil and the absence of significant detoxification, possibly leading to accumulation of toxic
metabolites inside plant tissues [5,31]. As a corollary
of their autotrophic metabolism – exogenous organic
compounds do not serve as electron donors – plants lack
the catabolic enzymes necessary to achieve full mineralization of organic molecules, potentially resulting in the
accumulation of toxic metabolites [5]. It was demonstrated that incomplete transformation of explosives in
poplar plants resulted in the release of toxic compounds
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Transgenic plants for enhanced phytoremediation of toxic explosives Van Aken 233
Figure 2
Simplified representation of the microbial degradation of the explosives, 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)
[8].
from plant tissues, potentially threatening the food chain
[32].
Transgenic plants for phytoremediation of
explosive compounds
There is great promise that transgenic plants expressing
bacterial or mammalian genes involved in xenobiotic
metabolism will improve the efficiency and safety of
phytoremediation, leading to a wider application in the
field [22]. Microbes and mammals are heterotrophic
organisms that possess the enzymatic machinery necessary to achieve a complete mineralization of organic molecules, complementing the metabolic capabilities of
plants [5]. Although the first transgenic plants developed for phytoremediation aimed to improve metal tolerance [33], the strategy has been extended to enhance
the plant metabolism of organic pollutants, such as explosives and halogenated compounds [34,35]. The use of
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transgenic plants for phytoremediation applications has
been reviewed recently in [5,6,18,34,36,37,38]. Transgenic plants developed for the remediation of explosives
are listed in Table 1.
In a pioneer work, French et al. [35] designed the first
transgenic plants specifically engineered for the phytoremediation of organic compounds [7]: tobacco plants
(Nicotania tabacum) were modified by the introduction
of a bacterial pentaerythritol tetranitrate (PETN)
reductase, an enzyme involved in the degradation of
nitrate esters and nitroaromatic explosives, and derived
from an Enterobacter cloacae previously isolated from an
explosive-contaminated soil [39]. PETN reductases are
bacterial flavonitroreductases that catalyze TNT degradation by either sequential reduction of nitro groups or
aromatic hydride addition, resulting in denitration
and, eventually, detoxification of TNT [21] (Figure 2).
Current Opinion in Biotechnology 2009, 20:231–236
234 Plant biotechnology
Figure 3
was lethal for wild-type seedlings. Recently, the same
transgenic system showed a reduction of TNT into 4hydroxylamino-2,6-dinitrotoluene and conjugation to
plant macromolecules to a greater extent in modified
plants as compared with the wild type [41]. Following
a similar strategy, Kurumata et al. [42] transformed Arabidopsis thaliana plants by the introduction of an E. coli
nitroreductase, NfsA, with activity against different
nitroaromatic compounds [42]. Plants expressing the bacterial transgene exhibited a 20-time higher nitroreductase
activity and 7–8 times higher TNT uptake compared
with wild-type plants. In addition, modified plants grew
on inhibiting TNT concentration (0.1 mM) and showed
in-tissue reduction of TNT into 4-amino-2,6-dinitrotoluene, which was not observed with wild-type organisms
[42]. These examples demonstrate that the introduction
of bacterial catabolic genes into plants significantly
improved their capability to take up and metabolize
the toxic explosive TNT.
The three phases of the ‘green liver’ model: hypothetical pathway
representing the metabolism of trinitrotoluene (TNT) in plant tissues:
phase I: activation of TNT by reduction to 2-amino-4,6-dinitrotoluene;
phase II: conjugation with a plant molecule, for example, glucose; phase
III: sequestration of the conjugate into the vacuole or cell wall [4].
Transgenic tobacco seeds were able to germinate and
grow in the presence of high concentrations of GTN
(1 mM) and TNT (0.5 mM), inhibiting for wild-type
seeds. In addition, transgenic plants exposed to 1 mM
GTN showed enhanced denitration compared with wildtype plants [35].
Together with flavonitroreductases, a large variety of
nitroreductases, including NfsA and NfsB of Escherichia
coli, PnrA of Pseudomonas putida, and NfsI from E. cloacae,
catalyzes the sequential reduction of TNT nitro groups to
hydroxylamino and amino derivatives, potentially followed by the release of ammonium through a Bamberger-like rearrangement (Figure 2). Hanninck et al. [40]
showed that transgenic tobacco constitutively expressing
the nitroreductase NfsI from E. cloacae removed high
amounts of TNT from the solution (100% of 0.25 mM
after 72 h), while only negligible amounts were removed
by wild-type plants. Transgenic plants were also able to
tolerate higher TNT concentrations, up to 0.5 mM, which
Besides TNT, plants were also transformed for improving
performances against RDX, which is today the most
widely used military explosive. A. thaliana plants were
engineered to express a bacterial gene, XplA, encoding a
RDX-degrading fused flavodoxin-cytochrome P450-like
enzyme [43,44]. The donor strain, Rhodococcus rhodochrous
strain 11Y, originally isolated from RDX-contaminated
soil, was capable of achieving a 30%-mineralization of
[U-14C]RDX in pure culture [44]. Rhodococcal bacteria
have been shown to degrade RDX by denitration, leading
to ring cleavage and the release of small aliphatic metabolites (Figure 2) [43]. Liquid cultures of A. thaliana
expressing XplA removed 32–100% of RDX (initial concentration 180 mM), while less than 10% was removed by
wild-type plants. When growing on RDX-contaminated
soil, the transgenic lines showed no phytotoxic effect up
to 2000 mg kg 1, while significant inhibition was
observed in wild type at 250 mg kg 1. Conversely,
RDX analysis in exposed plants showed significantly
higher concentrations in wild-type plants, suggesting that
transgenic lines were capable of more efficient transformation of RDX.
Although A. thaliana and tobacco are well characterized,
laboratory model plants, they are not well adapted for
phytoremediation applications, given their small stature
Table 1
Transgenic plants engineered for the transformation of explosives.
Gene
Pentaerythritol tetranitrate reductase
Nitroreductase
Nitroreductase
Cytochrome P450
Nitroreductase
Source
Plant
Enterobacter cloacae
Enterobacter cloacae
Escherichia coli
Rhodococcus rhodochrous
Pseudomonas putida
Nicotania tabacum
Nicotania tabacum
Arabidopsis thaliana
Arabidopsis thaliana
Populus tremula Populus
tremuloides
Current Opinion in Biotechnology 2009, 20:231–236
Target pollutant
References
GTN and TNT
TNT
TNT
RDX
TNT
[35]
[40,41]
[42]
[43]
[46]
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Transgenic plants for enhanced phytoremediation of toxic explosives Van Aken 235
and shallow root system. Poplar and aspen (Populus sp.),
on the contrary, are widely distributed, fast-growing, high
biomass plants ideal for phytoremediation applications
[45]. Recently, a transgenic hybrid aspen (P. tremula P.
tremuloides) expressing a nitroreductase gene from P.
putida, PnrA, was shown to tolerate and take up greater
amounts of TNT from contaminated waters and soil
compared with wild-type plants [46]. Using [U-ring
13
C]TNT, the authors showed a rapid adsorption of
TNT on the root surface, followed by a slow entrance
into the plant, with most [13C]carbon remaining in the
roots.
The few examples above demonstrate that introduction
of bacterial genes involved in explosive degradation
improves phytoremediation performances by at least
three different ways: increasing degradation, plant tolerance, and uptake of toxic compounds. The later effect,
observed with explosives and chlorinated solvents, is
likely to be related to a reduced phytotoxicity and a
steeper gradient of pollutant concentration inside plant
tissues [34,35].
Introduction of exogenous genes involved in xenobiotic
transformation can induce unexpected side effects, such
as an enhancement of the rhizosphere microfloral activity.
Travis et al. [47] have recently reported that transgenic
tobacco plants overexpressing type I nitroreductase gene
from E. cloacae were able to detoxify TNT in soil,
resulting in increased microbial biomass and metabolic
activity in the rhizosphere of transgenic plants as compared with wild-type plants.
Acknowledgements
The author is grateful to the Strategic Environmental Research and
Development Program (SERDP; award numbers 02 CU13-17 and ER-1499)
and West Virginia University Research Corporation (PSCoR Award).
References and recommended reading
Papers of particular interest, published within the period of review,
have been highlighted as:
of special interest
of outstanding interest
1.
Salt D, Smith R, Raskin I: Phytoremediation. Annu Rev Plant
Physiol Plant Mol Biol 1998, 49:643-668.
2.
Schnoor J, Licht L, McCutcheton S, Wolfe N, Carreira L:
Phytoremediation of organic and nutrient contaminants.
Environ Sci Technol 1995, 29:318A-323A.
3.
Cole DJ: Oxidation of xenobiotics in plants. Prog Pest Biochem
Toxicol 1983, 3:199-253.
4.
Sandermann H: Higher plant metabolism of xenobiotics: the
‘green liver’ concept. Pharmacogenetics 1994, 4:225-241.
5.
Eapen S, Singh S, D’Souza SF: Advances in development of
transgenic plants for remediation of xenobiotic pollutants.
Biotechnol Adv 2007, 25:442-451.
This excellent review focuses on recent developments of transgenic
plants for remediation of organic pollutants, including explosives, chlorinated compounds, petroleum products, PCBs, and pesticides. The paper
includes tables summarizing the phytoremediation of organic pollutants
by both natural and engineered plants.
6.
7. Doty SL: Enhancing phytoremediation through the use of
transgenics and endophytes. New Phytol 2008, 179:318-333.
This review examines recent advances in enhancing phytoremediation of
organic pollutants and heavy metals through both the development of
transgenic plants and the use of symbiotic endophytic microorganisms
within plant tissues.
8.
Hawari J, Beaudet S, Halasz A, Thiboutot S, Ampleman G: Microbial
degradation of explosives: biotransformation versus
mineralization. Appl Microbiol Biotechnol 2000, 54:605-618.
9.
Spain JC: Biodegradation of nitroaromatic compounds.
Annu Rev Microbiol 1995, 49:523-555.
Conclusions
Enhancing phytoremediation through genetic transformation of plants has become a proven technology that will
help overcome the major limitation inherent to the process, that is, the threat that accumulated toxic compounds
would contaminate the food chain. Further developments
will involve the introduction of broad-substrate, natural or
engineered, catabolic genes, such as mammalian cytochrome P450 or fungal peroxidase, for the simultaneous
remediation of a variety of pollutants, as commonly found
in contaminated sites [6]. Similarly, the introduction of
multiple transgenes involved in different bioremediation
processes, for example, uptake by roots and metabolic
phases of the ‘green liver’ model, will bring further
promises of an efficient and environmental-friendly technology for cleaning up polluted soils. Another important
barrier to field application of transgenic plants for bioremediation arises from the true or perceived risk of
horizontal gene transfer to related wild or cultivated
plants. Therefore, it is likely that the next generation
of transgenic plants will involve systems preventing such
a transfer, for instance by the introduction of transgenes
into chloroplastic DNA or the use of conditional lethality
genes [48].
www.sciencedirect.com
Cherian S, Oliveira MM: Transgenic plants in phytoremediation:
recent advances and new possibilities. Environ Sci Technol
2005, 39:9377-9390.
10. Honeycutt ME, Jarvis AS, McFarland VA: Cytotoxicity and
mutagenicity of 2,4,6-trinitrotoluene and its metabolites.
Ecotoxicol Environ Saf 1996, 35:282-287.
11. Lachance B, Robidoux PY, Hawari J, Ampleman G, Thiboutot S,
Sunahara GI: Cytotoxic and genotoxic effects of energetic
compounds on bacterial and mammalian cells in vitro. Mutat
Res 1999, 444:25-39.
12. Robidoux PY, Bardai G, Paquet L, Ampleman G, Thiboutot S,
Hawari J, Sunahara GI: Phytotoxicity of 2,4,6-trinitrotoluene
(TNT) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine
(HMX) in spiked artificial and natural forest soils. Arch Environ
Contamin Toxicol 2003, 44:198-209.
13. Smock LA, Stoneburner DL, Clark JR: The toxic effects of
trinitrotoluene (TNT) and its primary degradation products on
two species of algae and the fathead minnow. Water Res 1976,
10:537-543.
14. Sunahara GI, Dodard S, Sarrazin M, Paquet L, Hawari J, Greer CW,
Ampleman G, Thiboutot S, Renoux AY: Ecotoxicological
characterization of energetic substances using a soil
extraction procedure. Ecotoxicol Environ Saf 1999, 43:138-148.
15. Talmage SS, Opresko DM, Maxwell CJ, Welsh CJ, Cretella FM,
Reno PH, Daniel FB: Nitroaromatic munitions compounds:
environmental effects and screening values. Rev Environ
Contam Toxicol 1999, 161:1-156.
16. Keith LH, Telliard WA: Priority pollutants: a perspective view.
Environ Sci Technol 1979, 13:416-423.
Current Opinion in Biotechnology 2009, 20:231–236
236 Plant biotechnology
17. Crocker FH, Indest KJ, Fredrickson HL: Biodegradation of the
cyclic nitramine explosives RDX, HMX, and CL-20. Appl
Microbiol Biotechnol 2006, 73:274-290.
18. Hannink NK, Rosser SJ, Bruce NC: Phytoremediation of
explosives. CRC Crit Rev Plant Sci 2002, 21:511-538.
19. Van Aken B, Agathos SN: Biodegradation of nitro-substituted
explosives by white-rot fungi: a mechanistic approach. Adv
Appl Microbiol 2001, 48:1-77.
20. Daar AS, Thorsteinsdottir H, Martin DK, Smith AC, Nast S,
Singer PA: Top ten biotechnologies for improving health in
developing countries. Nat Gen 2002, 32:229-232.
21. Ramos JL, Gonzalez-Perez MM, Caballero A, van Dillewijn P:
Bioremediation of polynitrated aromatic compounds: plants
and microbes put up a fight. Curr Opin Biotechnol 2005,
16:275-281.
22. Dietz A, Schnoor J: Advances in phytoremediation. Environ
Health Perspect 2001, 109:163-168.
23. Doty SL, James CA, Moore AL, Vajzovic A, Singleton GL, Ma C,
Khan Z, Xin G, Kang JW, Park AY et al.: Enhanced
phytoremediation of volatile environmental pollutants
with transgenic trees. Proc Natl Acad Sci U S A 2007,
104:16816-16821.
24. Singer A: The chemical ecology of pollutants biodegradation.
In Phytoremediation and Rhizoremediation: Theoretical
Background. Edited by Mackova M, Dowling D, Macek T. Springer;
2006:5-21.
25. Burken JG, Shanks JV, Thompson PL: Phytoremediation and
plant metabolism of explosives and nitroaromatic
compounds. In Biodegradation of Nitroaromatic Compounds and
Explosives. Edited by Spain JC, Hughes JB, Knackmuss H-J.
Lewis Publisher; 2000:239-276.
26. Just CL, Schnoor JL: Phytophotolysis of hexahydro-1,3,5trinitro-1,3,5-triazine (RDX) in leaves of reed canary grass.
Environ Sci Technol 2004, 38:290-295.
27. Van Aken B, Yoon JM, Just CL, Schnoor JL: Metabolism and
mineralization of hexahydro-1,3,5-trinitro-1,3,5-triazine inside
poplar tissues (Populus deltoides x nigra DN-34). Environ Sci
Technol 2004, 38:4572-4579.
28. Brentner LB, Mukherji ST, Merchie KM, Yoon JM, Schnoor JL, Van
Aken B: Expression of glutathione S-transferases in poplar
trees (Populus trichocarpa) exposed to 2,4, 6-trinitrotoluene
(TNT). Chemosphere 2008, 73:657-662.
This paper describes the overexpression of glutathione S-transferases in
poplar plants exposed to the explosive TNT. In addition, evidence of
conjugation of TNT with glutathione was demonstrated in vitro using a
mammalian glutathione S-transferase.
29. Gandia-Herrero F, Lorenz A, Larson T, Graham IA, Bowles DJ,
Rylott EL, Bruce NC: Detoxification of the explosive 2,4,6trinitrotoluene in Arabidopsis: discovery of bifunctional O- and
C-glucosyltransferases. Plant J 2008, 56:963-974.
This paper describes the discovery of glycosyltransferases genes overexpressed in Arabidopsis thaliana plants exposed to TNT. Recombinantly
expressed glycosyltransferases were showed to catalyze the conjugation
of TNT with glucose, suggesting the implication of the enzymes in TNT
detoxification by plants.
30. Burken J: Uptake and metabolism of organic compounds:
green-liver model. In Phytoremediation: Control and Transport of
Contaminants. Edited by McCutcheon S, Schnoor J. John Wilez;
2003:499-528.
31. Pilon-Smits E: Phytoremediation. Annu Rev Plant Biol 2005,
56:15-39.
32. Yoon JM, Van Aken B, Schnoor JL: Leaching of contaminated
leaves following uptake and phytoremediation of RDX, HMX,
and TNT by poplar. Int J Phytorem 2006, 8:81-94.
33. Misra S, Gedamu L: Heavy-metal tolerant transgenic Brassica
napus L. and Nicotiana tabacum L. plants. Theor Appl Genet
1989, 78:161-168.
34. Doty SL, Shang TQ, Wilson AM, Tangen J, Westergreen AD,
Newman LA, Strand SE, Gordon MP: Enhanced metabolism of
Current Opinion in Biotechnology 2009, 20:231–236
halogenated hydrocarbons in transgenic plants containing
mammalian cytochrome P450 2E1. Proc Natl Acad Sci U S A
2000, 97:6287-6291.
35. French CE, Rosser SJ, Davies GJ, Nicklin S, Bruce NC:
Biodegradation of explosives by transgenic plants expressing
pentaerythritol tetranitrate reductase. Nat Biotechnol 1999,
17:491-494.
36. Macek T, Kotrba P, Svatos A, Novakova M, Demnerova K,
Mackova M: Novel roles for genetically modified plants in
environmental protection. Trends Biotechnol 2008, 26:146-152.
This short review discusses new developments of transgenic plants for
general environmental applications, including pollution prevention (e.g.
reduced pesticide use) and phytoremediation.
37. Rosser SJ, French CE, Bruce NC: Engineering plants for the
phytodetoxification of explosives. In Vitro Cell Dev Biol Anim
Plant 2001, 37:330-333.
38. Rugh CL: Genetically engineered phytoremediation: one man’s
trash is another man’s transgene. Trends Biotechnol 2004,
22:496-498.
39. French CE, Nicklin S, Bruce NC: Aerobic degradation of 2,4,6trinitrotoluene by Enterobacter cloacae PB2 and by
pentaerythritol tetranitrate reductase. Appl Environ Microbiol
1998, 64:2864-2868.
40. Hannink N, Rosser SJ, French CE, Basran A, Murray JAH,
Nicklin S, Bruce NC: Phytodetoxification of TNT by transgenic
plants expressing a bacterial nitroreductase. Nat Biotechnol
2001, 19:1168-1172.
41. Hannink NK, Subramanian M, Rosser SJ, Basran A, Murray JAH,
Shanks JV, Bruce NC: Enhanced transformation of TNT by
tobacco plants expressing a bacterial nitroreductase.
Int J Phytorem 2007, 9:385-401.
42. Kurumata M, Takahashi M, Sakamoto A, Ramos JL, Nepovim A,
Vanek T, Hirata T, Morikawa H: Tolerance to, and uptake and
degradation of 2,4,6-trinitrotoluene (TNT) are enhanced by the
expression of a bacterial nitroreductase gene in Arabidopsis
thaliana. Z Naturforsch [C] 2005, 60:272-278.
43. Rylott EL, Jackson RG, Edwards J, Womack GL, Seth-Smith HMB,
Rathbone DA, Strand SE, Bruce NC: An explosive-degrading
cytochrome P450 activity and its targeted application for the
phytoremediation of RDX. Nat Biotechnol 2006, 24:216-219.
44. Seth-Smith HMB, Rosser SJ, Basran A, Travis ER, Dabbs ER,
Nicklin S, Bruce NC: Cloning, sequencing, and characterization
of the hexahydro-1,3,5-trinitro-1,3,5-triazine degradation
gene cluster from Rhodococcus rhodochrous. Appl Environ
Microbiol 2002, 68:4764-4771.
45. Schnoor J: Degradation by plants - Phytoremediation. In
Biotechnology, vol 11b, edn 2. Edited by Rehm H-J, Reed G.
Wiley-VCH; 2000:371–384.
46. van Dillewijn P, Couselo JL, Corredoira E, Delgado A, Wittich RM,
Ballester A, Ramos JL: Bioremediation of 2,4,6-trinitrotoluene
by bacterial nitroreductase expressing transgenic aspen.
Environ Sci Technol 2008, 42:7405-7410.
This paper describes the transformation of Arabidopsis thaliana plants
by the introduction of an Escherichia coli NfsA nitroreductase, with
activity against different nitroaromatic compounds. Transgenic plants
showed higher nitroreductase activity, TNT tolerance, and TNT uptake
compared with wild-type plants. The paper also showed a reduction of
TNT into 4-amino-2,6-dinitrotoluene, which was no observed with wildtype organisms.
47. Travis ER, Hannink NK, Van der Gast CJ, Thompson IP, Rosser SJ,
Bruce NC: Impact of Transgenic tobacco on trinitrotoluene
(TNT) contaminated soil community. Environ Sci Technol 2007,
41:5854-5861.
This paper shows that transgenic tobacco plants overexpressing a
bacterial nitroreductase gene detoxified soil contaminated with TNT,
resulting in significantly increased microbial biomass and activity in the
rhizosphere compared with wild-type plants.
48. Davison J: Risk mitigation of genetically modified bacteria and
plants designed for bioremediation. J Ind Microbiol Biotechnol
2005, 32:639-650.
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