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Greatly Enhanced Removal of Volatile Organic Carcinogens by a Genetically Modified Houseplant, Pothos Ivy ( Epipremnum aureum ) Expressing the Mammalian Cytochrome P450 2e1 Gene


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The indoor air in urban homes of developed countries is usually contaminated with significant levels of volatile organic carcinogens (VOCs), such as formaldehyde, benzene, and chloroform. There is a need for a practical, sustainable technology for the removal of VOCs in homes. Here we show that a detoxifying transgene, mammalian cytochrome P450 2e1 can be expressed in a houseplant, Epipremnum aureum, pothos ivy, and that the resulting genetically modified plant has sufficient detoxifying activity against benzene and chloroform to suggest that biofilters using transgenic plants could remove VOCs from home air at useful rates.
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Greatly Enhanced Removal of Volatile Organic Carcinogens by a
Genetically Modied Houseplant, Pothos Ivy (Epipremnum aureum)
Expressing the Mammalian Cytochrome P450 2e1 Gene
Long Zhang, Ryan Routsong, and Stuart E. Strand*
Department of Civil and Environmental Engineering, University of Washington, Box 355014, Seattle, Washington 98195-5014,
United States
SSupporting Information
ABSTRACT: The indoor air in urban homes of developed countries is usually
contaminated with signicant levels of volatile organic carcinogens (VOCs), such
as formaldehyde, benzene, and chloroform. There is a need for a practical,
sustainable technology for the removal of VOCs in homes. Here we show that a
detoxifying transgene, mammalian cytochrome P450 2e1 can be expressed in a
houseplant, Epipremnum aureum, pothos ivy, and that the resulting genetically
modied plant has sucient detoxifying activity against benzene and chloroform
to suggest that biolters using transgenic plants could remove VOCs from home
air at useful rates.
Household air is more polluted than oce air and school air,
and those who spend much of their time at home, such as
children and home workers,
receive a proportionately higher
dose of home air carcinogens
than the general population.
Infants are particularly susceptible to indoor air pollution due
to their low body weight and continuous exposure to indoor
air. Loh et al.
ranked the cancer risks of indoor air volatile
organic carcinogens (VOCs). The highest risk VOCs were
benzene, formaldehyde, 1,3-butadiene, carbon tetrachloride,
acetaldehyde, 1,4-dichlorobenzene (PDCB), naphthalene,
perchloroethylene, chloroform, and ethylene dichloride.
VOCs that exceeded acute exposure standards were acrolein
and formaldehyde (during cooking)
and chloroform (during
Some sources of these chemicals can be eliminated or
reduced. For example, PDCB could be greatly reduced by
eliminating products containing it from the home. Form-
aldehyde in household air can be reduced by changing
construction and upholstery material compositions, but
formaldehyde is also emitted from other sources, including
which are not easily eliminated. Other carcinogens
with multiple sources are more dicult to eliminate, such as
benzene, which originates from fuel storage in attached
garages, outside air, and environmental tobacco smoke.
Physical-chemical methods for VOC removal include
adsorption on activated carbon, activated alumina, zeolites or
other surfaces and photocatalytic oxidation.
methods are not well suited for formaldehyde and other
polar compounds. Low molecular weight compounds may be
desorbed in competition with higher molecular weight
pollutants. Adsorption methods are not destructive, and the
sorbents must be periodically regenerated, usually remotely
using energy intensive methods. Low temperature in-place
methods achieved energy ecient regeneration but would
require exterior ducting.
Oxidation methods use photo-
catalysized redox destruction of VOCs on catalytic materials,
such as TiO2. Photocatalytic oxidation methods result in
complete mineralization of most pollutants, but they are
ineective with chlorinated VOCs such as chloroform. Further,
photocatalytic oxidation methods may introduce ozone into
the home air, and they are energy intensive.
Indoor plants have been widely touted as having the ability
to remove air pollutants from indoor air. This approach is
known as the green liverconcept and is a central idea of the
eld of phytoremediation, the use of plants to remove
xenobiotic pollutants from the environment.
Early studies of
air detoxication by household plants found that formaldehyde
was removed from the air of chambers containing spider
Other researchers reported that soil or water alone
could explain the removal.
Subsequently, controlled pure
culture plant experiments showed that plants can assimilate
and metabolize formaldehyde from the air.
However, the
formaldehyde uptake rate through the leaf surface of typical
house plants appears to be insucient to remove formaldehyde
Received: August 27, 2018
Revised: November 3, 2018
Accepted: November 26, 2018
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© XXXX American Chemical Society ADOI: 10.1021/acs.est.8b04811
Environ. Sci. Technol. XXXX, XXX, XXXXXX
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from a typical room without an excessive number of plants.
Several studies have found that common plants can remove
VOCs such as formaldehyde and benzene from air, but those
studies produced highly variable estimates of the rate that a
particular plant species removes a given pollutant from air. The
concentrations used in these tests were several orders of
magnitude greater that those typical of home air (e.g., 17μg
For example, ve dierent laboratories found that
seven plant species removed benzene from the air at rates that
varied by 7 orders of magnitude for the same plants.
These conicting data notwithstanding, plants do have many
attractive features as a platform for metabolism of organic
pollutants. Unlike most bacteria, cultivated plants have excess
energy available to support cometabolic catalysis. Plants have
high surface areas that facilitate mass transfer of trace gases
from the air. Plants are self-sustaining and do not require the
high maintenance typical of bacterial systems. There is
certainty of the genetic and enzymatic composition of the
cultivated plant compared to a soil bacterial community.
The mammalian cytochrome P450 2E1 (2E1) oxidizes a
wide range of important VOCs found in home air, such as
benzene, chloroform, trichloroethylene, and carbon tetra-
The CYP2e1 (2e1) gene has been introduced into
several plants, including trees, resulting in signicantly
increased degradation of the VOCs.
Plants have been genetically modied to overexpress native
plant formaldehyde dehydrogenase activity, but the rate of
formaldehyde removal was increased by only 25% over
unmodied plants.
Expression in transformed tobacco plants
of the transgene for formaldehyde dehydrogenase, faldh, from
Brevibacillus brevis increased formaldehyde removal by 3-fold.
But, to date, no detoxifying genes have been expressed in
Thus, our objective in this study was to increase the
detoxication of indoor air by adding the ability to metabolize
VOCs to a common houseplant by transgene modication.
Our approach was to introduce the mammalian cytochrome
P450 2e1 gene into the common houseplant, pothos ivy
(Epipremnum aureum). Pothos ivy has several advantages over
other houseplants for this purpose: it is robust and grows well
in low light and a method for the transformation of pothos ivy
has been published.
Pothos ivy does not ower in indoor
cultivation or outdoors in the U.S., which is an advantage for
biosafety considerations regarding the release of the transgenes
into the environment. In order to provide additional biosafety
assurances, we added egfp, the gene for the enhanced green
uorescent protein,
EGFP, to the cassette of genes used to
transform the plant.
Preparation of Pothos Ivy. Golden pothos ivy plants,
obtained from a retail horticulture store, were grown under 50
2s1illumination with a 16 h day/8 h night cycle at 25
°C in a plant room. The stem fragments were excised, surface-
sterilized with 15% sodium hypochlorite and then washed with
sterile deionized water three times. The sterilized stem
fragments were cultured on solid Murashige and Skoogs
(MS) basic medium
in culture vessels. After 12 months
culture under light, new leaves and roots developed from stems
and these sterile plants were used for infection with engineered
agrobacteria for genetic modication.
Vector Construction and Genetic Transformation. In
order to genetically modify pothos ivy we constructed a genetic
vector containing the transgenes 2e1, egfp, and hpt, each
anked by promoter and terminator sequences suitable for
pothos ivy. The hpt gene coded for hygromycin B
phosphotransferase, which confers resistance to hygromycin.
Hygromycin was used to select for transformed cells since it
kills wild-type pothos. These three genes were integrated into a
transformation vector (binary vector) based on a system of
cloning vectors called pSAT containing insertion sites for use
with specic restriction enzymes.
Then the binary vector was
introduced into the modied Agrobacterium strain EHA105,
which was used to infect pothos ivy callus cultures.
The rabbit cytochrome P450 2e1 gene was amplied by
polymerase chain reaction (PCR) from the plasmid pSLD50
6 (the sequences of the primers are listed in Supporting
Information (SI) Table S1), a kind gift from S. L. Doty
(University of Washington) and double digested with
restriction enzymes Hind III and KpnI. Then 2e1 DNA was
inserted into cloning vector pNSAT3a to produce pNSAT3a-
2E1. After insertion into pNSAT3a, the 2e1 gene was
integrated between promoter and terminator sequence to
produce an expression cassette to drive the expression of 2e1 in
plant cells. The egfp gene was cloned by PCR from vector
and inserted into pNSAT6a as a Hind III-PstI
fragment to produce pNSAT6a-EGFP. The expression
cassettes of hpt, 2e1,andegfp genes were cut from
pNSAT3a-2E1, and pNSAT6a-EGFP vec-
tors using restriction enzymes Asc I, I-Ppo I, and PI-Psp I
separately and inserted into the pRCS2 binary vector to
produce pRCS22E1-EGFP.
The binary vector pRCS22E1-EGFP was transferred into
Agrobacterium strain EHA105 by the freezethaw method
and the resulting strain, EHA105 (pRCS22E1-EGFP) was
grown in LB medium (lysogeny broth) with 50 mg L1
rifampicin, 100 mg L1spectinomycin, and 300 mg L1
streptomycin for infection of pothos ivy. EHA105 (pRCS2
2E1-EGFP) was initiated in 100 mL LB medium with
rifampicin at 50 mg L1, spectinomycin at 100 mg L1and
cultured overnight at 28 °C on a rotary shaker at 200 rpm. The
bacteria were centrifuged at 4000 rpm for 10 min and
resuspended in liquid E medium (MS medium with 2 mg L1
thidiazuron (TDZ) and 0.2 mg L11-naphthaleneacetic acid
(NAA)) with 100 μM acetosyringone (AS) and cultured under
the same conditions until OD600 (absorbance of bacteria
suspension at 600 nm) of 0.81.0 was reached.
The following method for transformation of pothos ivy was
adapted from that of Zhao et al.
Leaf discs and petiole
segments from sterile pothos plants were immersed in the
agrobacterium culture at 25 °C for 20 min and then transferred
to double-layered lter paper moistened with liquid E medium
with AS at 100 μM in Petri dish for 5-day coculture at 25 °C.
The leaf discs and petiole fragments were washed with sterile
water and transferred to E medium with 100 mg L1
cefotaxime, 100 mg L1carbenicillin (PhytoTechnology
Laboratories) and 20 mg L1hygromycin for screening. The
explants were subcultured to fresh selection medium every 3
After 23 months selection, the somatic embryos that
developed from explants on selection medium were transferred
to fresh medium for another month and then transferred to G
medium (MS medium with 2 mg L16-benzylaminopurine (6-
BA) and 0.2 mg L1NAA) with 100 mg L1cefotaxime, 100
mg L1carbenicillin and 20 mg L1hygromycin and cultured
under light for regeneration. After culture for two months, the
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regenerated plantlets were transferred to MS medium with 100
mg L1cefotaxime, 100 mg L1carbenicillin and 20 mg L1
hygromycin for rooting and growth, which required two
additional months of culture.
Molecular Analysis of Transformed Plants. For
polymerase chain reaction (PCR) analysis, the DNeasy plant
mini kit (Qiagen, Valencia, CA) was used to purify DNA from
hygromycin-resistant plants. PCR reactions were carried out
with primers specicto2e1 and egfp cassettes (SI Table S1).
Total RNA was extracted from the leaves of plants using the
RNeasy plant mini kit (Qiagen, Valencia, CA). For real-time
quantitative RT-PCR analysis, 1 μg of total RNA was reverse
transcribed to cDNA using M-MLV reverse transcriptase
(Promega, Madison, WI). Real-time quantitative PCR was
performed using the SensiFAST SYBR No-ROX kit (Bioline)
on a uorometric thermal cycler, Light Cycler (Roche), and
data were analyzed with Light Cycler 3 software (Roche). The
standard curve was constructed from the plasmid DNA of
pRCS2-2E1-EGFP. The values of transcripts measured using
Figure 1. Structure of binary vector pRCS22E1-EGFP used to transform pothos ivy. T35s, terminator of CaMV 35s gene; hpt, hygromycin
phosphotransferase gene, provides hygromycin resistance; OsActin, promoter of actin gene of Oryza sativa; Tmas, terminator of mannopine
synthase gene; 2e1, cytochrome P450 2E1 gene from rabbit; ZmUbi, promoter of ubiquitin of Zea mays;PvUbi, promoter of ubiquitin gene of
Panicum virgatum (switchgrass); egfp, enhanced green uorescent protein; Trbc, terminator of rubisco small subunit gene; LB, left border of T-
DNA region; RB, right border of T-DNA region.
Figure 2. Genetic transformation of pothos ivy with 2e1 gene via Agrobacterium infection. Leaf discs and fragments of petiole of pothos ivy were
infected with EHA105 harboring pRCS22E1-EGFP. The explants were cultured on somatic embryo induction medium with hygromycin at 20 mg
L1for selection. (A) Callus developed from explants after 34 months screening. (B) Hygromycin resistant callus was transferred to regeneration
medium supplied with hygromycin at 20 mg L1for 24 months to induce development of new plantlets. (C) Regenerated plants were transferred
to MS medium with hygromycin at 20 mg L1for rooting and growth. (D) PCR- and RT-PCR-positive transformed plants were cultured on callus
induction medium with hygromycin for callus induction and propagation.
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RT-qPCR were normalized to the pothos ivy 5.8S gene and
presented relative to the level of the transcript in clone VD1.
Benzene and Chloroform Uptake by Transformed
Pothos Ivy. Sterile plantlets of pothos ivy clones (1 g) were
incubated in 40 mL volatile organic analysis (VOA) vials
(Fisher Scientic, 14823-213), closed with septum valves
(Mininert, Valco Instruments Co. Inc., 614163), and
containing 5 mL half-strength Hoaglands solution (Caisson
Laboratories, HOP0110LT.1). Wild-type untransformed
plantlets and no-plant controls were incubated in parallel
with clone VD3 and each treatment was repeated in
Benzene gas was injected into the vials using gastight glass
syringes to achieve a headspace concentration of 1850 ±160
mg m3, taking into account gas liquid partitioning by Henrys
Law. The vials were incubated for 9 days with rotary shaking at
80 rpm. The concentration of benzene was determined by
manually injecting 100 μL of the headspace into a GCFID
(ame ionization detector) (PerkinElmer AutoSystem XL).
Chromatographic parameters were: oven temperature 60 °C,
injector temperature 250 °C, and detector temperature 250
°C, 1.33 mL min1nitrogen carrier gas, using a ResTek RTX-1
microcapillary column (ResTek, 10121).
Similarly, chloroform was introduced into VOA vials using
gastight glass syringes from sealed aqueous dilutions of
chloroform (Acros Organics, 423550010). Transformed
plantlets, wild type (WT), and no plant controls were
incubated in quadruplicate, and headspace samples taken for
analysis of chloroform levels by gas chromatography with an
electron capture detector (GCECD) (PerkinElmer AutoSys-
tem XL) with a VOCOL capillary column 60 m ×0.53 mm
(Sigma). Chromatographic parameters were detector temper-
ature at 325 °C, nitrogen carrier gas at 1.76 mL min1, with a
100 mL min1split, the oven at 100 °C, and the injection port
at 300 °C.
EGFP Fluorescence. The EGFP signal of epidermal cells
of pothos leaf was observed by uorescent microscopy using
the LSM 5 PASCAL system (ZEISS). The EGFP signal was
excited by blue light and a FITI lter was used to collect
uorescent light. Axiocam 503 mono camera and software
ZEN 2.3 lite were used to capture pictures.
Data Analysis. Data were analyzed for statistical
signicance using ANOVA in Microsoft Excel software
(Microsoft Excel 2016 MSO). When ANOVA analysis gave a
signicant dierence, Fishers Least Signicant Dierence
Groupings diering by statistical signicance (p< 0.05) are
labeled by letters in the gures.
Vector Construction and Generation of Transgenic
Pothos Ivy. The structure of the plasmid pRCS22E1-EGFP
used to transform pothos ivy is shown in Figure 1. In order to
achieve constant, high levels of expression, all of the transgenes
were driven by constitutive monocot promoters. The
hygromycin resistance gene, hpt, was driven by the actin
promoter from rice (Oryza sativa),
the 2e1 gene was driven
by the ubiquitin promoter of corn (Zea mays),
and the egfp
gene was driven by the ubiquitin promoter from switchgrass
(Panicum virgatum).
The explants of pothos ivy were infected with EHA105
containing the vector pRCS22E1-EGFP and then screened
on callus induction medium with hygromycin as selection
agent for 23 months. Capitate somatic embryos developed
from cut edges of leaf discs and petiole fragments (Figure 2A).
During subsequent culture, calli formed at the base and more
cluster somatic embryos developed from the calli. After 34
months culture, the hygromycin-resistant calli were transferred
to regeneration medium for induction of plantlets. After
another 23 months culture, plantlets developed with both
shoots and roots from the somatic embryos. Some plantlets
developed only with shoots (Figure 2B). These plants were
transferred to MS medium with hygromycin for further growth
and rooting (Figure 2C). The leaf discs of PCR and RT-qPCR
positive lines were cultured on E medium with 15 mg L1
hygromycin to induce somatic embryos for propagation while
still under selection (Figure 2D).
Molecular Analysis to Conrm the Transformation of
Hygromycin-Resistant Lines. PCR primed by primer pairs
annealing to promoter and terminator regions of 2e1 and egfp
cassettes conrmed the integration of target genes into the
genome of pothos ivy (data not shown). To measure the
transcript abundance of 2e1 and egfp genes RT-qPCR was
performed for eight transgenic lines, VD1-VD8. The
expression levels of egfp were lower than that of 2e1, and
were separated into two groups, with signicant dierences
between VD3 and VD2 or VD7 (p< 0.01, Figure 3). The
expression levels of the 2e1 gene between dierent transformed
lines were dierent with high signicance (p = 0.00001). The
clonal lines VD3, VD7, and VD8 had much higher expression
levels of 2e1 compared to other lines. None of the transformed
clonal lines had observable changes in morphology or growth
compared to wild types.
Figure 3. Transcript abundance measured using quantitative RT-PCR
on pothos ivy lines transformed with 2e1 and egfp genes. The y-axis
shows values that were normalized to the pothos ivy 5.8s rRNA gene
and relative to the level of VD1 (n=3±SE). Letters indicate means
that were not signicantly dierent (p= 0.05, ANOVA).
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EGFP Observation. Using a uorescent microscope, EGFP
uorescence was observed near the plasma membrane and
around the nucleus (Figure 4A) due to the presence of
vacuoles in the epidermal cells of pothos ivy leaf. The
emissions were marginally greater than emissions from the wild
type, but weak. The wild-type cells were weakly autouor-
escent generally, but not specically from the cytosol. Green
uorescence was not visible to the eye in the transformed
pothos ivy with hand-held UV lamp illumination.
Benzene Uptake by Transformed Pothos Ivy. To
determine the ability of 2e1-egfp transformed pothos ivy to
take up benzene, we incubated plants in closed vials with the
VOC. Benzene (144 μg) was injected into 40 mL VOA vials
containing transformed and wild-type pothos ivy to achieve a
nal headspace concentration of 2500 mg m3benzene. After 3
days culture, the benzene concentration in vials with VD3
plants had fallen dramatically (Figure 5). After 8 days, the
benzene concentration in no-plant vials had fallen by about
10%. The benzene concentrations in the vials containing VD3
plants were signicantly dierent compared to vials containing
wild-type plants after 3 days culture (p= 0.039), p= 0.012 at
day 4, and p= 0.0008 at day 8.
The time course of the benzene concentration in the vials
with transformed pothos ivy clone VD3 was plotted on
semilogarithmic axes and t by linear regression with a rst-
order rate constant equal to (0.249 d1,SI Figure S1), or
0.115 d1(g fresh biomass)1(SI Table S2). Since small
pothos plants have 29 cm2leaf area (g fresh biomass)1, this
kinetic constant is equivalent to 39.8 d1(m2leaf area)1,
normalized to leaf area. The slope of the best linear t to the
semilogarithmic plot of the time course of benzene
concentration for wild-type plants (0.044 d1,SI Figure
S2)wassignicantly dierent from zero (p= 0.015),
suggesting that the wild-type plants did take up some benzene.
The wild-type pothos took up benzene at a rst-order rate
normalized to biomass equivalent to- 0.024 d1(g biomass)1,
or 8.5 d1(m2leaf area)1, normalized to leaf area. The
normalized rate constant for uptake of benzene uptake by
transformed clone VD3 was 4.7 times that of the wild-type.
Chloroform Uptake by Transformed Pothos Ivy. The
concentration of chloroform in the headspace of vials
incubated with VD3 plants fell rapidly, while chloroform
concentrations in incubations with wild-type plantlets and no-
plant controls did not change signicantly (Figure 6). The
concentration of chloroform decreased by 82% during the rst
3 days in the vials containing clone VD3 plants and chloroform
was barely detectable after 6 days. Linear regression of the
semilogarithmic plot of the chloroform data yielded a rst-
order degradation constant equal to 0.549 d1(SI Figure
S3). The slope of the best linear t to the semilogarithmic plot
of the time course of chloroform concentration for wild-type
plants (SI Figure S4) was not signicantly dierent from zero
(p= 0.22), suggesting that the wild-type plants did not take up
chloroform. The rate constant for the VD3 transformed pothos
ivy normalized to biomass was 0.552 d1(g fresh biomass)1,
equivalent to 180 d1(m2leaf area)1, normalized to leaf area
(SI Table S3).
Figure 4. Observation of EGFP signal in the epidermal cells of pothos ivy clone VD3 using uorescence microscopy. The green uorescence signal
of EGFP was observed in cytosol in the epidermal cells of leaf of pothos ivy clone VD3 (A). The emissions in the wild-type pothos ivy (B) were due
to autouorescence.
Figure 5. Uptake of benzene by 2e1-egfp transformed pothos ivy
grown in liquid culture. The concentration of benzene in headspace
during eight-day culture of VD3 (2e1), wild-type plants (WT), and
no-plant controls (NPC). N= 4. Averages ±SE.
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DOI: 10.1021/acs.est.8b04811
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VOCs in indoor air pose signicant cancer risks to vulnerable
populations, such as children, yet there are no practical,
sustainable technologies available for their removal in the
home. Physical-chemical methods based on sorbents and
oxidation methods are energy intensive and of limited use for
the removal of formaldehyde and chloroform, respectively.
Various houseplants have been touted as having the ability to
remove VOCs from air, but plant uptake rates vary
exponentially from one study to another. Many studies appear
to be aected by artifactual enhancement of soil bacterial
activities by high VOC concentrations.
In this study we also
used high VOC concentrations to facilitate analysis by hand
injection of headspace samples onto GCFID in the case of
benzene, but we performed the assays in axenic conditions,
without bacterial activity. As can be seen in Figures 5 and 6
there was little or no loss of benzene or chloroform in the vials
containing wild-type pothos ivy, while most of the benzene and
all of the chloroform was removed in 6 days in the vials with
2E1-expressing clone VD3. These results show the eective-
ness of genetically modied pothos for VOC removal
compared to wild-type pothos.
As we have shown for 2e1-transformed tobacco, other VOC
substrates of 2E1 may also be removed by the transformed
Future work will determine whether other indoor air
pollutants that are known to be substrates of 2E1 in
mammalian cultures, such as PDCB, toluene, naphthalene,
and methyl chloroform, are removed by 2e1-transformed
Expression of green uorescent protein was intended as a
visible indication that the pothos ivy was transformed, but
uorescence of transformed clone VD3 was too weak to be
visible without microscopy. Other variants of GFP, such as
and the use of a stronger monocot promoter may
provide stronger uorescence.
Additional improvements for removal of VOCs from home
air using transgenic houseplants could be made by combining
expression of 2e1 with other detoxifying genes. Formaldehyde,
the other VOC that poses most risk in home air will be of
prime interest. Overexpression of faldh gene from Brevibacillus
brevis in tobacco conferred plants a high tolerance to HCHO
and increased the ability to take up formaldehyde 23 times
faster than wild-type plants.
The faldh gene could be stacked
with 2e1 and other detoxifying genes in vectors that are used to
genetically modify pothos ivy and other houseplants, resulting
in plants that could degrade most of the important indoor air
Since 2e1 gene expression in the transformed pothos ivy is
under constitutive promoters the level of 2E1 expression is
expected to be independent of benzene or chloroform
concentration. Therefore, the kinetic parameters of pollutant
degradation are expected to be invariant with pollutant
concentration. However, we have not conrmed this
assumption empirically.
We calculated the performance of an enclosed, forced-air
biolter (see SI) using the same rst-order degradation
constant observed in the batch experiments with chloroform,
0.52 d1(g biomass)1. For the case of a completely mixed
biolter with a volume of 0.7 m3and an airow rate of 300 m3
h1, 10 kg of pothos ivy clone VD3 could remove 34% of the
chloroform in one pass. This hypothetical biolter would have
a clean air delivery rate (CADR) of 100 m3h1, comparable to
CADRs of current commercial home particulate lters.
calculation, while tentative, suggests that genetically modied
plants may have practical utility for sustainable phytoremedia-
tion of home air.
Compared to current chemical/physical methods for
removal of VOCs from indoor air biolters using transgenic
plants oer the advantages of low energy use and decreased
need for maintenance. All of the removal methods require a
means for moving the air through the apparatus, but adsorptive
methods also require signicant energy expenditure to
regenerate the media and photooxidative methods require
high energy inputs to oxidize the pollutants, making those
methods less sustainable. Transgenic phytoremediation
requires very little additional energy beyond that required for
air movement. Pothos ivy is well adapted to medium- and low-
light levels so articial lighting would usually not be required,
giving phytoremediation an intrinsic sustainability advantage.
More work is needed to conrm these ndings and to
establish the practical usefulness of transgenic biolters. It is
necessary to determine the removal rates at low concentrations
of indoor air pollutants, the eectiveness of the formaldehyde
dehydrogenase gene expressed in pothos, the eects of light
and dark and photoperiod on removal, the eects of increased
mixing and air ow rate in the biolter, and whether increased
VOC removal eciencies can be achieved through biological
manipulations such as increased transgene copy numbers.
SSupporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.est.8b04811.
The biolter model, four gures and three tables (PDF)
Corresponding Author
*Phone: 206-543-5350; fax: 206-685-9996; e-mail: sstrand@
Stuart E. Strand: 0000-0002-6700-3498
The authors declare no competing nancial interest.
Figure 6. Uptake of chloroform by 2e1-egfptransformed pothos ivy
grown in liquid culture. The concentration of chloroform in
headspace during 11-day culture of VD3, wild-type plants (WT),
and no-plant controls (NPC). N=4±SE.
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DOI: 10.1021/acs.est.8b04811
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This work was funded by NSF CBET-1438266, Amazon
Catalyst grant UW 100631088, and NIEHS grant 2P42-
(1) Jenkins, P. L.; Phillips, T. J.; Mulberg, E. J.; Hui, S. P. Activity
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Environmental Science & Technology Article
DOI: 10.1021/acs.est.8b04811
Environ. Sci. Technol. XXXX, XXX, XXXXXX
... This new level of understanding may lead to the development of transgenic and hybrid plants with improved tolerance to xenobiotics, extraction capabilities, growth rate, root depth, and other favorable characteristics for remediation. For example, the expression of the mammalian Cytochrome P450 2E1, a gene involved in the metabolism of xenobiotics in the liver, has been expressed in numerous genetically engineered plants, drastically increasing the plants ability to degrade xenobiotic compounds such as carcinogenic VOCs (Doty et al. 2007(Doty et al. , 2000James et al. 2008;Legault et al. 2017;Zhang et al. 2019). Plants use pathways and enzymes similar to livers in mammalian systems; however, plants lack enzymes capable of mineralizing organic compounds due to the fact that plants do not utilize organic compounds for their energy and Content courtesy of Springer Nature, terms of use apply. ...
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Background: Understanding the interaction between organisms and the environment is important for predicting and mitigating the effects of global phenomena such as climate change, and the fate, transport, and health effects of anthropogenic pollutants. By understanding organism and ecosystem responses to environmental stressors at the molecular level, mechanisms of toxicity and adaptation can be determined. This information has important implications in human and environmental health, engineering biotechnologies, and understanding the interaction between anthropogenic induced changes and the biosphere. One class of molecules with unique promise for environmental science are lipids; lipids are highly abundant and ubiquitous across nearly all organisms, and lipid profiles often change drastically in response to external stimuli. These changes allow organisms to maintain essential biological functions, for example, membrane fluidity, as they adapt to a changing climate and chemical environment. Lipidomics can help scientists understand the historical and present biofeedback processes in climate change and the biogeochemical processes affecting nutrient cycles. Lipids can also be used to understand how ecosystems respond to historical environmental changes with lipid signatures dating back to hundreds of millions of years, which can help predict similar changes in the future. In addition, lipids are direct targets of environmental stressors, for example, lipids are easily prone to oxidative damage, which occurs during exposure to most toxins. Aim of review: This is the first review to summarize the current efforts to comprehensively measure lipids to better understand the interaction between organisms and their environment. This review focuses on lipidomic applications in the arenas of environmental toxicology and exposure assessment, xenobiotic exposures and health (e.g., obesity), global climate change, and nutrient cycles. Moreover, this review summarizes the use of and the potential for lipidomics in engineering biotechnologies for the remediation of persistent compounds and biofuel production. Key scientific concept: With the preservation of certain lipids across millions of years and our ever-increasing understanding of their diverse biological roles, lipidomic-based approaches provide a unique utility to increase our understanding of the contemporary and historical interactions between organisms, ecosystems, and anthropogenically-induced environmental changes.
... In general, the average air quality improvement (only accounting for the major air pollutants: O 3 , PM 10 , NO 2 , SO 2 , and CO) due to plants is estimated to be relatively low at around 1% (Nowak et al., 2006). However, the ease by which microbial genomes and plant microbiomes may be manipulated (Zhang et al., 2019), and the capacities for pollutant removal of these complex matrices demonstrated in the laboratory, indicates that the plantÀmicroorganism system is a promising tool for the management of air quality in the future (Doty et al., 2007). ...
... Findings from a recent study undertaken by Zhang et al. 119 indicate that genetic modification may enable the selection and enhancement of micromorphological features for air pollution removal, as previously suggested by Lawson and Blatt 116 . Due to their complex leaf surface micromorphology, broadleaf species are more effective for deposition than coniferous species per leaf area, whereas coniferous species are more effective at tree scale due to a larger total leaf area 110,115 . ...
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Vegetation can form a barrier between traffic emissions and adjacent areas, but the optimal configuration and plant composition of such green infrastructure (GI) are currently unclear. We examined the literature on aspects of GI that influence ambient air quality, with a particular focus on vegetation barriers in open-road environments. Findings were critically evaluated in order to identify principles for effective barrier design, and recommendations regarding plant selection were established with reference to relevant spatial scales. As an initial investigation into viable species for UK urban GI, we compiled data on 12 influential traits for 61 tree species, and created a supplementary plant selection framework. We found that if the scale of the intervention, the context and conditions of the site and the target air pollutant type are appreciated, the selection of plants that exhibit certain biophysical traits can enhance air pollution mitigation. For super-micrometre particles, advantageous leaf micromorphological traits include the presence of trichomes and ridges or grooves. Stomatal characteristics are more significant for sub-micrometre particle and gaseous pollutant uptake, although we found a comparative dearth of studies into such pollutants. Generally advantageous macromorphological traits include small leaf size and high leaf complexity, but optimal vegetation height, form and density depend on planting configuration with respect to the immediate physical environment. Biogenic volatile organic compound and pollen emissions can be minimised by appropriate species selection, although their significance varies with scale and context. While this review assembled evidence-based recommendations for practitioners, several important areas for future research were identified.
The environmental challenges of climate change increase the energy usage and peak demands of buildings. Most extant studies of greenery systems focus on exterior applications such as green façades and roofs, which indirectly affect the indoor environment. Few studies have focused on quantifying the influence of indoor greenery systems on building energy consumption. The cooling effects of indoor greenery systems such as living walls are largely accounted for by the evapotranspiration (ET) process, in which water is transferred to the ambient environment through the evaporation from and transpiration of plants. Current building energy simulation software such as EnergyPlus did not have a module for modeling indoor greenery systems. In this study, an ET model was created using a machine learning algorithm—Gaussian Mixture Regression (GMR) based on experimental data. An indoor living wall model quantifying sensible and latent loads from the ET process was integrated with the energy simulation software—EnergyPlus through the Python plugin feature. The U.S. Department of Energy (DOE) medium-sized office building reference model was modified and used in this study to evaluate indoor living walls’ impacts on cooling energy use. A parametric study on leaf to floor area ratios (LFAR), orientations, distances from windows, and climates was conducted to evaluate the influence of each factor on indoor living walls’ performance. Cooling effects of indoor living walls were evaluated in three ASHRAE climates with high cooling demands. Observable cooling energy savings were obtained for the south, east, and west perimeter zones while savings for the north perimeter zone was negligible in all three climates. With the consideration of extra electricity use from direct expansion (DX) dehumidification devices for humidity control, the maximum cooling electricity savings in Los Angeles, CA are 25.1% when LFAR=1.5 for the south perimeter zone, 14.4% when LFAR=0.5 for the east perimeter zone, 0.3% when LFAR=0.3 for the north perimeter zone, and 14.5% when LFAR=0.5 for the west perimeter zone on the design day.
Biotechnology has changed the debate about the criteria used to determine the acceptability of any agricultural technology by introducing new questions: Do we need it? Should we do it? The debate continues. Several arguments in favor of agricultural biotechnology are presented, and the crops and countries using it are shown in this chapter. The concept of substantial equivalence is presented. Adoption of the technology has been very rapid, but it has not led to widespread societal approval.
Ornamental plants are primarily decorative and, as such, are purchased and appreciated according to their visual characteristics. But beyond this, the other senses may be concerned. This multisensoriality justifies the use of sensory methodologies to study their characteristics and understand the perception of consumers, their expectations, and their behaviors. Some studies have shown the value of sensory evaluation in enhancing sensory properties. Other studies have identified drivers of liking and weighting between intrinsic and extrinsic variables, with a particular focus on liking, preference, and purchase intent or identification of plant uses. These studies used several techniques such as eye tracking, central location test (CLT), or home-use test (HUT). But before carrying out evaluations, methodologies must be adapted to the particularities of ornamental plants: variability, size, evolution over time, etc. These adaptations concern the management of this variability, the use of visual support or the presentation of real plants, the evaluation in control location test or at home, and some questions relating to consumers to be questioned.
The cytochrome P450 2E1 (CYP2E1) enzyme encoded by CYP2E1 plays an important role in the metabolism of organic compounds in mammalian liver cells. In this study, the plasmid pCAMBIA2300 harboring the rabbit CYP2E1 was transferred into Agrobacterium tumefaciens; this was then transferred into internodes of Ardisia pusilla. Shoot primordia, whose appearance resembles that of the in vitro protocorm-like body of orchids, regenerated from 121 of 332 internodes that were cultured in selection medium supplemented with 5 mg·L−1 kanamycin. PCR analysis confirmed that 25 of 89 putative transgenic plants (28.0%) stably harbored the CYP2E1 and NPTII genes, and Southern blot analysis revealed the presence of one to three copies of CYP2E1 within the genome of the 25 transgenic plants. The mRNA expression of the transgene was confirmed in 12 of 25 CYP2E1-transgenic plants by Northern blot analysis. Western blot analysis indicated the presence of a 53-kDa recombinant rabbit CYP2E1 protein in the 12 CYP2E1-transgenic A. pusilla plants. The aniline 4-hydroxylase activity of rabbit CYP2E1 in nine CYP2E1-transgenic A. pusilla plants was higher than that in non-transgenic A. pusilla plants. There was a statistically significant increase (5.1–6.1-fold) in the toluene removal ability of the transgenic line CYP2E1-2–2 compared to that observed in wild-type Ardisia plants at different times after exogenous toluene exposure.
Phytoremediation is a sustainable remedial approach for removing benzene from environment. Plant associated bacteria could ameliorate the phytotoxic effects of benzene on plant, although the specificity of these interactions is unclear. Here, we used proteomics approach to gain a better understanding of the mechanisms involved in plant-bacteria interactions. Plant associated bacteria was isolated and subsequently inoculated into the sterilized Helianthus annuus, and the uptake rates of benzene by these inoculated plants were evaluated. At the end of the experiment, leaves and roots proteins were analyzed. The results showed inoculated H. annuus with strain EnL3 removed more benzene than other treatments after 96 hr. EnL3 was identified as Enterobacter sp. according to 16S rDNA analysis. Based on the comparison of proteins, 62 proteins were significantly up or down regulated in inoculated leaves, while 35 proteins were significantly up or down regulated in inoculated roots. Furthermore, there were 4 and 3 identified proteins presented only in inoculated H. annuus leaves and roots, respectively. These proteins involved in several functions including transcription and translation, photosynthesis, and stress response. The network among anti-oxidant defense system, protein synthesis, and photosynthetic electron transfer are involved in collaboratively activate the benzene uptake and stress tolerance in plant.
The development and subsequent incorporation of the advanced materials and technologies in buildings, with a view to target energy savings, and to fulfill the energy requirements have been gaining impetus during the recent years. The inherent vision lying behind the state-of-the-art technological advancements taking place in the construction sector is to sustain the energy efficiency in both existing and newly developed buildings on a long run. Thermal energy storage (TES), achieved through the phase-change materials (PCMs), is one among a few energy-efficient technologies available. The energy demand at the end-user side can be greatly satisfied using the TES technologies. Using bio-based PCMs in buildings is considered to be an ever-growing as well as an emerging field of interest to wider scientific and engineering communities, worldwide. This chapter is devoted to provide an in-depth understanding of a variety of bio-based PCMs for accomplishing thermal storage and energy efficiency in buildings. The nucleus of this chapter is focused on the TES properties enhancement for a variety of bio-based PCMs through the incorporation of different functional materials thereby; energy efficiency in buildings can be achieved.
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The deposition of toxic munitions compounds, such as hexahydro-1, 3, 5-triniitro-1, 3, 5-trizaine (RDX), on soils around targets in live-fire-training ranges is an important source of groundwater contamination. Plants take up RDX but do not significantly degrade it. Reported here is the transformation of two perennial grass species, switchgrass (Panicum virgatum) and creeping bentgrass (Agrostis stolonifera), with the genes for degradation of RDX. These species possess a number of agronomic traits making them well-equipped for the uptake and removal of RDX from root zone leachates. Transformation vectors were constructed with xplA and xplB, which confer the ability to degrade RDX, and nfsI, which encodes a nitroreductase for the detoxification of the co-contaminating explosive 2, 4, 6-trinitrotoluene (TNT). The vectors were transformed into the grass species using Agrobacterium tumefaciens infection. All transformed grass lines showing high transgene expression levels removed significantly more RDX from hydroponic solutions and retained significantly less RDX in their leaf tissues than wild type plants. Soil columns planted with the best-performing switchgrass line were able to prevent leaching of RDX through a 0.5 m root zone. These plants represent a promising plant biotechnology to sustainably remove RDX from training range soil, thus preventing contamination of groundwater. This article is protected by copyright. All rights reserved.
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The "ASHRAE Position Document on Filtration and Air Cleaning" provides Society members and other stakeholders with information on these technologies and their application. This column answers a few questions about the main positions and statements formulated in the position document (
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Leaf and petiole explants of monocotyledonous pothos (Epipremnum aureum) ‘Jade’ were cultured on Murashige and Skoog basal medium supplemented with N-(2-chloro-4-pyridl)-N′-phenylurea (CPPU) or N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (TDZ) with α-naphthalene acetic acid (NAA). Somatic embryos appeared directly from explants after 4–8 weeks of culture; 9.1 μM TDZ with 1.1 μM NAA induced 61.1 % leaf discs and 94.4 % of petiole segments to produce plantlets through embryo conversion. Using this established regeneration method and an enhanced green fluorescent protein (GFP) gene (egfp) as a reporter marker, an Agrobacterium-mediated transformation procedure was developed. Leaf discs and petiole segments were inoculated with Agrobacterium tumefaciens strain EHA105 harboring a binary vector pLC902 that contains novel bi-directional duplex promoters driving the egfp gene and hygromycin phosphotransferase gene (hpt), respectively. The explants were co-cultivated with strain EHA105 for 3, 5, and 7 days, respectively prior to selective culture with 25 mg l−1 hygromycin. A 5-day co-cultivation led to 100 % of leaf discs to show transient GFP expression and 23.8 % of the discs to produce stable GFP-expressing somatic embryos. A 7-day co-cultivation of petiole explants resulted in the corresponding responses at 100 and 14.3 %, respectively. A total of 237 transgenic plants were obtained, and GFP fluorescence was observed in all plant organs. Regular PCR and quantitative real-time PCR analyses confirmed the presence of 1 or 2 copies of the egfp gene in analyzed plants. The highly efficient regeneration and transformation systems established in this study may enable genetic improvement of this vegetatively propagated species through biotechnological means.
A controlled field study was performed to evaluate the effectiveness of transgenic poplars for phytoremediation in a field setting. Three hydraulically contained test beds were planted with twelve transgenic poplars, twelve wild type (WT) poplars, or left unplanted, and dosed with equivalent amounts of trichloroethylene (TCE). Degradation of TCE was enhanced in the transgenic tree bed, but not to the extent of the enhanced removal observed in laboratory studies. Total chlorinated ethene removal was 87% in the CYP2E1 bed, 85% in the WT bed, and 34% in the unplanted bed in 2012. Evapotranspiration of TCE from transgenic leaves was reduced by 80% and diffusion of TCE from transgenic stems was reduced by 90% compared to WT. Cis-dichloroethene and vinyl chloride levels were reduced in the transgenic tree bed. Chloride ion accumulated in the planted beds corresponding to the TCE loss, suggesting that contaminant dehalogenation was the primary loss fate. Modeling of TCE in the plant indicated that the enhanced rate of metabolism in CYPE1 roots was insufficient to substantially increase uptake of TCE in a field setting.
Removal rates of benzene and formaldehyde gas by houseplants reported by several laboratories varied by several orders of magnitude. We hypothesized that these variations were caused by differential responses of soil microbial populations to the high levels of pollutant used in the studies, and tested responses to benzene by plants and soils separately. Five houseplant species and tobacco were exposed to benzene under hydroponic conditions and the uptake rates compared. Among the test plants, Syngonium podophyllum and Chlorophytum comosum and Epipremnum aureum had the highest benzene removal rates. The effects of benzene addition on populations of soil bacteria were determined using reverse transcription quantitative PCR (RT-qPCR) assays targeting microbial genes involved in benzene degradation. The total bacterial population increased as shown by increases in the levels of eubacteria 16S rRNA, which was significantly higher in the high benzene incubations than in the low benzene incubations. Transcripts (mRNA) of genes encoding phenol monooxygenases, catechol-2,3-dioxygenase and the housekeeping gene rpoB increased in all soils incubated with high benzene concentrations. Therefore the enrichment of soils with benzene gas levels typical of experiments with houseplants in the literature artificially increased the levels of total soil bacterial populations, and especially the levels and activities of benzene-degrading bacteria.
The faldh gene coding for a putative Brevibacillus brevis formaldehyde dehydrogenase (FALDH) was isolated and then transformed into tobacco. A total of three lines of transgenic plants were generated, with each showing 2- to 3-fold higher specific formaldehyde dehydrogenase activities than wild-type tobacco, a result that demonstrates the functional activity of the enzyme in formaldehyde (HCHO) oxidation. Overexpression of faldh in tobacco confers a high tolerance to exogenous HCHO and an increased ability to take up HCHO. A (13)C-nuclear magnetic resonance technique revealed that the transgenic plants were able to oxidize more aqueous HCHO to formate than the wild-type (WT) plants. When treated with gaseous HCHO, the transgenic tobacco exhibited an enhanced ability to transform more HCHO into formate, citrate acid, and malate but less glycine than the WT plants. These results indicate that the increased capacity of the transgenic tobacco to take up, tolerate, and metabolize higher concentrations of HCHO was due to the overexpression of B. brevis FALDH, revealing the essential function of this enzyme in HCHO detoxification. Our results provide a potential genetic engineering strategy for improving the phytoremediation of HCHO pollution.
Uptake, translocation and metabolism of 14C-labelled formaldehyde in the leaves of Epipremnum aureum (Golden Potho) and Ficus benjamina (Weeping Fig) were investigated. Plants were exposed in light and dark to 14C-formaldehyde (500 μg m−3) in gas exposure chambers. The amount of 14C-incorporation into the soluble (water-extractable) and insoluble fractions of leaves, stem sections and roots was determined. The soluble 14C-activity was fractionated by ion exchange chromatography followed by thin-layer chromatography/autoradiography. Approximately 60–70% of the applied 14C-formaldehyde was recovered from the plants. In the light about five times more 14C-formaldehyde was assimilated than in the dark. The amount of 14C-label derived from 14C-formaldehyde, which was incorporated into acid-stable metabolites, was enhanced to an even larger extent in the light. The 14C-activity pattern closely resembled the general labelling spectrum of photosynthates, obtained after a 14CO2 exposure. A substantial amount of labelled material, mostly sucrose, was translocated into the stems and roots. Our results suggest that in the light 14C enters the Calvin cycle after an enzymatic two-step oxidation process of 14C-formaldehyde to 14CO2. The activities of the respective enzymes, formaldehyde dehydrogenase and formate dehydrogenase, were determined. Among 27 ‘leafy’ indoor decorative plants, a screening experiment revealed no outstanding species with regard to its capacity for metabolism of formaldehyde, and rate of uptake through stomata was too low to justify claims that plants contribute usefully to indoor air purification.
A sealed, Plexiglas chamber with temperature and humidity control and illuminated externally with wide spectrum grow lights was used to evaluate the ability of golden pothos (Scindapsus aureus), nephthytis (Syngonium podophyllum), and spider plant (Chlorophytum elatum var.vittatum) to effect the removal of formaldehyde from contaminated air at initial concentrations of 15–37 ppm. Under the conditions of this study, the spider plant proved most efficient by sorbing and/ or effecting the removal of up to 2.27 fig formaldehyde per cm2 leaf surface area in 6 h of exposure. The immediate application of this new botanical air-purification system should be in energy-efficient homes that have a high risk of this organic concentrating in the air, due to outgassing of urea-formaldehyde foam insulation, particleboard, fabrics and various other synthetic materials.