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\begin{document}

\title{Glowing Plants Can Light Up the Night Sky? A Review}



\author[1]{Bolong Li}%
\author[1]{Ru Chen}%
\author[1]{Chenba Zhu}%
\author[1]{Fantao Kong}%
\affil[1]{Dalian University of Technology}%


\vspace{-1em}



  
  \date{June 17, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Luminescence, a physical phenomenon that producing cool light in vivo,
has been found in bacteria, fungi and anminals but not yet in
terrestrial higher plants. Through genetic engineering, it is feasible
to introduce luminescence system into living plant cells as biomarkers.
Recently, some plants transformed with luminescent systems can glimmer
in darkness, which can be observed by our naked eyes and provide a novel
lighting resource. In this review, we summarized the development of
luminescence in plant cells, followed by exampling the successful cases
of glowing plants transformed with diverse luminescent systems. The
potential key factors to optimize a glowing plant are also discussed.
Our review is useful for the creation of the optimized glowing plants,
which can be used not only in scientific research, but also as promising
substitutes of artificial light sources in the future.%
\end{abstract}%



\sloppy


\textbf{Glowing Plants Can Light Up the Night Sky? A Review}

\textbf{Bolong Li\textsuperscript{1},Ru Chen\textsuperscript{1}, Chenba
Zhu\textsuperscript{1, 2}, Fantao Kong\textsuperscript{1,}}
\textsuperscript{*}

\textsuperscript{1} School of Bioengineering, Dalian University of
Technology, Dalian 116024, China

\textsuperscript{2} Institute of Biotechnology, RWTH Aachen University,
Worringerweg 3, 52074 Aachen, Germany

\textsuperscript{*}\textbf{Correspondence:}

Fantao Kong

School of Bioengineering, Dalian University of Technology, Dalian
116024, China

Email: kongfantao@dlut.edu.cn

Tel: +8615642336188; Fax: +86041184708083

\textbf{Funding information:}

National Natural Science Foundation of China,

Grand/Award Number: 31900221;

Natural Science Foundation of Liaoning Province of China,

Grand/Award Number: 2020-MS-102.

\emph{There are no conflicts of interest.}

\textbf{Abstract}

Luminescence, a physical phenomenon that producing cool light \emph{in
vivo,} has been found in bacteria, fungi and anminals but not yet in
terrestrial higher plants. Through genetic engineering, it is feasible
to introduce luminescence system into living plant cells as biomarkers.
Recently, some plants transformed with luminescent systems can glimmer
in darkness, which can be observed by our naked eyes and provide a novel
lighting resource. In this review, we summarized the development of
luminescence in plant cells, followed by exampling the successful cases
of glowing plants transformed with diverse luminescent systems. The
potential key factors to optimize a glowing plant are also discussed.
Our review is useful for the creation of the optimized glowing plants,
which can be used not only in scientific research, but also as promising
substitutes of artificial light sources in the future.

\textbf{Keywords:}

Glowing plant; Luminescence; Genetic engineering; Bioluminescent system;
Fluorescent protein

\textbf{Introduction}

Luminescence is a common physical phenomenon to create light, which was
discovered among more than 10,000 species, i.e., bacteria, fungi,
protists and animals (Desjardin et al., 2008; Haddock et al., 2010;
Meighen, 1991). Luminescence is a kind of specific communication
approaches for signaling, such as alarming predators (Burford \&
Robison, 2020), trapping prey (Verdes \& Gruber, 2017; Wainwright \&
Longo, 2017) and attracting mates (Ellis \& Oakley, 2016). During the
past years, it was found that fluorescent proteins (FPs) and
bioluminescent systems are responsible for induction of most native
luminescence (Kim \& Paulmurugan, 2021). FPs generate photoluminescece
that is excited by specific emission without consumption of ATP
(Chudakov et al. 2010), while bioluminescent systems exhibit light by
oxidation of a specific substrate, luciferin, with co-factors, e.g., ATP
and NADH, and catalyzed by the specific enzyme, luciferase (Fleiss \&
Sarkisyan, 2019).

Despite luminescence was found among many species, native terrestrial
plants haven't been reported to produce luminescence yet. Bioluminescent
systems and FPs have been initially proven to be powerful toolkits as
biomarkers and biosensors in living plant cells. Recently, based on the
newly-discovered bioluminescent systems and enhancement of suboptimized
luminescence, the glowing plants were created (Reuter et al., 2020). The
glowing plants can be used as the illumination for reading and writing
(Kwak et al., 2017), though most of them are currently gloomy. As cool
light, bioluminescence and fluorescence are softer and more effective
compared with traditional artificial light, which makes glowing plants
as valuable source for aesthetics and lighting. However, the pratical
application of glowing plants was currently not availble due to
cytotoxicity of most bioluminescent systems, and lack of understanding
of optical characteristics and biosynthetic pathways of bioluminescent
systems. Solving those problems are helpful for developing the optimized
glowing plants in the future (Kaskova et al. 2016; Strack 2019).

Here, we summarized the literatures of rebuilding bioluminescent systems
and FPs to make glowing plants. The key points for design and
optimization of glowing plants, and the potential applications of
glowing plants are also proposed. These glowing plants might be useful
in scientific researching, as well as promising substitutes of
artificial light to light up the night sky in the future.

\textbf{Bioluminescence in plants: beyond as the biomarkers}

During past decades, tremendous efforts have been invested for the
development of optical non-invasive biomarkers in plant cells. The first
bioluminescent system that was introduced into plants is firefly
luciferase-luciferin system (Ow et al., 1986). Firefly luciferase can be
expressed independently or fused with proteins of interst in plant
cells, which provides a useful tool to study protein expression and
localization, and protein-protein interactions (PPIs) (Guan et al.,
2013; Sanchez et al., 2018). To detect PPIs, firefly luciferase is
splited as N- and C-terminal halves and fused with two candidates of
interactional proteins (Chen et al. 2008). However, firefly luciferin
could not be biosynthesized in plant cells yet, so that it have to be
supplied exogenously, which causes low cost-efficency.

To break those bottlenecks, several strategies were established,
including using FPs as alternative biomarkers and searching novel
luciferase-luciferin bioluminescent systems that can be completely
biosynthesized in plants. In 1995, the green fluorescent protein (GFP)
gene from \emph{Aequorea victoria} was successfully expressed
in\emph{Arabidopsis} , which brings novel revoluion in plant research
(Hu \& Cheng, 1995). Since then, FPs as tags are widely used in plants
to monitor protein localization \emph{in vivo} , recognize specific
plant cells and tissues, obtain cell-specific transcriptomes and record
plant cell fate selection (Ckurshumova et al., 2011). Spectral
characteristics of FPs could be altered to reduce autofluorescence
background from plant tissues. Various FPs covering most fluorescent
ranges (i.e. yellow, blue, cyan, green, and red) have been adapted for
plant cells (Blatt and Grefen, 2014). However, there are still problems
remained when using FPs, including cellular damage caused by excited
laser, signal weakening by plant tissues and migrating from
plasmodesmata due to its smaller molecular weight (Brunkard \& Zambryski
2017).

Another alternative strategy that developing novel bioluminescent
systems was emerging. After elucidation of the luciferase-luciferin
pairs original from bacteria and fungi, two distinguished optical
reporters have been developed from these systems and now accessible in
plant science. These systems have been described in their entirety and
could be biosynthesized in plant cells. However, due to cytotoxicity and
low photon yield of bacterial bioluminescent reactions in eukaryotes
(Kotlobay et al., 2018), since autoluminescent system was firstly
reported in \emph{Nicotiana tabacum} , only few bacterial
luciferase-luciferin pairs were reported in other transgenic plants (Cui
et al., 2014; Krichevsky et al., 2010). Fungal bioluminescent system is
an unique genetically encodable eukaryote luciferase-luciferin system,
which was introduced into plant cells recently (Khakhar et al., 2020;
Mitiouchkina et al., 2020). Less cytotoxicity and high luminescent
intensity make fungal bioluminescent system as one of the most promising
optical molecular tools (Reuter et al., 2020).

Nowdays, protein-directed revolution and synthetic biology boosted the
development for novel bioluminescent systems. Luciferase engineering
could be used to optimize the natural bioluminescent systems, such as
increasing bioluminescent intensity and stability. Rational designing
novel bioluminescent systems provides two representative cases, Nano
Luciferase (NanoLuc) (England et al., 2016) and Nano-lantern (Doerr,
2013). NanoLuc is a small subunit (19 kDa) from shrimp \emph{Oplophorous
gracilirotris} luciferase (Hall et al., 2012). Split NanoLuc was
developed to screen PPIs, which avoids imposing steric hindrance caused
by huge firefly luciferase halves (Wang et al., 2020). Nano-lantern is
an artificially designed luminescent protein fused with
enhanced\emph{Renilla} \emph{reniformis} luciferase and yellow FP Venus.
ATP production from chloroplast could be observed by Nano-lantern (Saito
et al., 2012). Today, fluorescence and bioluminescence is no longer a
new tool for molecular and celluar biology, but becoming a novel light
sources, with which glowing plants have been obtained.

\textbf{Ornamental glowing plants with FPs or nano-lanterns}

Ornamental glowing plants would be available when the fluorescence or
bioluminescence was bright enough. The reported bioluminescent plants
are summaried and shown in \textbf{Table 1} . The gene expression
casstte of FPs are easily to be integrated into genome and FPs can
accumulated enormously in plant cells, so it is feasible to generate
fluorescent plants. For example, CpYGFP, a yellowish-green FP from
marine plankton\emph{Chiridius poppei} , can be excited at 509 nm laser
line and emission was collected at 517 nm which is a red-shifted visible
light (Masuda et al. 2006). Commercial plants were transformed
with\emph{CpYGFP} gene, and green fluorescence was observed from the
flowers when emission filter were used (Sasaki et al. 2014;
Kishi-Kaboshi et al. 2017). Additionally, eYGFP and eYGFPuv, two
derivatives of CpYGFP, were expressed in the flowers of another
flowering plant, \emph{Petunia hybrida} . Green fluorescence was
macroscopically observed from the flowers with naked eyes, when they
were illuminated with visible and ultraviolet LED, respectively. Among
the various colors of flowers, white flowers contain less petal
pigments, indicating that less exciation light and fluorescence would be
absorbed. As a result, white flowers were chosen in these trials (Chin
et al., 2018). Many FPs maintain fluorescent stability under acidic
conditions, thus keeping high activity in the acidic intracellular
environment of higher plants that pH approximately 4.5-7.2. To enhance
fluorescence, nano-lanterns were introduced into plant cells. Recently,
green enhanced nano-lantern gene was transferred into \emph{A. thaliana}
, which could be lightened under the excitation of blue light. The
luminescence became remarkably brighter when the suitable substrate
furimazine was added (Furuhata et al., 2020). These results indicate it
is possible to obtain commercial ornamental fluorescent flowers.
Characteristics of FPs provides the fluorescent plants a specific
proposed implementations, such as dried fluorescent flowers and
fluorescent plant specimens. It is reported that embedding in fine
grained silica gels, the desiccated fluorescent flowers transferred with
\emph{CpYGFP} gene remained glowing for more than a year, because some
FPs are capable to generate fluorescence without water (Sasaki et al.,
2014). However, fluorescent plants utilized as alternative light sources
for street or reading lamp in completely darkness is currently
difficult, and these application might be satisfied by glowing plants
with luciferase-luciferin bioluminescent systems.

\textbf{Glowing plants with bioluminescent systems}

Up to now, three bioluminescent systems that origin from firefly,
bacteria and fungi have been reconstructed in plants. The firefly
luciferase-luciferin system is a kind of D-luciferin-dependent systems,
which is one of the most intensively studied bioluminescent systems
(Fleiss \& Sarkisyan, 2019). In the presence of Mg\textsuperscript{2+},
oxygen and ATPs, reduced firefly luciferin can be catalyzed by firefly
luciferase, and generate yellow-green luminescence. To prolong glowing,
CoA could be used to deoxidize the oxidized luciferin (Gosset et al.,
2020). Ow. et al. (1986) introduced \emph{Photinus pyralis} luciferase
gene into \emph{N. tabacum} and \emph{Daucus carota} for the first time.
Firefly luciferase was expressed during growing process of the
transgenic plant and accumulated in various plant organs, e.g., roots,
stems and leaves. When watering the tobacco with solution of firefly
luciferin and ATP, the substrate was transmitted to every tissues
through the vasculature and react with luciferase, leading to lightening
of the whole transgenic tobacco. Due to the technical difficulty to
synthesize firefly luciferin in plant cells, the firefly luciferins can
only be exogenously supplied. In 2017, a novel nano-technique named
pressurized bath infusion of nanoparticles (PBIN) was utilized to
introduce the whole firefly bioluminescent system. In PBIN, luciferin
and coenzyme A (CoA) were packaged into two different nano capsules, and
luciferase was linked onto the surface of silica-PEG nanocarriers. These
nanoparticles could reduce luciferin cytotoxicity and diminish chemical
denaturation of luciferase to some extent, causing a long light-emitting
duration of up to 8 hours. To transmit the whole firefly bioluminescent
system, the plant was immersed in solution containing the nanoparticles
in a closed pressured aqueous chamber, in which pressurization
delievered the nanoparticles into mesophyll cells through stomata. Once
these nanoparticle gathered in mescophyll cells, it glowed, and produced
the brightest glowing plants to date. The PBIN-based light-emitting
plants were also the only glowing plants which could be modulate ``on''
and ``off'' states when CoA- and dehydroluciferin-nanoparticles were
provided, respectively, thus providing viability as alternative light
sources (Kwak et al., 2017).

The second bioluminescent system is discovered in three Gram-negative
motile rods luminous bacteria genera, that is \emph{Vibrio}
,\emph{Photobacterium} , and \emph{Xenorhabdus} . The \emph{lux} operons
(\emph{luxCDABEG} ) are highly conserved through all luminous bacterial,
which encode the whole bacterial bioluminescent system (Close et al.,
2009). Gene \emph{luxA} and \emph{luxB} encode \selectlanguage{greek}α \selectlanguage{english}and \selectlanguage{greek}β \selectlanguage{english}subunits of
bacterial luciferase, respectively, and \emph{luxCDEG} encodes
biosynthesis pathway of tetradecanal. Krichevsky et al. (2010)
transferred the whole \emph{Photobacterium leiognathi} \emph{lux} operon
into tobacco chloroplast and obtained the first auto-luminescent plant.
Although only very dim green luminescence was observed, this
auto-emission needs neither exogenous luciferin nor optical excitation.
However, the cytotoxicity of the bacterial luciferin, long-chain fatty
aldehyde, is ineluctable to the eukaryotic cells. It is reported that a
low concentration of bacterial luciferin \emph{n-decyl} aldehyde can
cause toxity to many model eukaryotes, including mammalian and higher
plant cells (Hollis et al., 2001), which hindered application of
bacterial bioluminescent system as biomarkers or illuminants.

Recently, the third bioluminescent system originated from fungi was used
to generate auto-stronge-glowing plants.The biosynthetic pathway of
fungal luciferin is named caffeic acid cycle (Kotlobay et al., 2018). A
gene cluster encoded four key enzymes catalyze the caffeic acid cycle
in\emph{Neonothopanus gardneri} , including fungal luciferase (Luz),
hispidin-3-hydroxylase (H3H), hispidin synthase (Hisps), and
caffeylpyruvate hydrolase (CPH). Hisps is post-translationally activated
by another enzyme, NPGA (4'-phosphopantetheinyl transferase). Precursor
of fungal luciferin is hispidin, which can be convert to fungal
luciferin, termed 3-hydroxyhispidin. Then the luciferin is oxidized by
Luz to yield photons and oxy-luciferin, named caffelpyruvic acid,
followed by hydrolyzing the oxy-luciferin to pyruvic acid and caffic
acid. Caffic acid can be recycled to hispidin by Hips (Purtov et al.
2015; Oba et al. 2017). Fungal caffeic acid cycle shares three
intermediary metabolites with three major biosynthetic pathways of
vascular plants, including shikimate, lignins and flavonoid anthocyanins
condensed tannins. These common molecules make a bridge connecting the
gap between fungal caffeic acid cycle and the native biosynthetic
pathway in plant cells. As a result, it is reasonable to design a
sophisticated fungal luciferin synthetic pathway reconstituted into
tobacco metabolic routines (Mitiouchkina et al., 2019). Mitiouchkina et
al. (2020) created a luminescent \emph{N. tabacum} through synthetic
biology, which stably displayed green luminescence. Gene of \emph{Luz} ,
\emph{H3H} ,\emph{Hisps} , and \emph{CPH} were transferred in the
tobacco. The auto-luminescent tobacco was brighter than other reported
auto-light-emitting plants. Coninsistantly, Khakhar et al. (2020)
described the transiently transformation and expression of fungal
bioluminescent system in both model and commercial plant
species.\emph{NPGA} gene was also transferred besides the four gene
mentioned above. Stronge luminescence was generated from cotyledons,
leaves, and petals of these genetically modified plants. The fungal
bioluminescent system produces brighter light and shows no cytotoxicity
and growth inhibition to plant cells, compared with that employed
bacterial luminescent system (Kotlobay et al., 2018). However, drawbacks
are also existed on the plant-expressed fungal bioluminescent system.
For example, low pH and temperature in plant cells reduced photon yield
(Reuter et al., 2020).

\textbf{Synthetic routine of luciferin: footstone of auto-glowing
plants}

Here we define ``plantern'' (a chimera of ``plant'' and ``lantern'' in
both semantics and biology) as transgenic plant that is capable to
produce visible light need neither external illumination nor exogenous
substances, and the bioluminescence is bright enough to be observed with
naked eyes. Feasibility of designing ``planterns'' as streetlights have
been evaluated according to photosynthetic efficiency and luminous
energy output. To produce as much light as tranditional streetlights,
glowing plants have to output more than 1000 lumens by the transformed
firefly bioluminescent system. It was estimated that a fast-grow tree
glowing with the firefly luciferase-luciferin pairs only have to divert
approximately 0.3 \% of the stored energy to generate bright-enough
bioluminesence during the nighttime (Reeve et al., 2014). In addition to
producing light, planterns are also leveraged for whole-plant imaging
and studying spatiotemporal expression of genes during the entire
life-cycle, for limitations on delivering exogenous luciferin to the
whole plant and tissue would no longer be a bottleneck (Reuter et al.,
2020).

Rebuilding luciferin biosynthetic routine is the priority of generating
``planterns'', which could be achieved by introducing all genes
associated with luciferin biosynthesis (Krichevsky et al., 2010) or
integrating luciferin biosynthetic routine into native plant metabolic
pathway (Khakhar et al., 2020; Mitiouchkina et al., 2019). In the latter
situation, the complicated biosynthesis pathway could be simplified. The
unclarified intermediate steps would even be skipped if products of the
unknown enzymatic reaction have been found in plant metabolome. Once the
luciferin biosynthetic pathway in plant cells is reconstrcuted, common
plant genetic engineering technique would be used to make the transgenic
glowing plants (\textbf{Figure 1} ).

Besides those well-known bioluminescent systems that have been
reconstructed in plant metabolome, new bioluminescent systems were also
discovered recently. More alternatives of intracellular illuminants
would be available once unveiling the mysteries of newly-found
bioluminescent systems (Kaskova et al., 2016). Some of these systems
might be suitable for plant cells or whose synthetic pathways could be
reconstituted in plant metabolic routine. Recently, a novel yellow
bioluminescent system from annelid worms in the genus \emph{Tomopteris}
, kinds of pelagic polychaetes, was separated and characterized
(Glagoleva et al., 2020). The worm luciferin turned out to be
aloeemodin, which had been also discovered in plants, such as
\emph{aloe} and \emph{senna}(Heidemann et al., 1996). \emph{Arachnocampa
luminosa} , a New Zealand luminescent glowworm, can generate blue-green
light. The glowworm luciferase shares 31\% sequence identity with
firefly luciferase, but catalyzing an entirely new luciferin whose
biosynthetic pathway begins from xanthurenic acid and tyrosine (Watkins
et al., 2018). Dinoflagellate, notorious protist responsible for causing
the surface of the ocean to sparkle at night, produce bluish-green
gimmer under mechanical disturbance (Valiadi \& Iglesias-Rodriguez,
2013). The dinoflagellate luciferin is believed as derivative of
chlorophyll\emph{a} because of their similar molecular structures
(Topalov \& Kishi, 2001). Genes associated with reaction converting
chlorophyll\emph{a} into dinoflagellate luciferin could be introduced
into parts of chloroplasts when synthetic routine of dinoflagellate
luciferin is clarified.

\textbf{Optimization of ``planterns''}

One of the problems is low luminescent intensity, which hinders the
population of planterns. Though some glowing plants generated a bright
emission of 1.44 \selectlanguage{ngerman}× 10\textsuperscript{12} photons/s (Kwak et al. 2017),
many other auto-glowing plants produce a much dimmer luminescence of 1.3
× 10\textsuperscript{6} photons/s (Krichevsky et al., 2010) and 1.6 ×
10\textsuperscript{9} photons/s (Mitiouchkina et al., 2020), which is
only bright enough to see in entire darkness with naked eyes.
Enhancement of whole-plant glowing intensity could be considered as
follow. Bioluminescent intensity is determined by both characteristics
and accumulation of luciferase-luciferin pairs. Plant intracellular
conditions also interfere bioluminescent intensity. Once the
luminescence is produced, transparency window (TW) effects transmission
efficiency (Strack, 2019).TW can be measured and sketched by
spectrophotometer (Mitiouchkina et al., 2020). Because the TW is
effected by pigments, plant species, apparatus and growth status, the
bioluminescent spectrum should be altered according to TW.

As a result, the improvement of glowing intensity could be achieved from
two aspects, i.e., the optimization of bioluminescent systems and the
transgenic strategies. By engineering of luciferase, promotes
feasibility to enhance bioluminescent intensity, spectral
characteristics, pH and thermal stability by random mutagenesis,
site-specific mutagenesis and \emph{in scilicon} design (Branchini et
al., 2019; Fujii et al., 2007; Modestova \& Ugarova, 2016). Protein
fusion or spilt could also alter bioluminescent characteristics. A
chimeric firefly luciferase of North American firefly (\emph{Photinus
pyralis} ) and Japanese firefly (\emph{Luciola italica} ) luciferase
exhibited 1.4-fold enhanced bioluminescence quantum yield compared with
the wide-type firefly luciferases (Branchini et al., 2014). Nano-lantern
and NanoLuc are shown to improve luminescent intensity significantly,
though exogenously supplied luciferin is necessary. Similar nano-lantern
or NanoLuc might be developed based on the other bioluminescent systems
whose luciferin could be biosynthesized, e.g., fungal bioluminescent
system. Recently, as structural basis for the spectral difference was
gradually clarified, bioluminescent color could also be changed by
designing luciferin. It was reported that firefly luciferins with
elongated \selectlanguage{greek}π-\selectlanguage{english}system, such as phenyl or phenol, exhibit an obvious
red-shift of emission spectrum (Yao et al., 2020). It was reported that
firefly luciferin analog with less conjugated \selectlanguage{greek}π-\selectlanguage{english}system present
blue-shift in absorption and fluorescence (Pirrung et al., 2019). The
designed luminescent pairs provide more selections, and these luciferin
analogs might be able to be biosynthesized in plant cells. Given that
the potentially cytotoxicity and growth inhibition to higher plants
caused by bioluminescent systems, protecting groups were introduced into
luciferin is reported possible, which can decrease cytotoxicity and
enhance the accumulation (Yuan et al., 2017).

To optimize transgenic methodologies, substanial accumulation of
luciferase-luciferin pairs can be achieved via common genetic
engineering technique, such as codon optimization, inserting
translational enhancer and several tandemly ranging the gene cluster
(Sasaki et al., 2014). Engineering subcellular organelles (e.g.
chloroplast and vacuole) into specified ``scintillon'' is another
promising strategy. Increasing the accumulation of the whole luciferin
pathway can be achieved through the development of chloroplast
transformation technique (Kwak et al., 2019; Jin \& Daniell, 2015).
Bacterial bioluminescent system has been stably expressed in chloroplast
(Krichevsky et al., 2010). Maternal inheritance of the chloroplast
genome prevents genes from escaping into the environment through pollen
grains (Yu et al., 2020), which may helps popularize planterns as
alternative light sources in future (Callaway, 2013). Meanwhile,
vacuoles could be employed to accumulate FPs or luciferase-luciferin
pairs. Proteins associatd to bioluminescence can be fused with sequence
specific vacuolar sorting signals (Viegas et al., 2017). The potential
strategy to enhance the suboptimized glowing plants would be helpful for
designing better glowing plants in future.

\textbf{Perspective}

Glowing plants, especially ``planterns'', showed promising prespections
in detecting microbiome changes in built environment, and also can be
use as natural illumination (Reuter et al., 2020; Stewart et al., 2018).
The goal of generating ``planterns'' will promote the development of
plant biotechnology and benefit synthetic biology in return. Creating
``planterns'' will beone of the research hotspots because many
pioneering designs leave several suboptimization to be enhanced.
Commerical popularization of ``planterns'' will probably achieve another
success, given the fact that several genetic modified fluorescent
zebrafish species are still existing in worldwide aquarium despite
controversy (Knight 2003; Stewart 2006). We believe that it will be
possible to read or write under the luminescence of desk ``planterns'',
drive beneath the light of street ``planterns'', and enjoy the
mysterious atmosphere provided by garden ``planterns'' in the future.

\textbf{Acknowledgements}

This work was supported by the National Natural Science Foundation of
China (31900221), and Natural Science Foundation of Liaoning Province of
China (2020-MS-102).

\textbf{Conflict of Interest}

There is no conflict of interest.

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\textbf{Table. 1} . Summary of the reported glowing plants.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
Luminescence & Engineered Plants & Luminescent specices & Introduced
Genes and/or substrates & Reference\tabularnewline
\midrule
\endhead
FP-derivative & \emph{Torenia fournieri} & \emph{Chiridius poppei} &
\emph{CpYGFP} gene & (Sasaki et al., 2014)\tabularnewline
& \emph{Chrysanthemum morifolium} & \emph{Chiridius poppei} &
\emph{CpYGFP} gene & (Kishi-Kaboshi et al., 2017)\tabularnewline
& \emph{Petunia hybrida} & \emph{Chiridius poppei} & \emph{eYGFP} gene &
(Chin et al., 2018)\tabularnewline
& \emph{Petunia hybrida} & \emph{Chiridius poppei} & \emph{eYGFPuv} gene
& (Chin et al., 2018)\tabularnewline
Nano-lantern & \emph{Nicotinan benthamiana} & Artificial nano-lantern &
\emph{pH2GW7\_CT- Nano-lantern} gene & (Saito et al.,
2012)\tabularnewline
& \emph{Arabidopsis thaliana} & Artificial nano-lantern & \emph{green
enhanced Nano-lantern (GeNL)} gene & (Furuhata et al.,
2020)\tabularnewline
Firefly & \emph{Nicotiana tabacum} & \emph{Photinus pyralis} &
\emph{firefly luciferase} gene, solution of firefly luciferin and ATP &
(Ow et al., 1986)\tabularnewline
& \emph{Daucus carota} & \emph{Photinus pyralis} & firefly luciferase
gene, solution of firefly luciferin and ATP & (Ow et al.,
1986)\tabularnewline
& \emph{Spinacia oleracea} & unknown & three nanocarriers with firefly
luciferase, luciferin and CoA & (Kwak et al., 2017)\tabularnewline
& \emph{Eruca sativa} & unknown & three nanocarriers with firefly
luciferase, luciferin and CoA & (Kwak et al., 2017)\tabularnewline
& \emph{Nasturtium officinale} & unknown & three nanocarriers with
firefly luciferase, luciferin and CoA & (Kwak et al.,
2017)\tabularnewline
& \emph{Brassica oleracea} & unknown & three nanocarriers with firefly
luciferase, luciferin and CoA & (Kwak et al., 2017)\tabularnewline
Bacterium & \emph{Nicotiana tabacum} & \emph{Photobacterium leiognathid}
& \emph{luxCDABEG} & (Krichevsky et al., 2010)\tabularnewline
Fungi & \emph{Nicotiana benthamiana} & \emph{Aspergillus nidulans} and
\emph{Neonothopanus nambi} & gene of \emph{NPGA}, \emph{H3H},
\emph{Hisps}, \emph{Luz}, and \emph{CPH} & (Khakhar et al.,
2020)\tabularnewline
& \emph{Arabidopsis thaliana} & \emph{Aspergillus nidulans} and
\emph{Neonothopanus nambi} & gene of \emph{NPGA}, \emph{H3H},
\emph{Hisps}, \emph{Luz}, and \emph{CPH} & (Khakhar et al.,
2020)\tabularnewline
& \emph{Solanum lycopersicum} & \emph{Aspergillus nidulans} and
\emph{Neonothopanus nambi} & gene of \emph{NPGA}, \emph{H3H},
\emph{Hisps}, \emph{Luz}, and \emph{CPH} & (Khakhar et al.,
2020)\tabularnewline
& \emph{Dahlia pinnata} & \emph{Aspergillus nidulans} and
\emph{Neonothopanus nambi} & gene of \emph{NPGA}, \emph{H3H},
\emph{Hisps}, \emph{Luz}, and \emph{CPH} & (Khakhar et al.,
2020)\tabularnewline
& \emph{Catharathus roseus} & \emph{Aspergillus nidulans} and
\emph{Neonothopanus nambi} & gene of \emph{NPGA}, \emph{H3H},
\emph{Hisps}, \emph{Luz}, and \emph{CPH} & (Khakhar et al.,
2020)\tabularnewline
& \emph{Petunia hybrida} & \emph{Aspergillus nidulans} and
\emph{Neonothopanus nambi} & gene of \emph{NPGA}, \emph{H3H},
\emph{Hisps}, \emph{Luz}, and \emph{CPH} & (Khakhar et al.,
2020)\tabularnewline
& \emph{Rosa rubiginosa} & \emph{Aspergillus nidulans} and
\emph{Neonothopanus nambi} & gene of \emph{NPGA}, \emph{H3H},
\emph{Hisps}, \emph{Luz}, and \emph{CPH} & (Khakhar et al.,
2020)\tabularnewline
& \emph{Nicotiana tabacum} & \emph{Neonothopanus nambi} & gene of
\emph{H3H, Hisps, Luz and CPH} & (Mitiouchkina et al.,
2020)\tabularnewline
\bottomrule
\end{longtable}

NPGA, 4'-phosphopantetheinyl transferase; H3H, hispidin-3-hydroxylase;
Hisps, hispidin synthase; Luz, fungal luciferase; and CPH,
caffeylpyruvate hydrolase.

\textbf{Figure legend:}

\textbf{Figure 1} . Flow chart of creating auto-glowing
plants.\textbf{(A)} The representative native bioluminescent system is
elucidated. \textbf{(B)} The optimized biosynthetic pathway of luciferin
is then reconstituted into plant metabolomic rountines. \textbf{(C)} The
associated key genes are amplified, cloned into plasmids, and
transformed into the plants. \textbf{(D)} Once obtaining glowing plants,
luminescent characteristic and effects on these transplants will be
tested.\selectlanguage{english}
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