Undoubtedly, the invention of artificial light in the XIXth century brought enormous advantages to our lives, making simply unconceivable the idea of a city without abundant electric light in its homes, streets, restaurants, cinemas and stores. Only recently, as a consequence of our shifting to a 24h society, the “dark side” of the lighting has been taken into consideration. Light pollution has become a critical issue, responsible for interferences and damages at an ecosystemic level, other than the cause of around one quarter of electricity consumption worldwide . The reduction of artificial light consumption, and of its consequent CO2 production, looks then as an important step towards a more sustainable and “green” lifestyle.
http://static.dezeen.com/uploads/2014/03/Glowing-Tree-Urban-setting-Roosegaarde-Dezeen_644.jpg (Studio Roosegaarde)
Among the different solutions addressed to solve the light pollution concern, and the correlated energetic waste, plant biologists and geneticists propose a fairly creative and totally green (that is really the case!) perspective: trees streetlamps! It seems indeed possible, thanks to the advances in the knowledge of chemistry and biotechnology, to produce bioluminescent plants, capable of lightning streets. As very efficient solar-powered lights (in addition to being very attractive), gardens, parks and boulevards might be lit by the natural light emitted by the very plants living in there . It is indeed natural night, since bioluminescence is a common phenomenon in wildlife, mostly associated with fungi, bacteria, insects, jellyfish and marine animals . Bioluminescence can be found in different parts of the world such as Puerto Rico (Fajardo Bio Bay), Japan (Toyama Bay), the United States (San Juan Island, Washington), New Zealand (Waitomo), Wales (Anglesey), Australia (Gippsland Lakes) and many more! 
The chemical reaction at the base of bioluminescence is the light-emitting pigment luciferin. When luciferin undergoes an oxidative reaction with the enzyme luciferase, light is generated as a secondary product, because the produced oxyluciferin molecule displays an electronically excited state. The release of a photon (light) occurs as oxyluciferin goes back to the ground state. Displaying different chemical configurations, luciferins and luciferases forms are responsible for the green/yellow/orange light of fireflies, the blue light of squids and the green light of brittle stars. 
Scientists have already tried to recreate this phenomenon in plants. In the 1980’s, a firefly’s luciferase gene had been transferred in tobacco cells, but since this species does not produce luciferin, only a temporary glow was possible, after the external supply of luciferin through vaporization on leaf surface . Only in 2010 the first bioluminescent plant has been produced, when researchers successfully transferred the entire bacterial luciferin/luciferase pathway in the genome of tobacco plantlets . This glowing plant prototype has been called Starlight Avata. The reference to the science fictional movie “Avatar” is quite clear. In 2009, the director James Cameron introduced us to the amazing world of Pandora, a world filled with vivid colors and amazingly luminescent flora and fauna: in the movie, bioluminescence plays indeed a main role. Although the film is set in the mid-22nd century, the possibility of a bioluminescent environment is not that far away. The generation of the glowing plant Starlight Avatar sparkled the imagination of many scientists, and different research groups are discussing about the multiple applications of bioluminescent plants and trees on our everyday life. At this point, it doesn’t seem absurd the idea of using bioluminescent plants as security nightlights, as an esthetically pleasant -and economically advantageous- system for public lightning as well as in transportation, marking driveways and highways with natural light that does not require electricity. In the long term it will be even conceivable to make plants glow differently in response to environmental conditions, making them effective environmental sensors (e.g. glowing as indicator of air pollution level) .
These “living lamp plants” may be soon a symbol of the incoming future, where sustainability will be the key-word in order to face nowadays great challenges. In the meantime, researchers are working to light up the way!
 Gaston KJ, Duffy JP, Gaston S, Bennie J and Davies TW. Human alteration of natural light cycles: causes and ecological consequences (2014). Oecologia; Vol. 176 (4): 917–931
 Haddock SHD, Moline MA and Case JF. Bioluminescence in the Sea (2010). Annual Review of Marine Science; Vol. 2: 443-493. DOI: 10.1146/annurev-marine-120308-081028
 Ow DW, De Wet JR, Helinski DR, Howell SH, Wood KV and Deluca M. Transient and stable expression of the firefly luciferase gene in plant cells and transgenic plants (1986). Science. Vol. 234 (4778):856-859.
 Krichevsky A, Meyers B, Vainstein A, Maliga P and Citovsky V. Autoluminescent Plants (2010). PLoS ONE; Vol. 5, e15461. doi:10.1371/journal.pone.0015461