Could glow-in-the-dark plants replace streetlights?

Getting the Green Light

They say that mighty oaks from little acorns grow. Lighted oaks require a little help from science though.

The fluorescent marker research underlying the Glowing Plants initiative was pioneered by 2008 Nobel Prize winners Osamu Shimomura, Martin Chalfie and Roger Y. Tsien, but work on tracking gene expression using green fluorescent protein (GFP) really blossomed in the 1990s. The protein, which glows when exposed to ultraviolet light, soon initiated a sea change in molecular and cellular biology, medicine and pharmacology, and helped plant the seed for fledgling biotech industries such as biosensors and bioinformatics [sources: Evans; Lee and Min; Nobel Foundation; Timmer; Tsien].

But plants that require a black light to shine aren't much use for driving or reading. Such applications require a light-shedding chemical reaction, a kind of germinating glow stick.

In 1986, University of California at San Diego (UCSD) researchers created just that when they modified a tobacco plant to produce an enzyme called luciferase. As any firefly can tell you, when luciferase reacts with ATP, an energy-storing molecule used in metabolism, and luciferin, an organic molecule, it emits light [source: Monastersky].

UCSD's plant was limited in one important regard, however: It didn't make its own luciferin, so it was unable to, so to speak, glow it alone. In 2010, researchers at Stony Brook University overcame this limitation by slotting six luciferin-coding genes from bioluminescent marine bacteria into genetic material located in the plant's chloroplasts (plant structures that hold photosynthetic pigment). Et voila, autoluminescent tobacco -- presumably for recovering smokers who like to light up without lighting up [sources: Evans; Krichevsky et al.; Paramaguru; Pollack].

Unfortunately, the Stony Brook plant shone so dimly it required five minutes in darkness for human eyes to perceive it [source: Pollack]. Worse, the glow gradually self-destructed as the luciferin fueling it was converted into oxyluciferin [source: Swain].

One possible way out of this chemical cul-de-sac came in 2010, when a University of Cambridge iGEM team (see sidebar) inserted genes from fireflies and bioluminescent bacteria into modified E. coli, creating a process that recycles oxyluciferin back into its glow-friendly precursor. Their process also boosted light output sufficiently that a wine-bottle-sized bacterial culture emitted enough light to read by. Finally, Evans and company had the pieces they needed for a renewable and self-sustaining plant light [sources: Evans; iGEM; Swain; Timmer].

But whereas glowing markers encompass vital research and medical applications, the point of a glowing tree -- even one with potentially positive environmental effects, assuming Evans is right -- leaves many observers stumped.

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