Plants grow brightly with mushrooms

It’s feasible to create plants that produce sustainable luminescence that we can see, scientists suggest.

Credit: Planta

The bioluminescence found in some mushrooms is metabolically similar to the natural processes common among plants, they say, and by inserting DNA obtained from said mushrooms into plants you can make them glow more brightly than possible previously.

And they glow continuously throughout their lifecycle, from seedling to maturity.

The research involved 27 scientists from Russia, the UK and Austria. They worked with tobacco plants because of their simple genetics and rapid growth but say the benefits of mushroom bioluminescence have broad application.

The “how” is outlined in a paper in the journal Nature Biotechnology. The “why” is that it has the potential for practical (observing the inner workings of plants) as well as aesthetic purposes.

The new plants produce “a much brighter and more steady glow, which is fully embodied within their genetic code”, notes co-author Keith Wood. 

The story goes like this. Although mushrooms are not closely related to plants, their light emission centres on an organic molecule, called caffeic acid, which all plants need for making cell walls. 

This molecule produces light through a metabolic cycle involving four enzymes. Two convert the caffeic acid into a luminescent precursor, which is oxidized by a third to produce a photon. The fourth converts the molecule back to acid to start the cycle again.

In plants, caffeic acid is a building block of lignin, which helps provide mechanical strength to the cell walls. It is thus part of the lignocellulose biomass of plants, which is the most abundant renewable resource on Earth. 

As a key component of plant metabolism, caffeic acid (which is not related to caffeine) is integral to many other essential compounds involved in colours, fragrances, antioxidants, and so forth. 

By connecting light production to this molecule, the glow emitted by the plants provides an internal metabolic indicator. It can reveal the physiological status of the plants and their responses to the environment. 

For instance, the glow increases dramatically when a ripe banana skin is placed nearby (which emits ethylene). Younger parts of the plants tend to glow most brightly, and the flowers are particularly luminous. 

Flickering patterns or waves of light are often visible, revealing active behaviours within the plants that normally would be hidden.