By Nathan Smith
A plant, a fungus, and a virus live together in an environment inhospitable to each partner on their own. This isn’t an absurdist sitcom that’s been written whilst high in the garden, but a genuine biological phenomenon.
The plant, a type of grass known as Panic Grass (Dichanthelium lanuginosum), can grow at temperatures of up to 65C (for a point of comparison, the lethal temperature for humans is about 40C). It is found growing in Yellowstone National Park but only when it has a fungal symbiont Curvularia protuberata and this in turn is ‘infected’ with Curvularia thermal tolerance virus (CThTV).
The ecological love-triangle was shown to be necessary for the plant-partner’s survival. This was done by infecting the plant with a ‘cured’ fungus (one that lacks the virus) and comparing it to a plant with both fungus and virus and a plant with no symbionts. The plants were then treated to growing conditions of 65C for 10hrs and 37C for 14hrs. At the end of the treatment, only plants with both partners remained healthy. Furthermore, all plants with both symbionts remained alive whereas the majority of the plants with only the fungus or nothing at all died before the experiment was completed.
However, panic grass isn’t that important or useful to us. It’s not eaten, nor is it cultured to produce fibre or biofuels. So is there any point to this knowledge? Well, the tri-kingdom system can be translated into more economically important crops. It has been shown that the fungal symbiont can colonise the roots of tomato plants and provide protection against higher temperatures, though not to the same extent as is provided to panic grass. It also suggests that the adaption to this system is widespread in nature, as panic grass and tomatoes diverged relatively early in the evolution of plants.
This certainly is hot stuff!