NO FUNGI, NO US

THE EPIC TALE OF HOW FUNGI MADE OUR WORLD

ANNAMARIA TALAS tells the epic tale of how fungi made our world.

The button mushroom in your local grocery store probably doesn’t inspire a sense of awe. It should. It’s just a visible outpost of a largely hidden, alien-like kingdom that rules all life on land: fungi.

THEY RANGE IN SIZE from microscopic yeast to the largest organism alive – the honey fungus Armillaria solidipes whose underground network spans 1662 football fields! After bacteria, they are the most ancient land-based life. According to the latest estimate from mycologist Mary Berbee of the University of British Columbia, they’ve been here for about a billion years, predating the first land plants by at least 500 million years.

They eked out a living mining rocks, extracting minerals, dining on bacteria and fighting them for scarce resources. They became masters of survival.

And then around 450 million years ago, a group of green algae splashed up on to the shoreline. Fungi extended a helping hand, sending their filaments into the plant’s tissue to provide them with a lifeline for water and minerals. The algae repaid the favour by providing sugar.

The relationship was remarkably intimate: the fungal filaments penetrated the very cells of the plant, forming a treelike structure that’s known as ‘arbuscular mycorrhiza’. Just how this interspecies collaboration was established has been an enduring secret of nature.

The mystery was solved in 2015 when evolutionary microbiologist Pierre-marc Delaux, now at Université Paul Sabatier, Toulouse, revealed that the algal ancestors of land plants, a group called ‘charophytes’, were equipped to communicate with fungi well before they encountered them.

Unlike other algae, these charophytes possessed a unique set of ‘signalling’ genes. This enabled them to detect and work with these co- operative fungi. Ever since, nearly every land plant has been nurtured by its symbiotic fungi.

The greening of land set in motion a trajectory that led to the richness of life around us. Working with fungi, the first plants changed the atmosphere and sparked the evolution of terrestrial ecosystems with all their plants and animals.

So next time you happen to glance at a button mushroom in the grocery store, pause and reflect: you are gazing at one of the conductors of the symphony of life on land.

If it wasn’t for fungi, we wouldn’t be here.