NO FUNGI, NO US

THE EPIC TALE OF HOW FUNGI MADE OUR WORLD

Cosmos - - Contents - GALLERY WORDS AND CU­RA­TION BY ANNAMARIA TALAS

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.

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