While studying California dryland biocrusts (communities of living organisms which inhabit the surface of soils), researchers from University of California Riverside found something unlikely inside moss.
Not only could the discovery completely rewrite what we know about moss biology, but it could also offer an insight into how plants first moved from the oceans onto land around 470 million years ago.
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For a long time, scientists have taken one fact for granted: fungi and moss don’t establish symbiotic relationships with each other (moss would be the only major lineage of land plants with that trait).
A new study published in the journal New Phytologist argues this might be a premature assumption. Given the millions of years of evolutionary history of both mosses and fungi, it’s quite unlikely they wouldn’t evolve any symbiosis.
To investigate this, researchers collected samples of the same species of moss from the scorching landscapes in the Mojave and Sonoran deserts, as well as less arid climates, to compare them. They wanted to find out whether differences in climate might coincide with differences in fungal communities inside moss.
To figure that out, they ground up moss samples, searched for fungi DNA within them – and struck gold. They were particularly surprised to encounter mycorrhizal fungi, which cannot survive without a plant host.
The fungi inside moss collected from the desert wasn’t the same as the fungi inside moss grown in more forgiving conditions. And perhaps more interestingly, the species of fungi inside the dryland mosses didn’t match the ones found in the dirt near them – suggesting the connection wasn’t random contamination, but perhaps a more deliberate relationship.
“We suspect that certain fungi are more helpful for surviving hotter, drier climates,” said Kian Kelly, a doctoral researcher University of California Riverside.
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Fungi DNA in moss isn’t enough to establish a symbiotic relationship, so the researchers dug deeper by turning to microscopy. They stained moss tissue with a blue dye that sticks specifically to fungi and found branching fungal structures resembling tiny tree-shaped formations fungi normally build within plant roots to swap nutrients.
They weren’t the same, though – mosses don’t have roots, so the structures actually appeared in leaves instead. Further studies are needed to establish whether the two organisms are swapping nutrients before the relationship can officially be declared a true symbiosis.
Importance of moss
Drylands (zones defined by the scarcity of water) encompass around 45 per cent of Earth’s land surface, and biocrusts cover up to 70 per cent of those drylands, acting out a crucial role in the race against climate change.
Mosses alone absorb 6.4 billion tons of carbon annually – but moss biocrusts are some of the most susceptible to climate change. Biocrusts in general are predicted to experience up to 39 per cent land area loss in the next 45 years.
It’s crucial we understand as much as we can about the biological intricacies of moss to help predict the effects of rising aridity in the drylands – and hopefully mitigate them. If the symbiotic partnership between moss and fungi is confirmed, it could also help scientists better understand the origins of life on Earth.
“The desert is full of things people overlook. Sometimes, the biggest surprises are the ones growing quietly beneath our feet,” said Kelly.
Read the full findings here.
Top image: the Mojave Desert. Credit: Gary Yeowell/Getty Images
