Are Mushrooms Plants?  The Answer Will Shock You…

HOW DARE YOU PROFANE THE SACRED NAME OF PLANTAE ?!?

Mushrooms are fungi.  Fungi are not plants.

The evolutionary origins of fungi are like Kuwait or the Backstreet Boys: people fought over it a lot in the 90’s.  Now we know that fungi aren’t even closely related to plants.  Fungi and animals share a unique evolutionary history; fungi and plants don’t.

Allow this stock photo of a helpful woman on a cell phone to explain.

DNA sequences, RNA sequences, and biosynthetic pathways agree: Mushrooms are more related to you than they are to plants.

But you’re excused for neglecting your dear Uncle Puffball.  Mycology, or the study of fungi, used to be considered a part of botany, the study of plants.

The thing you call a “mushroom” and eat on pizza, by the way, is the sex organ of the fungus, also known as a “fruiting body.”  Most of the fungus actually lives underground, eating dead stuff through a web of moist, spindly threads called hyphae.  The fungus’s sex organ, the mushroom, emerges only to spray reproductive spores into the air as it slowly withers.  Yum!

To reiterate:  Plants.  Fungi.  Two separate things.

Except when something incredible happens:  LICHENS!

You may have seen these buddies on old walls or gravestones.

Lichens aren’t a fungus or a plant.

They’re both.

Specifically, they’re a symbiosis, in which different organisms live together long-term and argue over who does the dishes.

 

In lichens, a photosynthesizing partner (often green algae) and a fungal partner (often ascomycetes) come together.  The algae photosynthesizes and the fungus protects the cells.  The lichen looks nothing like the individual plant or the fungus.

 

Scientists used to believe that lichens consisted of only one fungal partner and only one photosynthesizing partner.  But last year a research team reported that many lichens are actually a stable threesome, with an additional species of fungi.  Woo woo!  Whole communities of microbes also live inside lichens.

 

 

Mycorrhizae are also a fascinating plant-fungus symbiosis; I’ll write about them later.

TL;DR:  Mushrooms are not plants, they’re fungi.  Fungi are more genetically similar to humans than they are to plants, even though they look like plants.  Fungi and plants live symbiotically in lichens (and elsewhere).  Mushroom pizza is delicious.

 

Sources & Further Reading:

Borchellini, C., Boury-Esnault N., Vacelet, J., Le Parco, Y.  1998.  Phylogenetic analysis of the Hsp70 sequences reveals the monophyly of Metazoa and specific phylogenetic relationships between animals and fungi.  Molecular biology and evolution 15.6: 647-655.

“lichens.”  A Dictionary of Biology (7^th edition), edited by Robert Hine and Elizabeth Martin.  Oxford University Press, 2016.

Spribille, T., Tuovinen, V., Resl, P., Vanderpool, D., Wolinski, H., Aime, M.C., Shneider, K., Stabenheiner, E., Toome-Heller, M., Thor, G., Maryhofer, H., Johannesson, H., McCutcheon, J.P.  2016.  Basidiomycete yeasts in the cortex of ascomycete macrolichens.  Science 353.6298: 488-492.

Wainwright, P. O., Hinkle, G., Sogin, M.L., Stickel, S. K. 1993.  Monophyletic origins of the metazoa: an evolutionary link with fungi.  Science 260.5106: 340.

Credit for best lichen photo on Wikimedia Commons to Norbert Nagel.

Note: In lichens, sometimes the photosynthesizing partner can be cyanobacteria.  Cyanobacteria is not a plant.  Plants have a complicated relationship with cyanobacteria because they kidnapped it for plastids.  (See “endosymbiosis”)