Making Mushrooms

It's fairly well-known that mushrooms are only a small portion of a much larger fungal organism. Mushrooms (in all their bewildering variety of shapes, sizes, colors, textures, and edibilities) are relatively short-lived fruiting structures, much like apples on an apple tree. The main body of a fungus (the tree, so to speak) is a network of fine hairlike structures called a mycelium, which commonly spreads through the soil, or lives within a rotting tree. A single mycelium living in the soil may cover hundreds of acres and live for thousands of years. That's a pretty impressive 'apple tree'!

What's less well-known is the odd way that fungi pass their DNA from one generation to the next. To understand this, we need to discuss some genetics  - but don't worry, this won't get very technical.

Genetics is the study of DNA. I'm sure you've heard of DNA, but you may not know what it is, or why it's so important. In the simplest terms, DNA is a chemical that contains a code within its three-dimensional structure.

This code explains how to make protein molecules.

So what? That doesn't sound very impressive, does it? Ah, but proteins are extremely important for all life on Earth. Your body, alone, contains over 20,000 different kinds of proteins. Everything that you do, and every part of your body, depends on proteins. Your body is largely composed of structural proteins, while mechanical proteins perform every action that you can imagine doing -  from running, to breathing, to laughing, to imagining. You quite literally ARE your proteins.

The living cells in your body make all your proteins, but your cells need instructions that tell them what proteins to make, when to make them, where to make them, and how much of them to make. That's what DNA is. DNA is a set of instructions that tells living cells everything they need to know about making the right proteins at the right time in the right place in the right quantities. DNA is like a cookbook, and cells are the chefs who use the cookbook's recipes to create their masterpieces.

Or, for a more colorful analogy, imagine that DNA is a book of spells, and your cells are the wizards who cast spells from that book.

(The AI that generated this image of a wizard and her spell books seems to have gotten books confused with candlesticks. Although perhaps it's normal for spell books to have flames coming out of them. The AI also suffered from a common inability of AIs to draw hands accurately.)

The DNA in your body tells your wizard-cells how to make all of the proteins that create... well... you! Your DNA is essentially your own personal 'spell book', unique from that of every other person and every other creature.

Now, no self-respecting wizard would limit themselves to a single solitary spell book. The magical lady-wizard in our picture above has an entire bookshelf of them. More spell books means more instructions for more spells. And this gives the wizard more diversity in what she can accomplish.

Your cells contain two separate 'spell books' of DNA. Where did your cells get these two books? You received one book from your Mom, and one book from your Dad. Each book - on its own - contains one complete set of instructions for 'how to make a human'.

However, each book contains variations on the theme of what a human is like. Perhaps the DNA from your Mom explains how to construct red hair and blue eyes, while the DNA from your Dad explains how to construct black hair and brown eyes. Your wizard-cells draw from this diversity to create the unique individual that is YOU.

When you have children, you pluck a random mish-mash of instructions from each of these two books, stick them together into one complete 'how to make a human' book, and pass this newly-minted book on to your offspring in either an egg or a sperm. The structures in human bodies that do this mish-mashing are the ovaries and testes.

A couple of fancy terms to know. Cells that contain two 'spell-books-worth' of DNA are called diploid (from the Greek word diplous, meaning double). Cells that contain only one 'spell-book-worth' of DNA are called haploid (from the Greek word haploos, meaning single.

Your body cells are diploid, while the eggs or sperm you create are haploid. When a haploid egg and a haploid sperm combine, the result is a diploid organism once again, and the cycle continues.

What does all this have to do with fungi? Don't worry, we're getting there.

Most of the human lifecycle is spent in a diploid state. From conception to death, a human's cells are diploid. This time period may last 100 years or more. By contrast, the haploid portion of a human lifecycle is very brief. Once released from an ovary, a mature haploid egg only survives about a day unless it's fertilized. Sperm can last a bit longer - perhaps as many as five days. Still, that's a vanishingly-small period of time to spend being haploid, when compared to many decades of being diploid.

Further, eggs and sperm don't do much during those few days that they're alive and on their own. Sperm are good swimmers, but swimming is about all they do. Eggs don't even do that.

Okay, so the AI image generator didn't know how to draw a picture of a sperm and an egg. The closest I could get was a picture of an eel (sperm-like) and a jellyfish (egg-like). Even so, that's a terrible eel. I haven't decided whether it's cute or downright creepy.

Let's boil this down into a genetic slogan. For humans, Diploid Is Where It's At. Diploid is where all the interesting work of living gets done. By contrast, Haploid is Lame. Being haploid (for a short time) is essential, true. But all the good stuff happens when you're diploid. You know - stuff like growing, learning, laughing, and mushroom hunting.

Fungi don't share this attitude. In fact, they take the opposing viewpoint. Fungi spend most of their lifetime haploid. That centuries-old mycelial network spanning acres of forest under your feet? It's cells are haploid - just like sperm and egg cells in humans.

The diploid portion of a fungus's lifecycle is brief and minimal. If you look for diploid cells in a fungus, the only place you'll find them is the spore-producing structures of a mushroom. These diploid structures only have one job. They pluck random mish-mashes of instructions from their two different 'DNA spell books', stick them together into single books, and pass those newly-minted books on to haploid spores - each of which can grow into a haploid mycelium on its own.

Remember, the structures in human bodies that do this 'DNA mish-mashing' are the ovaries and testes. In humans, these diploid structures are only a small portion of a much larger diploid body, and it's these bodies that get up to all sorts of interesting things - driving cars, reading blogs, painting toenails.

In fungi, the diploid mish-mashing structures are tiny, and do nothing other than make spores. That's it. No driving, reading, or painting. It's the spores themselves (analogous to eggs and sperm) that grow into complex bodies and do things... although I've never seen a mycelium drive a car or paint its toenails.

If humans lived this way, what would it look like? Well, imagine that sperm and eggs are the dominant forms of human life. Each haploid sperm and each haploid egg grows into a multicelled, completely independent organism in its own right - no fertilization, no combining with another haploid cell. These sperm- or egg- derived, multicelled, haploid entities are the ones that that drive cars, write sonnets, and spend too much time reading social media.

Suppose a free-living, multicelled, haploid sperm-human meets an equally free-living, multicelled, haploid egg-human, and they fall in love. What will they do to... er... consummate their love, so to speak?

Mr. Sperm and Ms. Egg will come into physical contact, touching one another. Some of their cells will actually fuse together (going through a process analogous to fertilization), and create a small patch of diploid cells. This patch of diploid cells remains attached to both 'parents'. The cells within this patch rapidly do the 'spell-book-mish-mashing' process, and create new haploid sperm and new haploid eggs. These sperm and eggs fall away from the two parents, disperse, and grow into new, multicelled, haploid adults.

When Mr. Sperm and Ms. Egg are done with this process, the diploid reproductive tissue degenerates, and the two parents go their separate ways.

In fungi, the diploid stage that we spend most of our lives experiencing is reduced to little more than an analogue of an ovary or a testis. The haploid stage that is so brief in our lives is where fungi spend most of their existence, growing into multicelled analogues of eggs and sperm.

Why such a seemingly bass-akward system? Well, to be honest, we're actually the backwards ones. Most forms of life on Earth that reproduce sexually do it in a manner similar to fungi. In most sexually-reproducing organisms, the haploid stage is dominant, and the diploid stage is brief.

Animals are really the only ones that have a dominant diploid stage and a brief haploid stage. Plants are similar to animals... kind-of. Their diploid/haploid genetics is actually even weirder than fungi, but that's a topic for another time.

Why are animals different when it comes to this whole diploid-haploid-sexual reproduction system? It may have to do with our very complex multicelled bodies.

Most sexually-reproducing species are simple and single-celled. Fungi are multicelled, but their mycelial bodies are still rather simple - they don't produce arms, muscles, corneas, or teeth for example (except in science fiction). In order to create complex organs and tissues like those, perhaps more than one spell book is necessary. Remember, when wizard-cells contain more than one spell book, they have more diversity in what they can accomplish.

There may be other reasons why animals live much of their lives in a diploid state, when most other organisms don't. Diploid versus haploid lifestyles are a fascinating topic of continued scientific investigation.

And one last interesting tidbit, to bring this whole topic of DNA, proteins, and mushrooms full circle. You probably know that some mushrooms are deadly, but you may not know why. There are many different fungal toxins that can wreak havoc in all sorts of ways. Perhaps the most insidious is a group of chemicals called amatoxins.

Amatoxins do one very simple thing. They clog up the protein-making machinery within kidney and liver cells. This prevents those cells from making any new proteins. The toxins don't kill the cells directly. But, proteins are so essential for life, that when liver and kidney cells lose the ability to make new proteins, the cells eventually die.

There's no reversing this process. There's no way to unclog the protein-making machinery in kidney or liver cells. When someone consumes amatoxins, the damage to their liver and kidneys is permanent. Organ transplants may be necessary.

Did you make it this far? Impressive! As a reward, here's a gallery of intriguing mushrooms found in the preserve over the past few years. I haven't listed any species identifications, because fungi can be tricky to identify. The process often involves microscopic examination of spores.

You can click on each picture for a larger view.