Mother Nature’s Kama Sutra, Part 3

My favorite mushroom-bearing fungus, Schizophyllum commune, has not just a few, but thousands of sexes. This little wood-rotter caught my attention back in the fifties when my mentor (later, my husband) Red Raper began to study it at the University of Chicago. After a few year’s time-out from science, raising our new born offspring, I went back to the lab and collaborated with Red on this research and have not lost interest since.

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Paired collections of specimens from all over the world revealed thousands of different compatible mating-types. We and associates located two genetic loci involved, each of which were later shown to contain multiple genes.

Let’s say you’re a member of this little critter whose job it is to rot fallen logs in the forest and recycle carbon. Then you would be one of over 20,000 different sexes. If you traveled all over the world and mingled with others of the species, you would be able to mate and reproduce with up to 98% of your kinfolk.

Unlike a human, you could not perceive possible mates just by looking at them. To find attraction, you would have to get up close and sense their pheromones to see if any of them fit your receptor. Compatibility would lead to merger. But that’s not all. After union, you must then couple your special molecules (called homeodomain proteins) in just the right way with another set of different but similar molecules from your chosen mate. Those bound proteins then turn on a cascade of genes leading to sexual reproduction within both partners. In this system not only you make mushrooms bearing the babies but so does your mate—fertilization is a two-way street.

How can this be? Well, nature devised a way to produce a large variety of pheromones, pheromone receptors, and different types of special homeodomain proteins to fit together as locks and keys opening or closing the gates to sexual procreation. Everyone carries them and most of these molecules couple properly with those of other individuals, but not in self. The encoding genes evolved in such a way as to keep the gates closed within each individual , thus preventing inbreeding, but to open them in others, thus promoting promiscuous outbreeding.

Now that you’ve imagined yourself with such procreative abilities, what do you think?

Might it be fun or just utterly unmanageable? Schizophyllum seems to manage admirably—its offspring travel by jet stream all over the planet and do their life-sustaining jobs wherever wood is found. Many other mushroom-bearing fungi function similarly.

Too fanciful for you? Ah well, let’s make it simpler like sex in the edible button-mushroom, Agaricus bisporus, found in the supermarket as well as in the woods and meadows. Now you can do it all on your own as an hermaphrodite but without any need for sex organs. You can make your own gametes of two different types and fertilize yourself. How less complicated can it be? But sexually reproducing your own kind over and over in the absence of a partner might be just a bit too boring. It borders on reproduction without any sex at all as in some other members of the fungal kingdom. Recent discoveries, however, have revealed worn out remnants of sex genes in some so called asexuals. They must have been sexy sometime in the past. Now without those formally functional genes, these fungi reproduce by cloning.

Nevertheless, sex is generally compelling and ubiquitous.

Other strategies exist in fungi such as that in Cyphellopsis anomala where one can have it both ways—mate with a suitable partner should one be available or, if not, have sex all by yourself.

In more prosaic fashion, you could function as does the pink bread mold Neurospora crassa with just two sexes, and one-way fertilization—rather like we humans but without all the same accouterments. This fungus grows not only on bread, but in nature—preferably in burned-out woods.

The fungi seem a major testing ground for all ways possible to reproduce sexually.

Alas, we humans have only two distinct sexes capable of coupling for procreative purposes. Sure, we know many ways of enjoying that process, but reproductively we’re somewhat limited compared to many other living creatures.

How does this all sort out?

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Way back at the beginning of life on earth, some 3.5 billion years ago, those teeny tiny critters, the bacteria and viruses, cloned themselves. They reproduced by making more of the same with an occasional merger between two individuals in exchange of some particular ingredients, but that was a rather random process. Sure, mutations happened because of spontaneous alterations in the blue-printing molecules, but most of those changes did not survive. The rare good ones did, but that kind of evolution took a very long time. After about 2.3 billion years of trials and errors, Mother Nature worked out the complicated process of sexual reproduction as a better, more controlled way for living creatures to evolve in harmony with ever changing environments. Needing two times the energy of fission by cloning, sexual procreation comes at a cost, but its ubiquity indicates worth.

Sexual attractants, the molecules of passion and pleasure, provide motivation for the fertilizing act. Little is known of their nature, yet they play a strong role in the kind of procreation that provides a vast variety of offspring capable of fitting into Nature’s many niches.

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Mother Nature’s Kama Sutra, Part 2

KSBlogImage2Female worker bees find their food in the nectar of flowering plants. I see them flitting flower to flower sucking zealously. Most flowers have both male and female elements, leading us to think they can fertilize themselves. Mother Nature, however, blocked that mechanism in many specimens by superimposing a complicated incompatibility system to prevent the male pollen from getting to the female ovary. The only way these plants can complete the sexual act is by cross-fertilization following the matching rules of coupling between molecules with the required characteristics. The bottom line? Such plants cannot self-fertilize but can successfully fertilize most other members of the species, thus achieving outbreeding with a mix of genomes in successive generations.

Gregor Mendel, the father of inheritance—bee keeper, gardener, and monk—wanted to know how discernable traits are passed on from one generation to the next. Fortuitously, he first chose peas rather than bees for study. He cross-bred, by taking pollen from one known parent and depositing it on the tip of the tube leading to the bulbous female ovary of another. By scoring expression of certain parental traits, such as flower color and peapod shape, in the offspring of these crosses, he showed that defined characteristics of each parent were passed on from one generation to the next. Mendel tried working with bees for comparable studies. Alas the data from bees did not jibe with those of peas, due to the then unknown, unorthodox ways of sexual reproduction in bees.

Filled with the fragrance of pretty spring flowers, I turn again to that lily-padded frog pond and think of smaller creatures hidden therein—the microscopic fungi and algae. I pause to ponder the possible presence of tiny swimming spores coming from a little fresh water mold called Achlya ambisexualis, the subject of my master’s thesis many years ago. I and my mentor, John (Red) Raper fell in love while sampling small ponds in the hinterlands around Chicago to make collections of this wee critter for study back in the lab. We nurtured the spores on freshly cut hemp seeds and watched them develop into full-grown colonies of threadlike cells called hyphae. We paired the grownup colonies to look for evidence of mating.

Achlya ambisexualis is aptly named. It goes frogs, birds, fish, bees, and peas one better. It can be either male or female depending upon the partner it happens to meet. A supreme opportunist, this little mold spends no energy making fertilizing organs before they are needed. If you were one of its members, you could go either way depending upon the relative sexuality of the nearest possible partner. You could behave as male if your neighbor bears stronger female tendencies than you and vice versa.

Let’s say your male potential is stronger than that of your neighbor. She behaves as female and initiates the dalliance by sending you a signal to develop long finger-like appendages in readiness for genomic delivery. Then, and only then, do you release a message in response, telling that female to make her little nucleated egg sacks in order to receive your nuclei. She, in turn, signals your fertilizing elements hither to deliver your genes to hers within the encapsulated eggs. Voila!

My thesis aimed towards concentrating enough of a strong female’s message to determine its nature. I failed in this, but others succeeded by using better, more modern techniques. Amazingly, these later investigators defined the attracting signals of both sexes as two different steroid molecules resembling human sex hormones. The regulating genes remain unknown.

My love of the fungi persists from that time.

Moving on to the fringe of the woods, I  spot a light brown, dome-shaped mushroom hanging from a white birch tree. It must be Polyporus betulinus, a fungus studied by friend Abe Flexer, a fellow researcher in Red Raper’s lab. Abe discovered its sex life and found two sexes back in the nineteen seventies, but later investigators found more—as many as 33. How can that be?

KSBlogImage1Walking further, with mushrooms on my mind, I find a group of fan-shaped forms anchored to a log half-rotted. I kneel up close and cock my head. Each resembles a scallop shell, small as a fingernail, with irregular ridges of spore-bearing gills scoring the concave underside. It is Schizophyllum commune, my favorite mushroom-bearing fungus, with not just three dozen sexes but thousands.

Mother Nature’s Kama Sutra, Part 1

birdBirds do it. bees do it. frogs, plants, fungi do it. Most living creatures have sex.

Why do they do that?

Sexual reproduction grabs the fastest path to long-term survival in an ever changing world. It takes energy, but going through that tangled process of mixing genetic material  from one generation to the next is worth the effort. It is the most efficient way to make a mixed array of DNA blueprints for facing life’s uncertainties. It also accelerates repair of damaged DNA which can range as high as twenty to sixty thousand injuries per day in mammalian cells such as ours.

This much I’ve learned from a life-long interest in biology focused on genetics.

But how is reproduction by means of sex accomplished?

These thoughts ran through my mind as I wandered through a Vermont woodland one fine spring day.

We humans know something of how sex works for us to spawn the next generation—basically, XX chromosomes for females versus XY chromosomes for males, with the accompanying paraphernalia. Male and female allure one another through sight, smell, taste, sound, and feel. Full attraction attained, male inserts penis into female vagina and delivers its genome packaged in sperm to join female genome in egg. Gender identity does not always match anatomical male-female differences. Same-sex allurement happens but cannot lead to procreation—we cannot reproduce our entire being by cloning, not naturally.

But ours is not the only way. What of nature’s other creatures?

frogsWalking by a lily-padded pond, I saw a tiny speckled frog perched atop a floating log. What’s with frogs? How do they strategize sex? I’ve heard their nighttime courtship calls. I  know they hatch as tadpoles from fertilized eggs in water and develop from tadpoles to full grown adults. But unlike mammals, frogs can have different kinds of sex chromosomes: some species have XX females and XY males, others have more homologous chromosomes called ZW and ZZ, and some of these little hoppers, such as the African reed frog, can defy the differential chromosome rule by switching sex when timely. Confronted with a shortage of males, females can turn into males and redress the balance. If need be, males can switch the other way around. Their sex chromosomes combine both male and female potential. Such frogs are born with both ovarian and testicular tissue, but only one type develops to function at any one time. No one yet knows just how these changes are perpetrated, but some kind of long distance signaling is probably involved.

Some fish do likewise, just to balance the sexes.

Look up to the sky, the birds up there. They have two sexes, but, unlike mammals, it’s the female who carries two different sex chromosomes (ZW) while the male has identical ones (ZZ). Through fertilization, genetic union, and the special two-step process of genetic recombination called meiosis, female determines the sexual identity of offspring.

beesBees bustle within the fragrance of spring flowers. For these busy little buzzers, only females develop from eggs fertilized by sperm. Males, oddly enough, develop from unfertilized eggs that are derived either from the queen bee or from a rather rare so-called laying worker bee. Thus, a male genome, with just one set of chromosomes coming from a  female egg, is half the value of a new born female with two sets of chromosomes, one from the female parent plus one from the male parent. The doubly endowed females go out and work for a living; the males are drones who can’t even sting or forage. Being fed by worker females, a drone’s purpose in life is to fertilize some of the queen’s eggs—whereupon he expires in the act, leaving part of his innards behind. Usually a hive generates just one queen by nurturing a selected female with a special diet of royal jelly the first two weeks of life. This special feeding, denied to ordinary workers, is necessary for female organ development.

Working female bees gather food for the colony. They are the ones who sting. I wonder why, since death ensues thereafter. Perhaps it is a sacrificial act in protection of the hive. Alas, those female workers produce only male offspring. It is the queen of the lot who makes more females. She must stay healthy to keep the whole colony replenished with a proper gender balance.

My brother kept bees. Sometimes the queen escaped its hive leading the colony elsewhere. If those renegades settled on a tractable bush nearby, I’d cover up in overalls, netted hat and gloves, give that bush a shaking, dislodge them all into a wide-mouth container, close the lid, then carry them back to my brother’s hive for the fee of fifty cents. I did not get stung, nor did I ever earn much.

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*Excerpt from an essay published in The Best of  the Burlington Writers Workshop, 2016

All Animals Care

sea lion pup

Dogs, cats, even rats, can bond with human animals and come to care about us. But what about the wild ones?

While recently watching naturalist Joe Hutto, on Public Television’s Nature program, commune with wild mule deer, I thought of the time I sat alone on a volcanic island of the Galapagos as little lizards, Marine Iguanas, scurried linearly close by, and walloping sea lions stopped to lick my toes. It all seemed like a friendly greeting.

Joe Hutto spent a couple of years relating to a herd of mule deer on his land in the Wind River Region of Wyoming, and those deer came to trust him, even care for him. The head of the herd, he named Ragtag, cared so much she even licked his cheek in tenderness. When Ragtag died the whole herd visibly mourned. I was moved to tears when Joe Hutto found Ragtag’s orphaned faun, Molly, lying helplessly hungry without her mother. He nursed her to maturity and she became his constant friend.

Then I thought of a mother sea lion on the beach of another Galapagos Island who had just given birth to a still-born pup. That mother licked her baby for several minutes trying to restore life—to no avail. She then spent all her energy nudging that inert babe to the ocean’s edge and let it float out to the sea. No member of her herd came to offer condolences, even those nearby. None even came by out of curiosity, except a yearling offspring of that sad mother, who stood by and stared and stared.

Science: An Ongoing Detective Story

A woman scientist at the 29th Fungal Genetics Conference held at the Asilomar Conference Center in Pacific Grove, California, in March 2017, sponsored by the Genetics Society of America. I gave the Fungal Conference Perkins/Metzenberg Lecture in 1993, and I am pleased to see such growth in the field and the rise of women in science.

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I’ve not been at the bench in science for over ten years. While since devoting my time to a more sedentary, different profession as writer of memoirs and family sagas (www.cardyraper.com), I’m still fascinated by what’s going on in science, especially genetics.

Last month I escaped a 20-inch snowfall in Burlington, VT, to attend the twenty-ninth Fungal Genetics Conference at Asilomar, CA, on beautiful Monterey Bay. I went to just listen and learn. And this is what I learned:   1) Young folks give better talks than we old folks of the past. 2) New investigative tools allow these youngsters to find out more in two months than we old fogies could have done in years. 3) Women have ascended to at  least half the numbers, maybe more, of scientists in this field.  4) The science of genetics holds more unforeseen mysteries than ever!

Ha, we thought DNA was the absolute blueprint of how living creatures look, behave, and reproduce—not so. RNA (an evolutionary precedent of DNA) and proteins (the products of a special kind of RNA that translates the DNA message) have a lot to say. What’s more, environment shapes their function! A whole new field of epigenetics is taking off.

I used to think we had to wait for mutations in the DNA to adapt to a changing environment, but now we know it’s possible to adapt through small RNAs that alter expression of the genome.

If I had another life to live, I’d go for epigenetics as a master detective.

Art and Science

unnamedRed Raper and I produced an artist daughter, Linda Carlene Raper. L. Carlene presented me with the poster pictured. It is a photo of a work of art she surprised me with on my 49th birthday in 1974, when I was working with Red on the sex life of Agaricus bisporus.
Campbell Soup Company had provided a grant for Red and me to find out whether or not the mushroom used in their famous mushroom soup could be improved by breeding. Pleased, proud, and amused, we posted said poster on our laboratory wall at Harvard . Two days later, the poster went missing. Oh No! I promptly fixed a note to that blank spot:  “Whosoever took this work of art, please return it. It cannot possibly mean more to you than it does to me.” The thief never responded. What you see above is a photo taken the day of hanging.
As for the research project depicted, we found out that that mushroom does have a sex life, but all it does is fertilize itself–what good is that, I ask, if you can’t mix different genomes from different places? Well, using fancy molecular techniques, the system can be manipulated to cross breed, but not easily. Such research continues in other labs.
I had thought that Andy Warhol-like image was gone forever, but L. Carlene surprised me on my recent ninetieth birthday by digging its photo out of the archives and mounting it on a 2×3 foot poster board. It hangs in my hallway today.
Art meets science again.

An Incomparable Feeling

iguanaAmong many great moments of my life—the rush of first love, the birth of two healthy babies, a breakthrough scientific discovery—one of the best was feeling as one with other animals on a beach in the Galapagos. I sailed there with a small group of active thrill-seekers who could hike and climb with gusto. But my bum ankle, recently busted while skiing downhill, held me back. I sat alone on the beach of one of those islands while all others in the group hiked a volcanic mountain. Relaxing, eyes closed midst the soothing sounds and smells of ocean waves, I felt something stirring, licking my toes. Looking down, I found a cuddly young sea lion seemingly greeting me as one of them while a host of iguana marched past paying me no mind. Then three feet to my left, in a low lying bush, a nest of lava gull chicks squawked a greeting to their parent bearing food.

I was one of them—just another species.