18 January 2011

Fungi Are Gender Benders

One of the most fascinating discoveries that I made as a 9th grader sitting in the high school greenhouse taking biology at Talawanda High School was that there are some kinds of living things that have reproductive cycles far more complicated than that of simply dividing cloning cells, two gender system vertebrates, and multi-stage life cycle creatures like frogs (who early on look like fish called tadpoles) and butterflies (if you mother didn't tell you about the butterfly life cycle, you must have been an exceptionally beautiful and graceful child).

A received an echo of that moment again reading "The Host" by Stephenie Meyer, a little while ago, that has a story within a story sketch about an alien life form with a more complicated than two gender reproductive system.

Among the only reproductive concepts that have rivalled this revelation since then, most of which I have encountered first in science fiction, are the notion that viruses can change genomes, the discovery that some kinds of vertebrates can have virgin births in certain circumstances, the discovery that one can have mixed paternity twins (or even more amazingly mixed DNA individuals), the discovery that we are probably part Neanderthal, and the notion that ancient DNA might be used to create living versions of extinct creatures a la Jurassic Park: Japan has set out to resurrect the Mammoth by 2015.

Then, I came across a post at Replicated Typo today that recalled that moment for me. You see, some of the most complex reproductive systems of any living things are fungi.

Their reproductive mechanisms is rather unexpectedly complex, in that the normal conventions of sex do not apply. Not all fungi reproduce sexually, and many are isogamous, meaning that their gametes look the same and differ only in certain alleles in certain areas called mating-type regions. Some fungi only have two mating types, which would give the illusion of being like animal genders. However, others, like Schizophyllum commune, have over ten thousand (although these interact in an odd way, such that they’re only productive if the mating regions are highly compatible (Uyenoyama 2005)).

Some fungi are homothallic, meaning that self-mating and reproduction is possible. This means that a spore has within it two dissimilar nuclei, ready to mate – the button mushroom apparently does this (yes, the kind you buy in a supermarket.) Heterothallic fungi, on the other hand, merely needs to find another fungi that isn’t the same mating type – which is pretty easy, if there are hundreds of options. Other types of fungi can’t reproduce together, but can vegetatively blend together to share resources, interestingly enough. Think of mind-melding, like Spock. Alternatively, think of mycelia fusing together to share resources.

In short, the system is ridiculously confusing, and not at all like the simple bipolar genders of, say, humans (if we take the canonical view of human gender, meaning only two.) I’m still trying to find adequate research on the origins of this sort of system. Understandably, it’s difficult. Mycologists agree:

“The molecular genetical studies of the past ten years have revealed a genetic fluidity in fungi that could never have been imagined. Transposons and other mobile elements can switch the mating types of fungi and cause chromosonal rearrangements. Deletions of mitochondrial genes can accumulate as either symptomless plasmids or as disruptive elements leading to cellular senescence…[in summary,] many aspects of the genetic fluidity of fungi remain to be resolved, and probably many more remain to be discovered.” (Deacon, 1997: pg. 157)

There is a linguistic angle in the original post on gender agreement in language, but quite frankly, it doesn't interest me. But, amazing complex versions of sex do. What benefit do mushrooms receive from their more elaborate forms of reproduction? Are there downsides to it? How does it work? What are the general patterns of the diversity in reproductive arrangement in fungi?

I'm already familiar to some extent with fungi weirdness. In some ways they are more like animals (e.g. they don't generally produce their own food through photosynthesis). In other ways they are more like plants (e.g. they are generally sessile). Some fungi produces remarkable neurological responses. Fungi colonies have also proven to be far more elaborate multi-species ecosystems than most people had realized with lots of undiscovered complexity. But, complex reproductive mechanisms adds a whole new dimension to the brew. And, in an age where we may be nearing the "end of science" in physics and inorganic chemistry, seriously unexplored territory in biology is the place to learn new things whose utility was not previously recognized. Also, because researching fungi involves far less expensive laboratory equipment and conditions and staffing requirements than many other areas of science, while having an unusually large share of unanswered questions, it presents that possibility of pretty small scale scientific pioneers out of anywhere discovering cool new things.

More deeply, and more to the point of the linguistics post cited, how does being forced to look at issues of gender in a far more generalized and complex way than we are now aware that human neurodiversity involves in sometimes rare permutations (male, female; gay, bi, straight; butch-femme; cis and trans gender; dimensions of gender; archaic human-modern human hybrids, etc.) enlighten our thinking about the combinations and interactions encountered by humans.

The details of how fungi do it in interesting systems will have to wait for future posts. But, I wanted to note some access points to start looking into again before the thought left me.

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