Orb weaver spider glue properties evolve faster than their glue genes | Hacker News Reader

Orb weaver spider glue properties evolve faster than their glue genes

phys.org

36 pointswglb24 comments

What's not mentioned in this lay-man summary, but is mentioned in the original article is glycosylation.

https://www.frontiersin.org/articles/10.3389/fevo.2023.10994...

Glycosylation is a post-translational modification that affects dramatic impact on protein function, especially their "stickiness."

There are distinct genes which are responsible for encoding glycosyl transferases, which "decorate" the proteins after they are made. The fact that whoever wrote this article thinks these are not "glue genes" is a fallacy of composition.

https://en.wikipedia.org/wiki/Fallacy_of_composition

The article mentions that the proteins in question are highly glycosylated and concludes "Divergence in material properties likely also involves selective gene expression, post translational protein modifications, and differences in the rates of extrusion of constituent glue proteins."

Therefore, the title is click-bait.

Since I happen to know these species: the spider pictured at the top of the article is an Argiope bruennichi (Wasp Spider), a European species which closely resembles A. trifasciata (Banded Garden Spider, one of the two species in the study).

For those who would prefer a link to the original paper instead of coverage of that paper: https://www.frontiersin.org/articles/10.3389/fevo.2023.10994...

I didn't read the original article, but this write up does not explain the title at all. Evolution works at the genetic level does it not? What is natural selection modifying if it is not the genes?

Same question. I could imagine a variety of answers, I don't this it's exactly impossible, but yeah, the actual answer is the interesting thing the title had me wanting, and not getting here!

Or I wonder if this popular write-up article just got it's title wrong?

Someone on here recommended a book called "Wetware: A Computer in Every Living Cell" and it goes into detail but at a fairly layman level explaining how stuff like this works at the biochemical level. Basically we have genes that code for pieces of proteins and those pieces can be combined in millions of different ways to form unique proteins. Feedback systems based on proteins turn individual genes on and off to encourage the production of effective proteins. Essentially we have the ability to evolve and adapt at the protein level without any modifications to our genes.

Honestly reading that book really opened my eyes to how complex this stuff really is. Biology is unbelievably robust and flexible well beyond the basic model of evolution that we are taught takes places at the genetic level.

Thanks -- I will hopefully have time to read more. I don't understand how the turning on and off of genes is passed to the offspring.

Natural selection is the sieve, not the modifier.

That quibble aside, there are also epigenetics to consider.

OK -- now I am more confused. Selection is a sieve that "selects" the "best fit" which, in the long run, brings modification. Epigenetics is just the manifestation of gene expression under different environmental conditions. Still, in the final overview, it is the genes that are passed on to the offspring. What else is there to inherit?

> which, in the long run, brings modification.

Not quite.

It's the part that filters the ideas, not the part that generates them to begin with.

For that you need a source of change.

It doesn't even need to be external; DNA is automutagenic (read up on transposons).

There's also homologous recombination that exchanges the DNA between the copies of the same chromosome inherited from different parents (if this didn't happen, you couldn't inherit genes from multiple grandparents in a single chromosome).

https://en.wikipedia.org/wiki/Homologous_recombination#In_eu...

The two species share a lot of glue genes, and the properties of their silks differ due to other genes affecting things like the ratios of glue proteins in the silk. Those other genes evolved faster than the glue genes themselves.

The title is technically correct, though misleading.

I like to think of genes as keys on a piano. But the genome also includes the a lot of the musical score. You can get a lot of different songs with a finite set of keys played in different combinations and sequences and amplitudes.

In this picture, most of evolution wouldn't be changing the keys but changing the score.

Ummm, bad title. There is nothing here that suggests evolution of any sort.

TLDR; spider glue can be produced to work in different humidities by altering the ratio of proteins in it. No evolutionary mechanism is discussed at all.

in other news, "finger positioning properties evolve faster than finger genes?"

Doesn't seem too surprising that spiders can change their silk for varying conditions. It's part of their body, after all - they are going to be good at using it even in microscopically different ways.

The spiders haven't even been shown to change their silk in response to conditions. It's just two species of spiders each with their own silk recipe.

I guess physical.org also uses ChatGPT to generate random headlines..

The word "evolve" does not have such a narrow meaning outside of a specific technical context. From the paper:

The ability to selectively express different glue protein genes and/or to extrude their products at different rates provides a faster mechanism to evolve material properties than sequence evolution alone.

I disagree. Evolve has a general meaning that is widely understood, not just in a specific technical context.

The fact that a spider can selectively express different proteins to suit different conditions is no different to all the other ways a living body can selectively alter protein expression to suit different conditions. We would not describe those as evolution.

>We would not describe those as evolution.

What do you mean by "we"? Because I happen to have degrees in Genomics and Biology and I would definitely describe that as evolution.

You are correct, and I misunderstood what the article was saying. I just skimmed the paper itself.

I thought it was saying that spiders were simply adjusting the material properties of their glue in response to environmental conditions. This is not evolution.

The paper is saying that while the glue genes themselves are largely conserved, the material properties can vary by altering the ratios of protein which are expressed.

Presumably this ratio is controlled due to other faster evolving genes (although this is not proven by the paper as far as I can see). I'm not entirely sure if they ruled out whether spiders could in fact adjust their glue in response to changing environmental conditions.

Nowhere in the paper does it say that individual spiders are varying their silk composition in response to conditions. The selective expression of proteins is a difference between the two species studied, not between individuals within one species.

The title is technically correct: the two species share a lot of glue genes, and the properties of their silks differ due to other genes affecting things like the ratios of glue proteins in the silk, and those genes evolved faster than the glue genes themselves.

Correct, although I'm not sure if they proved that other genes were responsible for the variation, just that the glue genes were essentially the same between them.

I for one definitely go grab the shotgun everytime I hear that "the situation is rapidly evolving" on the news. Someone has to be ready to defend against all those mutants. /s

The article discusses the glue produced by orb web and cobweb weaving spiders in the Araneoidea superfamily. The glue is produced in specialized silk glands and is responsive to the environment. Researchers compared the glue of two spider species and found that both species had around 30 proteins contributing to the stickiness of the glue, but the number and relative contribution of each protein group differed between the two species.

The ability to selectively express different glue protein genes provides a faster mechanism to evolve material properties than sequence evolution alone.

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