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In this episode of Tiny Show and Tell Us, we hear from a listener who has Marfan syndrome and dive into the complexities of the disease. Then we talk about pathogens that eat � or infiltrate! � plant DNA.

Transcript of this Episode

Deboki Chakravarti:ÌýWelcome to Tiny Show and Tell Us, the bonus series where you write in with your favorite science news or factoid, and we read your email aloud and then dive deeper. I'm Deboki Chakravarti, and I'm here with my co-host, Sam Jones.

Sam Jones:ÌýLast time we talked about bioluminescence and anesthesia, because we do it all on Tiny Matters.

Deboki Chakravarti:ÌýWe even talked about Real Housewives.

Sam Jones:ÌýThat's true. You never know what you're going to get, and we also have a really great bonus episode for you today, so before we kick things off, we want to say thank you to Tien Nguyen for doing the research for this episode. A reminder that we are always looking for you to write to us to be featured in one of these episodes, so you can emailÌýtinymatters@acs.orgÌýor you can fill out the form that's linked in the episode description. Alrighty. Let's hop into it. Deboki, you want to go first this time, right?

Deboki Chakravarti:ÌýRight. I will go first.

Sam Jones:Ìý·¡³æ³¦±ð±ô±ô±ð²Ô³Ù.

Deboki Chakravarti:ÌýSo, I have an email from listener Benjiro who says, "When I was about 13 years old, I got diagnosed with Marfan syndrome, and I remember being told it was a connective tissue disorder, and learning how one defective protein can affect so many seemingly different things in your body. Connective tissue is found in muscles, ligaments, bones, skin, eyes, organs, and what surprised me the most, blood. Living with this disease has given me a new perspective on all the intricacies that occur within the body and just how precise everything is.â€� Yeah. I think that's a really interesting perspective on it, because that is wild to have gone more into this and realize, "Yeah. This all comes down to one protein."

Sam Jones:Ìý³Û±ð²¹³ó. It just makes me think too, in the episode we did on hemophilia a little while back, it's like one change in one nucleotide, in one gene, and then someone has hemophilia. It's pretty wild that way.

Deboki Chakravarti:ÌýRight, and so for Marfan syndrome, that protein is called fibrillin-I, and so this helps mix the fibers that are in our connective tissue, and so the gene that encodes this protein is called FBN-I, and so what will usually happen is that the person with Marfan syndrome, they'll inherit probably one normal copy from one parent, but probably get an abnormal copy from another parent, meaning that there's some kind of mutation that's changing the amount of fibrillin-I getting made. The caveat, though, is that there are roughly a quarter people with Marfan syndrome who have parents who don't have Marfan syndrome, so it can also happen differently.

Sam Jones:ÌýSo it's a random mutation that just pops up, and it's not genetically passed on.

Deboki Chakravarti:ÌýYeah, which is also something I think that came up in our hemophilia episode.

Sam Jones:ÌýYeah, yeah.

Deboki Chakravarti:ÌýYeah, and so this leads to issues in the connective tissue that help out our bones and muscles and tissues and everything else. It can lead to bones actually growing longer than usual, which I thought was really interesting. I wouldn't have expected that, but that is one of the potential effects of it, but it can also be really tough to diagnose, because the symptoms are pretty varied. Also, there are other connective tissue disorders that have the same symptoms. The diagnosis is usually based on a combination of having the symptoms, but also having that family history. There are a few tests that can be used to confirm Marfan syndrome, like an echocardiogram, which will look at the motion of the heart. There are also eye tests and genetic tests.

There isn't a cure yet for Marfan syndrome, but there are treatments to deal with some of the issues that can come up. So for example, someone with Marfan syndrome might take drugs to lower their blood pressure, so that actually will help to keep their aorta from getting too big and also prevent it from potentially rupturing. You can get glasses to help with stuff in the eye. You can also get surgery to repair the aorta. Apparently, retinas can come loose, so there are also surgeries to help with that, and then treatments for scoliosis, or I guess another thing that can happen is the breast bone can either start protruding or sinking, and so there are actually different ways to kind of correct that as well. It all goes down to that one protein. It's so crazy.

Sam Jones:ÌýYeah, and I really didn't. I feel like Marfan syndrome is definitely underappreciated genetic disorder, I would say, to some degree, at least. I think, Benjiro, thank you so much for sharing your story with us and making us look into it, because I think that a lot of times in science, there are some conditions or disorders that just don't get enough attention or people don't really know about, and I think this seems like an important one to just be aware of and understand, because of course it's affecting people. It might even affect some people, we have no idea it's affecting them.

Deboki Chakravarti:ÌýRight.

Sam Jones:ÌýYeah. Okay, so my Tiny Show and Tell Us today is from listener, Nick. Nick wrote in saying, "Some plant pathogens may eat DNA as a source of micronutrients that they cannot make themselves."

Deboki Chakravarti:ÌýWhat?

Sam Jones:ÌýWhich I thought was really cool. I know. I had no idea.

Deboki Chakravarti:ÌýThey're just like, "Num, num, num, num," to the DNA.

Sam Jones:ÌýYeah, exactly. So I don't think of DNA having any nutritional value.

Deboki Chakravarti:ÌýRight.

Sam Jones:ÌýBecause yeah, it's DNA, but of course it does. It's made up of a sugar backbone. It has other molecules. I think we're so trained to think of macronutrients, so this is very interesting. Let's talk about some pathogens that may eat DNA. One of them is the bacterium E. coli, which I think many of us know. I think most people know the name E. coli, because it's like that's the outbreak. That's the thing that's making people sick.

So E. coli, I guess they like to munch on the carbon and nitrogen in DNA, and they can also digest long strands of DNA, and so I have this very silly image of an E. coli eating DNA like spaghetti, twirling it around a fork and eating it. Yeah, it's not good to bring personality to bacteria, but anyhow, so Nick did link to a study for us, and the pathogen that's mentioned in that study is called Candidatus Liberibacter, so Candidatus Liberibacter is a genus of bacteria that is phloem-limited. It's called a phloem-limited plant pathogen, which I had no idea what that meant, but I very quickly realized it was pretty straightforward. It just means that it hangs out and replicates in a plant's phloem, which I don't think I've thought about since biology in high school.

Deboki Chakravarti:Ìý¸é¾±²µ³ó³Ù.

Sam Jones:ÌýPhloem is this vascular tissue in plants that transports nutrients, and so this bacterium, hanging out there, can be really devastating. It also seems like it is an insect transmitted bacteria, so the study that Nick sent along really focuses on structures that allow this pathogen to move around in the phloem and to take up the DNA, but it does get into the weeds pretty quick, but Tien did find another plant pathogen that I want to talk about, also a bacteria, called Agrobacterium tumefaciens, I believe is how it's pronounced. So, it's found in soil, and instead of just eating DNA, what it does is it'll actually transfer a segment of its DNA into plant cells. Yeah, so to my knowledge, it's not eating the plant's DNA, but it's manipulating it.

So, I know this is a little bit different, but I just thought that it was really cool. Really cool. So, by transferring a segment of its DNA, the Agrobacterium tumefaciens tricks the plant into feeding it, which I'm going to explain. That's great for the pathogen, but the plant suffers because the bacteria causes something called crown gall disease, where these tumor-like growths called galls are going to pop up on the roots, sometimes the branches of the plants. They can stunt the plant's growth and also cause rotting and other issues, and I feel like I've seen this before on trees, where you feel like you see this big kind of tumor somewhere on the trees, somewhere on a branch or something, or at the bottom near where the roots are coming up. So, it could be that, but there could also be a million different things I don't know about in plants that could be causing that.

So, my question then was like, how does this whole DNA transfer thing work? So, when Agrobacterium tumefaciens comes in contact with a plant, it releases chemicals that allow it to attach, and then that switches on. We could go into days worth of detail. I'm going to keep it not surface level, but I'm not going to go so deep, but I will link to something, so if you want to go nuts on this, you can. So then, that switches on specific genes that code for protein called VIRD-II or V-I-R-D-II, that actually then cuts the bit of DNA out of the plasmid in the bacterium. That little cut piece is called transfer DNA or T-DNA, so at the same time, so you have this protein that's activated that does the cutting, but then there are other genes in the bacterium that are activated that code for proteins, that create what kind of looks like a needle that sticks out of the bacterium into the plant cell.

Deboki Chakravarti:Ìý°Â´Ç·É.

Sam Jones:ÌýAnd that is what the T-DNA is injected through, so it's injected through this protein needle, I'm calling it, into the plant cell, where it makes its way into the plant's nucleus, where the plant's DNA is found. And so, from there, then the bacterium's little piece of DNA, the T-DNA is inserted into the plant cell's DNA, and it codes for hormones and other proteins that will make the plant cells replicate. And so, the replication of cells can lead to those large tumor-looking galls, but also the DNA is coding for chemicals that the plant wouldn't normally make. There's this Frontiers for Young Minds article that Tian found, where they say, "When the agrobacterium inserts, its T-DNA instructions into the plant DNA, it is basically sharing a favorite family recipe with the plant." I kind of love that. I know it's diabolical, because this bacterium is bringing disease into a plant, manipulating it for its own use but I'm like, "Oh. It's sharing its family recipes."

Deboki Chakravarti:Ìý³Û±ð²¹³ó.

Sam Jones:ÌýYeah, so I thought this was very interesting, and I know it's slightly off-topic for what was sent in, but I was like, "Let's not just talk about eating DNA. Let's talk about manipulating DNA," and so, really at the end of the day, this bacterium is creating a genetically modified organism, the plant, to suit its needs. When scientists first realized that it could do this in the 1980s, they began using it, and by the late 90s in the United States, there were over 35 genetically engineered plants that were created using this bacterium, and then were being used in commercial production, which is pretty cool. Things like potatoes, tomatoes, and corn, so not only is it doing this in nature, but I think that's a lot of times what's really cool or interesting about science, where it's like, "Okay, so we have this natural process. Is there a way we could use this to make our foods more resistant to, say, insects, drought, or all of these other things, without spraying them like crazy with pesticides or something like that?" So, I think bacteria are amazing.

Deboki Chakravarti:ÌýThey're pretty wild. Yeah.

Sam Jones:ÌýDiabolically amazing.

Deboki Chakravarti:Ìý³Û±ð²¹³ó. That made me think about how many of our genetic engineering tools are really just derived from bacteria, like CRISPR, obviously, and then-

Sam Jones:ÌýLike, all of it.

Deboki Chakravarti: Basically, all of it.

Sam Jones:ÌýAlmost all of it.

Deboki Chakravarti:ÌýThe original genetic engineers.

Sam Jones:ÌýYeah, like bacteria, viruses. We're just looking at pathogens and being like, "How do you guys get into stuff and change it? Because we want to do that too." Thanks to Nick and Benjiro for submitting to Tiny Show and Tell Us, a bonus episode from Tiny Matters created by the American Chemical Öйú365betÖÐÎĹÙÍø and produced by Multitude, and a big thank you to science journalist Tien Nguyen, who did research for this episode.

Deboki Chakravarti:ÌýYou can send us an email to be featured in a future tiny show and tell us episode atÌýTiny Matters at acs.org, or you can fill out the form that's linked in the episode description. We'll see you next time.

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