Now we're in the office that's attached to my lab. And we're going to take a few minutes just to talk about the research that's going on, and connect it, if possible, to the subjects that we learned about during the course. Now if you remember, we talked about how a seedling grows in the dark and the light. That a seedling that's grown in the dark, it has a long hypocotyl, and its leaves are closed and its elongated. Whereas, one that grows in the light is short, and its, and its, and its called a leadance, its first leaves are open and expanded. We also mentioned how this type of, of a seedling, one that's grown in the light, will continue on into sexual development, seeds, and flowering, while this one arrests. Well, the question that interested me 20 years ago, when I started my post doc was, how does, how do plants use light as a developmental signal? because we know that it's enough to, you know, give this plant a few seconds of light, and then we will get photomorphogenesis. Okay. So work that had been done in other labs showed that it was actually sunlight coming through the photoreceptors, such as, from phytochrome or from cryptochrome, so either the red light or the blue light, which then converge to allow plants to go through photomorphogenesis. And I want to know is, how are plants differentiating between dark and light? And the way we did this was genetic. We found mutant plants that when they were in the dark, they were still short and that open cotyledons, even though, that's a moon there. Okay, see my, my, my drawing abilities isn't the best in the world. Even though, they were in the dark. These seedlings in the dark look just like normal seedlings in the light, okay? So the question was what was wrong with these seedlings? What we discovered was that was a group of eight proteins, that I'll call [NOISE] the CSN, the compromising signalasome is a group of eight proteins. And what do we discover? That the role of the CSN is to repress. This is a symbol meaning repress. It represses photomorphogenesis in the light, in the dark. Excuse me. So under normal dark conditions, the COP9 signalosome inhibits this. And we get this type of growing. What happens is that the light signals coming from phytochrome and cryptochrome impinge on the COP9 signalosome. But what's their function? Their function is negative. They inhibit the inhibitor, so if the light signals inhibit the COP9 signalosome that means as your light conditions we get further more photogenesis, and here is how we could see how the genetic works. Because what's happens if I have the mutant in the COP9 signalosome, that a mutant in one of these eight sub units so that it doesn't work, then we never have the repression, doesn't matter if it's in the light or the dark, there's no repression so we'll always get photomorphogensis. Now here comes the, what I think is the most interesting part of all. So, on the one hand we identified a negative regulator of photomorphogenesis that's downstream of the, of the photoreceptors from phytochrome and cryptochrome. This is something that's very specific for plants. I also talked about this in one of the lectures. Opening our leaves in the light. Opening the leaves in the light is a plant specific process. But when I clone the genes that enclose the COP9 signalosome, I found that the CSN is not only found in arabodopsis, it's found fruit flies. And it's also found in humans. So of course the question is, why do fruit flies, and why do humans, have a COP9 signalosome? Now, I'm just going to take one more piece of data to show you, or to, to describe to you. So we've done similar experiments now using fruit flies as a model system because I'm a big believer that through genetic analysis we can understand the basic processes. So what have we done? We've taken fruit flies and I'll, how do I draw a fly, okay, there's a wing, and there's its head, okay. So this is my rough version of a fruit fly. Before the fruit fly, it had what's called a larva, it's like a little worm, and we made mutations in the COP9 signalosome zone in the fruit fly, and now you look at what phenotypes they have. And when we looked in the larva of the CSN mutants, there's no COP9 signalosome in these mutants. What we saw is that they had black dots in them, and when you dissect these black dots, this is a type of fly leukemia. In other words, the COP9 signalosome in flies affects cell division. It affects how the cells are dividing and how they're differentiating. When there's a mutation, the cell division doesn't occur in the right way, you get too much cell division, but the cells aren't formed in the proper way and you get leukemia. We actually now know that the COP9 signalosome is involved in a number of human cancers. In Arabidopsis, of course there's no such thing as cancer. There's no leukemia. But there we see the phenotype in photomorphogenesis, in how the plant responds to light. So on a very basic level, what we see is that a mutation in the COP9 signalosome affects the way a plant responds to the external environment. because what did we say, what majorly regulates a plant's development? The external environment. Because they're rooted, they have to be aware of what's going on around us. What regulates development in an animal? The internal environment. The internal clock. And so the phenotypes are internal defense. Now let's go out into the lab where you can see what some of the students are doing on experiments today. Alright, so let's see what's going on in this part of the lab. here we have a project that's going on. This is Manelli she's a masters student in the lab. >> Hi >> And what she has here is a Arabidopsis that are growing on plates. And, what we're actually doing, >> This one's better. >> This one's better? Thank you. Are looking for mutants that, whose roots are longer under condition, than the wild type r, and so what Manelli has actually been doing for two years, is screening thousands and thousands. >> Yeah. >> And thousands of these plants, in order to find the mutants. Okay? So over here, this is Ela. Ela is a PhD student in the lab, and right now Ela is not working on a wet experiment. She's doing a dry experiment. A lot of our time is spent using computers, and what she's doing is she's analyzing data of how genes are transcribed, how they're turned on under different conditions, which interests her in the lab. So she did the wet experiment a few weeks ago, and now a lot of her work is spent analyzing the data itself. Okay, let's see what's going on in the lab right now. this is the, actually the, more of the office part of the lab, where we do the administration. so now I've reached Muti ben, bench. Muti is a PhD student and as you can see, she doesn't work with plants. Muti works with fruit flies. These are Drosophila, that are working around. And what her research entails is trying to understand how the COP9 signalosome, the CSN, influences gene transcription in these lovely little organisms. So she works both with the flies and she also works with cells of the flies, which we grow in those things.