Physcomitrella patens (physcomitrella moss)

This biweekly plant's info comes mainly from watching a YouTube video called: Magdalena Bezanilla (Dartmouth) 1: Understanding cell shape: Big insights from little plants. I wanted to understand the plant at a base level a bit more, and found that many of the academic papers I looked up were very specific to certain genes and functions. Not that this isn't interesting, but I'm still not at that level of understanding with genetics and especially proteins. So this post will be a bit of a detailed overview and my thoughts about this particular moss and why it seems to be really interesting.

Physcomitrella patens (p. patens moving forward) is one of those plants that has been identified as a model organism to study. Model organism to study usually means that it is easy to grow in the lab, has very specific responses to specific things we do to it, and usually grows fast. Plants as such are interesting because of their convenience to human scientists. Trying to study redwoods in this fashion would require that many human generations die before any real results could be extrapolated.

A quick overview of the lifecycle of this plant in particular. P. patens begins the lifecycle as a haploid spore. This means that the spore only has one set of chromosomes (human cells have 2 sets of chromosomes, from mom+dad). From this spore, protonemata, or filamentous tissues, begin to develop. Filament just means an extension, like wire or hair. You can kind of think of a strand of your hair as a filament.

The extending protonemata have 2 tissue types: 1) chloronemal tissue, which has lots of chloroplasts (the photosynthesis factories of plant cells, i.e. how plants get their food), and 2) caulonemal cells, which grow faster and have less chloroplasts. These extending protonemata become the "branches" of the moss. They can either continue to branch, or begin to bud.

If the cell begins to bud, then the bud is a predecessor to a leaf shoot. The leaf shoot can develop into what is known as the gametophore, where the apex (meaning the very end or top) of the gametophore is where the female and male sex organs develop on the plant.

The male organs of the plant contain flagellant sperm, which means the sperm have little flagella, tail like structures, to help them navigate (swim) to the eggs. Once the sperm make it to the female organs, you get fertilization. The fertilization is the only diploid part of this life cycle, diploid meaning male+female chromosomes each have sets. Fertilization will make the sporophyte, and the sporophyte undergoes meiosis (cell division that reduces the number of chromosomes by half, in turn creating 4 haploid cells distinct from the parent cell). The meiosis makes the haploid spore cells, and the process begins all over again.

P. patens has apical and subapical cell division, which means that for apical cell division, the plane of division is right in the center, i.e. the nucleus is in the center upon cell division. Subapical cell division means the plane of division is not in the exact center, i.e. the nucleus is on one side or the other when the cell begins dividing.

Apparently, p. patens also is a sturdy little organism. The video states you can literally blend the whole plant in a blender with water, and the cells will re-differentiate themselves to develop into protonemal cells again. Say WHAT! Imagine blending a human up, and expecting for any one cell to create another human again, not gonna happen. You can use a single p. patens cell to regenerate an entire plant again, amazing! The video says you need to put the cells with enzymes so the enzymes can digest the cell walls, and only the protoplasts, single cells, remain. The protoplasts can then be watched for regeneration. Pretty nifty stuff if you ask me.

The complete genome for p. patens has also been sequenced in its entirety, which means that when you're playing around with gene editing in this plant, there's a frame of reference to work off of when analyzing data. It's also handy because it is the only plant known (says the video) that undergoes efficient homologous recombination when transformed with a piece of DNA to be able to do very precise manipulations. Homologous what?

Think of a long string. On one end of the string there is STOP sign. On the other side of the string, there is another STOP sign. Everything in between those 2 stop signs are a genetic code that creates a protein. This protein can be thought of as little instructions taken to other parts of the organism. The proteins help perform important functions in the organism and have an array of uses. Now, with homologous recombination, this means that you can take out the piece of string in between the 2 STOP signs and replace it with another string of your choosing. When you do this, the protein coding region is gone, which would make this what is called a null allele, basically meaning that there is no more protein code, and this gene is now not functional. So in the lab, you can swap out these genes and make them null to determine how a plant is affected by the non-expression of this previous gene. Some genes are essential though, so if essential genes are swapped out, then the plant will die. You unfortunately can't regenerate a dead plant, at least not to my knowledge.

But wait, if homologous recombination is used, there are some challenges. This plant, along with many other organisms, has an ancient genome with lots of copies of the same gene, known as functional redundancy. So when swapping the piece of string between the 2 stop signs, a copy of that same gene will just come in to save the day. It's like having a lot of spare car keys to start a car. If one pair gets stolen, you just use another pair. If you have multiple pairs, there's going to have to be a ton of stealing before the keys no longer exist. This is a very smart survival technique in nature, but not very handy in the lab. So what to do? RNA interference of course.

RNA is not DNA. RNA plays an important role in gene expression however, and in this case can be used to shut off specific gene expression. RNA does not affect the genome at all, but it can affect the expression of genes. Depending on which gene you want to study in the plant, you can use RNA to degrade m-RNA (m for messenger meaning it takes instructions to other parts and helps with translation) or halt m-RNA altogether, so now a specific gene is not expressed within the entire organism. You then use these cells to regenerate the plant, and see how the phenotype (a fancy term for what something looks like) is affected when certain genes are switched off. Hence a model organism to study because of its convenience.

Moving on.

In p. patens, there is polarized cell expansion. Polarized just means there are poles, like north and south poles (but not exactly in this case) in which cell expansion occurs. In this case, polarized cell expansion means the expansion happens on one side of the cell. Vesicles (like little cases of stuff) are loaded with flexible cell wall material and are all pushed towards the cell apex, i.e. the tip of the cell as it's extending. This material is very flexible, so all the growth needs is turgor pressure (force that pushes plasma membrane against the cell wall) to expand. Since everywhere else in the cell, except for this apex tip, is not as flexible as the material in the tip, turgor pressure concentrates the growth in this area and the cell expands in a polarized (to one side) fashion. Imagine a water balloon in a cardboard tube. If you push against one side, the other side is going to expand on the opposite end of the cardboard tube, it's not going to expand the tube. Same general concept.

The video talks about how this expansion is regulated in the cell. It's through the protein actin. Actin is a monomeric protein that can dimerize and trimerize. What? Think of a molecule of actin as a lego block, monomeric. To dimerize, this lego block joins with another lego block of its kind, 2 lego blocks together dimerize. To trimerize, this lego block joins with 2 other lego blocks of the same kind, 3 lego blocks is a trimer. To dimerize and trimerize, it does not have to be the same lego block, but in the case of actin in p. patens regulating cell expansion, it is the same lego block of actin. These 3 lego blocks together, a trimer, are the base for creating a filament (remember, long strand) of actin. You can connect more lego blocks to both ends of this trimer to create a larger filament. 3 lego blocks connected to another group of 3 lego blocks creates a longer and longer filament of actin. If you find a protein that can bind to actin (say, one found in a drug that you can administer to the plant), then you can disrupt this process very specifically in order to see how this disruption (i.e. lack of gene expression by inhibiting a protein) affects the plant phenotype (what the plant looks like).

Actin is a major driver for this plant cell to grow. Without actin, the cell tip just swells, but does not extend. Remember the cardboard tube and balloon example. Say your trying to extend the water balloon to push out of the tube. You can press it at one end to extend it at the other to touch the wall or something. Now remove the cardboard tube, and try to do the same thing. The balloon kinda will move everywhere when you squeeze it, and it'll just swell and not extend. Similar concept in this cell with actin disruption. In a normal functioning plant, actin is the at the other end coming out of the tube, telling the balloon which direction it should be pushing towards.

Cortical actin (cortical meaning towards the walls and not concentrated on the tip) helps to guide cell expansion as well, but is not as concentrated as the actin located in the cell tip. The large actin concentration on the tip of the cell tells everything where it needs to be pushing towards to extend. Both of these processes have to occur for there to be rapid cell growth. It's kinds like the cortical actin tells the water balloon where the cardboard tube is, and the tip actin tells the water balloon which way it needs to extend.

This concludes my one video research into p. patens for now. Who knew a moss could be SO COOL!

Once I'm better versed in genetics and proteins, you can bet your ass I'll be studying the exact mechanics of what happens to cells when these processes are manipulated. For now, I'll keep my information general, as I still have quite a bit to learn.

References:

https://www.youtube.com/watch?v=_ZKC-18J6hY
http://www3.botany.ubc.ca/bryophyte/mossintro.html

Chionanthus Virginicus (White Fringetree)

Chionanthus virginicus or white fringetree is a plant that is endemic to the eastern United States, but more concentrated in the southeast. It also occurs in other parts, like the northeastern part of the U.S., but is not originally native to that area. It's fascinating how plants can be introduced to certain areas, and thrive. It's almost like their just like humans in having a presence all over the planet (imagine that). Of course, plants as a species will even have their extremes, like it is likely you would never see this plant occurring naturally in a desert region, nor would this plant planted in the desert wild likely survive. This doesn't mean you won't see it in the desert, but if you do, it is likely an ornamental plant that is being meticulously cared by someone.

Apparently, this plant has some pretty interesting antioxidant properties. The main way it is prepared is by powdering the root or stem bark, and using it as medicine. There's likely other ways to prepare it, but the main ways I found were through powdering bark.

In my reading, I learned a little more detail about antioxidants and why they're important. So basically, in living organisms, there is a balance between a cell degrading itself naturally and other components nourishing cells. Put plainly, in our bodies there is a pronounced balance between "life" giving processes and those that cause "death." But not as clear cut and black and white as it may seem, "life" and "death" are more on a spectrum of processes than defined one way or the other. What does this have to do with antioxidants?

Well, there's a lot of crap that your body can be exposed to, through diet, lifestyle, the air we breathe etc. Some of these things we're exposed to contain oxidizing agents that can have detrimental processes to cells in our body. Too much of a bad thing can really hurt you (but also too much of a good thing can also hurt you). Oxidizing means that it oxidizes parts of cells in your body, degrading them basically. An easy way to visualize oxidation is to think of iron oxide, which is rust, eating away at some old truck that has been rained on too many times. The truck is being oxidized, the same thing happening in your body, except a bit different than the truck rusting because we don't exactly "rust" in the same way the old truck would.

I'll spare you the complexities of all the different types of antioxidants and oxidizing agents but bottom line it there is a lot of each. Antioxidants work to clean up and tone the body's cells to keep processes efficient. So if we just keep consuming a ton of antioxidants, we're good right? Not exactly...

Science, and especially medical science is a work in progress. Interestingly, but not exactly surprisingly if you ask me, synthetic pharmaceuticals usually fare worse than a whole plant approach. Isolation and the synthesizing of chemicals and active compounds is a very heated debate, but the way things are looking, scientists are beginning to pay more attention to whole plants as opposed to just their active chemicals. Think of it like a human body. It's far more interesting to study how a hip joint is impacted and impacts the whole body versus separating that joint and studying it in isolation. If we just study that joint detached from the rest of the body, we never fully understand how a bad hip joint can be a precursor to all sorts of bone issues over time. If you just remove the hip joint and study that, you don't fully understand how it can impact the whole body, like load bearing, spinal complications over time, affecting someone's gait, etc. In another example, imagine if we good study living breathing gigantic dinosaurs instead of just extrapolating data and hypotheses from their fossils.

Well, same goes with plants. If you dice it up and select only a small potion, and study that, then it's harder to recognize what the whole plant is like and how the compounds in the plant interact with each other. So what, who cares you might be thinking? Let's go back to synthetic products for a bit. When you take a synthetic antioxidant, or a synthetic medicine for that matter, usually scientists have isolated active compounds for specific purposes. While the intentions are noble, and some synthetic products can be beneficial, usually these synthetic products do not perform as well as their whole plant or plant based counterparts. Don't tell the pharmaceutical companies that, although they already know and are actively engaged in misinforming the masses about things like a healthy diet and eating lots of plants. I mean, if modern medicine was primarily plant based, then even the poorest could afford it, and what money hungry pharmaceutical company wants that? Watching out for our best interests my ass...

Back to antioxidants. These things basically remove certain other things from the body to help improve cell processes. It's a complicated world, so it's kinda funny how people just hear something has antioxidants and automatically assume it's good for them, or at least that they can just consume that one item and they'll be "healthy" (the same thing happens with all these vitamin C products with people thinking you won't get sick if you just take them). Wrong! There's more than one kind of antioxidant, and they all can do different things to the body. Antioxidants are basically just removing things from the body that can react easily with important cell processes (i.e. oxidizing them), and therefore these oxidants can have detrimental effects. Things like too much reactive oxygen in the body, or too much iron/metals can promote chemical processes that aren't so great for healthy cells. Cell death occurs when basically the balance of anti-oxidation and oxidation isn't met anymore, specifically within the processes of cell mitochondria. This is why antioxidant consumption is still not going to prevent you from dying from old age, sorry.

But wait, there's more. When you're using synthetic compounds as medicine, such as synthetic antioxidants, then much of the time, the drug is much less complex than what would be found in the plant. That means that it can be too targeted, and this is a huge problem of modern medicine. It's why you have to take a pill to counteract the effects of another pill only to stay sick. Don't get me wrong, modern medicine is amazing with trauma and urgent care, but when it comes to daily life and preventative habits, it doesn't fare as well.

Back to white fringetree, the supposed plant star of this blog post. Well, this plant has some wonderful antioxidant properties, and as a medicine, it has hepatic (related to the liver, and liver processes) benefits. It has some pretty powerful antioxidant properties, and can remove a whole array of crap from the body to promote better liver function. However, one of the antioxidants it contains also has a strong metal chelating property. Huh? Chelating in simple terms means that it helps clean the body of metals, since chelating agents will bond to metals in the body and thus clean them out. However, too much a good thing can be detrimental. If you're consuming lots of white fringetree to help your liver, well, you're also consuming a pretty powerful metal chelating agent. This means that although it may be helping your liver in the short run, it might also be extracting too much iron and other important metals from your system. Too little iron in your system means you'll be anemic, too few metals also means that important cell processes cannot take place because your body won't have the proper materials for these important reactions. Moral of the story? Balance and diversity are key.

I'm going to refer back to the "it has antioxidants so that means it's healthy" statement meant earlier. I wish the message was more "produce and plants in general contain a vast diversity or antioxidants and good for you stuff, so diversity of diet is still one of the most important factors of health." Many people read "it's good for the liver" and automatically want to use only that. They'll binge drink and take a cup of herbal preparation of white fringetree root bark and say "all better," yet continue their fatty diets and shitty lifestyle. Sorry folks, that's not how plants, or a healthy life, work. Thinking that one plant, or even just a few plants will allow you to live a crappy lazy lifestyle and you'll "get away with it" is very misguided. It's how our modern medicine culture has raised us and lead us to believe that popping pills and quick medicine fixes are all we need to cure disease.

Sorry to say that although white fringetree has some good liver stimulating qualities, and outperforms synthetic antioxidants, it's not going to be a substitute for an active lifestyle, good social interactions, and a diverse and mainly plant based diet. So while this plant can be used to promote liver function, it's still not going to save you from liver cancer when you drink yourself to oblivion. Still, it has some pretty white flowers, and the root bark can likely be used in conjunction with an already healthy lifestyle that promotes liver function. The "rule" is simple. Eat lots of plants with lots of different colors, get out and about and be active in nature, drink plenty of clean water, have meaningful social interactions, and cut down on stress that does not grow you as a person (such as work stress, not working out stress). Don't forget how incredibly crucial sleep is. Then the white fringetree can stay as a pretty ornamental large shrub plant, and be used sparingly every so often.



References:

The Biota of North America Program
http://bonap.net/MapGallery/County/Chionanthus%20virginicus.png
http://www.bonap.org/MapKey.html

Bocsi, T. et al. "Plants’ native distributions do not reflect climatic tolerance." Diversity and Distributions, vol. 22, 2016, pp. 1-10. John Wiley & Sons Ltd, DOI: 10.1111/ddi.12432.

Global Biodiversity Information Facility
https://www.gbif.org

Gülçin, I. et al. "Antioxidant activity of lignans from fringe tree (Chionanthus viginicus L.)." Eur Food Res Technol, vol. 223, 2006, pp. 759-767. DOI 10.1007/s00217-006-0265-5.