Field of Science

Rare Mosses and Liverworts of England

It has been a full week with little time for me to work up my own blog post. Instead I encourage you to check out a post over on the IAB blog by a bryological colleague, Juan Carlos Villarreal. It is a book review of a new text focusing on rare mosses and liverworts of England. He gives you the highlights of the book and includes the details of one rare moss species Telaranea murphyae Paton. Enjoy!

Two Structures, One Set of Genes

When presented with a problem it is typically easier to solve it with tools at your disposal rather than inventing something new. This is also the case for plants and animals. When presented with a developmental or evolutionary challenge, it is often easier for them to use genes that already exist in their genetic toolkit to respond to the challenge.

Rhizoids are thin filaments of cells that anchor leafy moss plants onto their growth surface, which can be soil, rock, or trees, just to name a few. Rhizoids also function in water uptake. They help by creating many capillary spaces in which water can be move from the soil to the plant. However, rhizoids are not the only structures that are able to take up water in mosses. The leafy gametophyte plants can absorb water through many parts of their body including leaves and stems. 

The water uptake structures that you are probably more familiar with are roots. They are underground organs that function in water uptake and anchor the sporophytes of vascular plants into the soil. Near the tips of each root there are elongated, filamentous cells (root hairs) that increase the surface area through which the roots can take in water. 

Though root hairs and rhizoids have similar functions and they both start with the letter 'R', these two structures have completely independent evolutionary origins. By that I mean that root hairs are not rhizoids that have been changed and modified over evolutionary time. Another piece of evidence that points to them being evolutionary independent is that rhizoids are only present on the gametophytes, whereas root hairs are only on the sporophytes. Having structures that are exclusive to opposite generations typically indicates that have evolved independently. 

So, root hairs and rhizoids have similar functions, structurally they are both filamentous in shape, but what about the genes that control their development. Might they be using the same or similar parts of their genetic toolkit to build these two structures? 

Scientists examined this by figuring out the genes that are important for forming the root hairs in flowering plants, then looking to see if these same genes are also important for root hairs in mosses (Menand et al 2007; Pires et al 2013). The figure below shows some of their results. Let me walk you through it. On the left are mosses will brown rhizoids growing from the base. On the right are flowering plant roots with thin root hairs sticking out of the sides. WT and Col0 are what the plants look like naturally with no changes to the genes. 

Part of Figure 4 from Menand et al 2007

They found a group of related genes in mosses and flowering plants that influence both rhizoid and root hair formation. Pprsl1, Pprsl2, and rhd6-3 are the names of three members of this group of genes. 

What we see on the left is that they knockout/turn off Pprsl1 = rhizoids still formthey knockout/turn off Pprsl2 rhizoids still formbut when they turn both of them off  = no to only a few rhizoids form. 

On the left, center panel they turn off the gene rhd6-3 and the root does not make any root hairs. The coolest part of the study is that they are able to knock out the gene that makes root hairs, then use the moss gene to control the formation of root hairs. They are using a moss gene to control the production of root hairs in a flowering plant. Pretty wild!

This is just a small part of the story where they show that root hairs and rhizoids are controlled by the same network of genes. I think that it is a great example of plants using the genetic tools at their disposal to build similar structures on completely different parts of the plant in distantly related species. 

Check out the publications for more details about their experiments and findings. 

ResearchBlogging.orgMenand B, Yi K, Jouannic S, Hoffmann L, Ryan E, Linstead P, Schaefer DG, &; Dolan L (2007). An ancient mechanism controls the development of cells with a rooting function in land plants. Science (New York, N.Y.), 316 (5830), 1477-80 PMID: 17556585

Pires ND, Yi K, Breuninger H, Catarino B, Menand B, &; Dolan L (2013). Recruitment and remodeling of an ancient gene regulatory network during land plant evolution. Proceedings of the National Academy of Sciences of the United States of America, 110 (23), 9571-6 PMID: 23690618

Do you have Pteridomania?

On the title page of her book Fern Fever: The Story of Pteridomania Sarah Whittingham informs us of the following definitions.
"Pteris Greek word for a fern, derived from pteron, meaning feather or wing. Pteridophytes The ferns and fern allies. Pteridologist One who studies ferns scientifically. Pteridomania Fern madness. Pteridomaniac One who suffers fern madness."
I just started exploring this book written about the Victorian obsession with ferns. It is a large coffee-table sized book with a myriad of color images and photos of all things fern. The introduction covers how the fern craze began in the 1850's with collectors traveling the world and sending ferns back to England for cultivation. With the invention of the Wardian case, a small terrarium, ferns were brought into people's homes. At the same time many authors were publishing books about growing ferns and the types of ferns native to Britain. Naturalist and gardeners alike could not get enough of them. Ferns even made it into fashion as a design embellishment on dresses. 

I think that it is going to be a fun and educational read. I would recommend it for anyone who is already obsessed with ferns or would like to join in the craze. It will also be appealing to the history-minded and lovers of the Victorian era.   

At this time, science was the realm of mostly learned, wealthy white men. Women with botanical interests, also white and wealthy, collected, drew, and dried plant specimens under the purview of a gentle hobby. They knew little about how ferns reproduced. One fantastical idea was that they flowered only once per year and the spores could only be collected at night. Around the same time Wilhelm Hofmeister was just publishing his findings on the alternation of generations and plant life cycles. Interesting to think how far science has come both in our knowledge about plants and increased inclusiveness of people from diverse backgrounds. 

I leave you with a poem that Sarah Whittingham includes in her book on page 40. I especially like it because it contains a shout-out to my favorite ferny friends, the mosses.  

Auld Botany Been was wont to jog
Thro' rotten slough and quagmire bog 
O'er brimful dykes and marshes dank, 
Where Jack o' Lanterns play and prank,   
To seek a cryptogameous store 
Of mosses and carex and fungus hoare, 
Of ferns and brakes and such-like sights
 As tempt out scientific weights
On winter's day; but most his joy
Was finding what's called Osman's Roy.
- Plues A Summer Study of Ferns  

September 2013 Desktop Calendar

This image from one of our hikes in South Tahoe last month. We started at the end of a tiny windy road that ran along Fallen Leaf Lake and hiked up to Gilmore Lake. These Polytrichum mosses were growing along the edge of the lake. They make for a very busy image. So busy that it is a little challenging to see the calendar. Hopefully your September is not nearly as busy as this photo!

1 - Single click on the image to open it up in a new window. (If you use the image directly from the blog post you will lose a lot of resolution.)

2 - Right-click (or ctrl-click) on the image, and chose the option that says, "Set as Desktop Background" or "Use as Desktop Picture". The wording may vary.

3 - If the image does not fit your desktop neatly, you may have to adjust the image (Mac: System Preferences - Desktop and Screen Saver - Desktop; Windows: Control Panel - Display - Desktop) and choose "Fill screen" as the display mode of your background image.