April 2, 2013

As I write this, I have dirt underneath my fingernails and I love it.  Spring is here, and I have begun playing in the dirt and cheering for my budding vegetable garden seedlings.  I love the food plants provide us, but they’re also fascinating models for understanding cell biology and developmental biology.  Today’s image is from a paper identifying a player in the development of stomata, which are important plant organs.

Stomata are pore organs on leaves that regulate gas and water vapor exchange in plants.  They are made of pairs of guard cells that regulate the size of the stomata openings to let air in and oxygen out.  A recent paper describes the identification of a protein that regulates the maturing and functioning of stomatal guard cells.  Negi and colleagues identified SCAP1, a transcription factor, that when mutated results in irregularly-shaped guard cells.  These mutants also lack the ability to control stomatal opening and closing.  SCAP1 regulates the transcription of known guard cell development genes.  The images above show a wild-type plant (top) with normal developing stomata at all stages (mature stomata is right-most image).  In a scap1 mutant (bottom), however, later stages of stomata development are defective and result in stomata with a floppy or irregular appearance.

Negi, J., Moriwaki, K., Konishi, M., Yokoyama, R., Nakano, T., Kusumi, K., Hashimoto-Sugimoto, M., Schroeder, J., Nishitani, K., Yanagisawa, S., & Iba, K. (2013). A Dof Transcription Factor, SCAP1, Is Essential for the Development of Functional Stomata in Arabidopsis Current Biology, 23 (6), 479-484 DOI: 10.1016/j.cub.2013.02.001
Copyright ©2013 Elsevier Ltd. All rights reserved.

April 23, 2012

I love plants. I support our local botanical garden, I’ve been a vegetarian for almost 17 years, and I talk to (and hug) our yard’s new trees to welcome them to the family. Clearly I’m pro-plants. So why aren’t there more plant cell biology pictures on my blog? I have no excuses. Today, enjoy this lovely image from Arabidopsis, the go-to model plant in cell biology.

Rapid growth in a developing organism can provide challenges for the tissue, especially in tissues where the cells adhere to each other as they do in plants. In a developing plant, this rapid growth combined with differences in cell growth throughout the tissue causes mechanical strain and stress on the cells. A recent paper describes how katanin, a microtubule severing protein, is key in allowing the cells to respond to mechanical stress in the plant Arabidopsis. In this paper, Uyttewaal and colleagues imaged cell growth the in the plant’s stem cell niche, the shoot apical meristem, and found heterogeneity in the cell growth rates. Katanin mutants, however, had decreased growth variability in this same tissue. In normal plants, cortical microtubule arrays arrange themselves toward the regions of high mechanical stress, and this in turn affects growth. Uyttewaal and colleagues found that this directional arrangement of microtubule arrays is affected in katanin mutants, as seen in the images above. Images show shoot apical meristem tissue with microtubule arrays fluorescently tagged in green and their orientation marked in red. Microtubule arrays in wild type tissue (left) have a circumferential orientation in the peripheral zone (bottom, zoomed), while microtubule arrays in katanin mutants lacked a similar pattern (right images).

Uyttewaal, M., Burian, A., Alim, K., Landrein, B., Borowska-Wykręt, D., Dedieu, A., Peaucelle, A., Ludynia, M., Traas, J., Boudaoud, A., Kwiatkowska, D., & Hamant, O. (2012). Mechanical Stress Acts via Katanin to Amplify Differences in Growth Rate between Adjacent Cells in Arabidopsis Cell, 149 (2), 439-451 DOI: 10.1016/j.cell.2012.02.048
Copyright ©2012 Elsevier Ltd. All rights reserved.

October 6, 2011

Plants are underrepresented on this blog. Thankfully, this isn’t a food blog with only carnivorous cholesterol-thickened readers. But still, plants need representing (woot woot!) and today’s lovely images should help.

Plant cell communication is accomplished through the direct cell-to-cell transport of transcription factors, which are proteins that regulate gene expression. Just as in animal cells, plant development depends on these signals being relayed correctly. A recent paper describes how one transcription factor called SHR (SHORT-ROOT) is trafficked. Koizumi and colleagues identified a SHR-interacting protein called SIEL, which also associates with endosomes. Without SIEL, plant embryos arrest in early development. The images above are cross-sections of roots. Top root is normal, with one layer each of 8 endodermis (E) and 8 cortex (C) cells. SIEL mutants (middle, bottom) had multiple endodermis and cortex layers, each with more cells than in wild-type. The double arrows indicate the thickness of these tissue layers combined.

Koizumi, K., Wu, S., MacRae-Crerar, A., & Gallagher, K. (2011). An Essential Protein that Interacts with Endosomes and Promotes Movement of the SHORT-ROOT Transcription Factor Current Biology, 21 (18), 1559-1564 DOI: 10.1016/j.cub.2011.08.013
Copyright ©2011 Elsevier Ltd. All rights reserved.

July 19, 2010

The development of individual organs involves precise patterning of cells. The regulation of cell growth and division plays a large role in generating this patterning, and a recent paper used the sepal of the plant Arabidopsis thaliana as a model to investigate this. The sepal is the outer green, leaf-like floral organ on the plant, and is made of a distinct pattern of cells with a wide range of sizes. Image above is a scanning electron micrograph of an Arabidopsis sepal with giant cells colored red.

Reference: Adrienne H. K. Roeder, Vijay Chickarmane, Alexandre Cunha, Boguslaw Obara, B. S. Manjunath, Elliot M. Meyerowitz. Authors’ PLoS Biology paper can be found here.