| |
BOMI 120 Introduction to Cell Biology
Chris Wolverton, Ph.D.
Course Syllabus
Digital Laboratory Exercise – Auxin Transport
Pedagogical Aim
How to Search the Digital Resource Commons
Related Research
Auxin Transport During Gravitropism and Phototropism using a GFP-based Biosensor
A digital laboratory exercise made possible through a faculty-librarian collaboration using the Ohio Wesleyan Digital Resource Commons and the Mellon Foundation.
Plants are extremely sensitive to their environment, able to detect and respond to such stimuli as gravity, touch, light, moisture, and nutrient gradients. One of the most common outcomes upon sensing a stimulus is for the plant to undergo differential growth either toward or away from the stimulus. Growth responses toward or away from stimuli are known as tropisms. Plant tropisms have been the object of scientific study for over 200 years, with each successive generation of researcher applying current state-of-the-art technologies and approaches to further our understanding of the mechanisms responsible for growth regulation. Research on tropisms provides a point of integration today among the fields of cell biology, genetics, molecular biology, biophysics, biochemistry, and physiology.
The images in this project make use of a reporter gene known as GFP, which stands for green fluorescent protein, a naturally occurring protein found originally in the jellyfish, Aequoria victoria. The cloning of the gene encoding this fluorescent protein made it possible to label virtually any gene product in vivo, without the addition of toxic dyes, opening up a whole world of possible experiments in cell and molecular biology.
In the case of the images in the experiment published here, the GFP gene was fused to a promoter element that is activated in response to the plant hormone auxin (also known by its chemical name, indole-3 acetic acid). The specific details of this reporter gene were described in the article, "Gravity-regulated differential auxin transport from columella to lateral root cap cells."
Pedagogical Aim
Over the course of the past 20 years, cell biology has been revolutionized by the ability to visualize living cells and tissues labeled with fluorescent dyes and proteins through the use of confocal scanning laser microscopy. This powerful technique has opened a window into real-time cellular and sub-cellular dynamics and spawned entirely new areas of inquiry into the functioning of the cell. Unfortunately, this tool has remained firmly in the realm of the research lab due to its cost and complexity. The goal of this project is to introduce confocal microscopy as an analytical technique in an introductory-level cell biology class. The specific objectives include:
1. To expose students to a research image data set and the challenges associated with converting visual information into structured, quantitative observations.
2. To provide an example of reporter gene expression and to demonstrate the utility of reporter genes for understanding the regulation of gene expression in time and space.
3. To introduce the plant gravity sensing pathway as a useful model system for studying multicellular signal transduction.
Groups of students will be assigned one of the four treatment groups to analyze over the course of one week, after which time they will submit a score sheet for the group of images. Class discussion will compare the results of the four groups, highlighting the similarities and differences among the groups' approaches. Each group will then have a chance to revise their score sheets into a standardized format as decided collaboratively.
This digital collection consists of confocal laser scanning microscopy data sets using reporter genes to illustrate flux of plant hormones (auxin) in response to environmental cues. These data sets are fairly unique and illustrate important aspects of plant cell biology. The opportunity to make this data widely available is important for students who will be working with the data as well as important to the wider cell biology scholarly community.
Related Research
Mullen, J.L., Wolverton, C., Hangarter, R.P. (2005) Apical control, gravitropic signaling, and the growth of lateral roots in Arabidopsis (K.H. Hasenstein, H. Levine & D.M. Porterfield, eds): pp 1211-1217.
Ottenschlager, I., Wolff, P., Wolverton, C., Bhalerao, R.P., Sandberg, G., Ishikawa, H., Evans, M., Palme, K. (2003) Gravity-regulated differential auxin transport from columella to lateral root cap cells. Proceedings of the National Academy of Sciences of the United States of America, 100(5), 2987-2991.
Wolverton, C., Ishikawa, H., Evans, M.L. (2002a) The kinetics of root gravitropism: Dual motors and sensors. Journal of Plant Growth Regulation, 21(2), 102-112.
Wolverton, C., Mullen, J.L., Ishikawa, H., Evans, M.L. (2002b) Root gravitropism in response to a signal originating outside of the cap. Planta, 215(1), 153-157.
Mullen, J.L., Wolverton, C., Ishikawa, H., Hangarter, R.P., Evans, M.L. (2002) Spatial separation of light perception and growth response in maize root phototropism. Plant Cell and Environment, 25(9), 1191-1196.
Mullen, J.L., Wolverton, C., Ishikawa, H., Evans, M.L. (2000) Kinetics of constant gravitropic stimulus responses in Arabidopsis roots using a feedback system. Plant Physiology, 123(2), 665-670.
Wolverton, C., Mullen, J.L., Ishikawam, H., Evans, M.L. (2000) Two distinct regions of response drive differential growth in Vigna root electrotropism. Plant Cell and Environment, 23(11), 1275-1280.
Wolverton, C., Mullen, J.L., Aizawa, S., Yoshizaki, I., Kamigaichi, S., Mukai, C., Shimazu, T., Fukui, K., Evans, M.L., Ishikawa, H. (1999) Inhibition of root elongation in microgravity by an applied electric field. Journal of Plant Research, 112(4), 493-496.
Mullen, J.L., Turk, E., Johnson, K., Wolverton, C., Ishikawa, H., Simmons, C., Soll, D., Evans, M.L. (1998) Root-growth behavior of the arabidopsis mutant rgr1 - Roles of gravitropism and circumnutation in the waving/coiling phenomenon. Plant Physiology, 118(4), 1139-1145.
Wolverton, C., Evans, M., Ishikawa, H., Spalding, E. (1997) Suppression of Arabidopsis root gravitropism by the anion channel inhibitor, NPPB 5-nitro-2-(3-phenylpropylamino)-benzoic acid. Plant Physiology, 114(3), 1353-1353.
Young, L., Evans, M., Ishikawa, H., Wolverton, C., Soll, D. (1996) Kinetics of the gravitropic response of primary roots of the rgr1 mutant of Arabidopsis thaliana. Plant Physiology, 111(2), 599-599.
This exercise is a faculty-librarian collaborative digital pilot project in the sciences funded by the Mellon Foundation.
Chris Wolverton, Asst. Professor
Department of Botany / Microbiology
Deborah Carter Peoples,Science Librarian
Emily Haddaway, Digital Librarian
Ohio Wesleyan University Libraries and Information Services
|
