This image of an Arabidopsis leaf shows the cells in green and airspaces in yellow. It has been digitally reconstructed from x-ray CT data gathered at the Hounsfield Facility, University of Nottingham.
As a plant scientist with an interest in growth and development I have been lucky enough to work with a wide range of plant models - from moss to rice to hibiscus... but I have to confess to a long-standing soft-spot for Arabidopsis thaliana. Often described as the 'lab rat' of plant science, this unassuming plant (some would say boring-looking, but I think it's kind of cute!) is known to many gardeners as a common weed. Some of the traits that make it a successful garden nuisance also make it a great model - it's easy to grow, it has a short lifecycle, and it tends to set very large numbers of tiny seeds. Moreover, as the first plant to have its genome fully sequenced back in the year 2000, the knowledge of this plant's genetics that we have accumulated over the last 20 years provides a fantastic resource for scientists, unparalleled in any other plant model.
Generating genetically modified Arabidopsis plants in which gene expression can be manipulated in various ways is very simple. All we have to do is dip the flower buds into a solution of plant-modifying 'agrobacteria' containing the DNA that we want to introduce to the plant. These bacteria can insert their DNA, including any that we have added, into the forming seeds, so the next generation of seedlings should express the DNA that we introduced. Furthermore, Arabidopsis seed lines in which various genes are not expressed ('knocked-out') are readily available to order, so it is not always necessary to make modifications from scratch by the floral dip method.
During my PhD in the Fleming group at the University of Sheffield I studied genes involved in regulating how leaves develop, focussing in particular on the proportion of airspace inside the leaf, and the impact of the amount of airspace on photosynthesis and water use. For this project it was really useful to be able to order Arabidopsis seed lines in which particular genes are knocked out. I used high resolution x-ray scanning technology at the Hounsfield Facility, University of Nottingham, to image and quantify the cells and airspaces inside the leaves of these mutant plants to determine whether loss of each of my candidate genes did indeed modify leaf development.
My current research project in the Sparkes group at the University of Bristol aims to understand how sub-compartments within cells (collectively termed 'organelles') interact with one another. These interactions are important for the exchange of signals and of intermediate compounds in metabolic pathways, but in plant systems we know very little about how they regulation of organelle contact. It is possible to visualise organelle movement in live cells by genetically introducing fluorescent labels fused to proteins at the surface of organelles. Fluorescent proteins are available in a wide range of colours, so by tagging different organelles with different fluorescent colours I can easily distinguish them under the microscope - this also makes for beautiful, multicoloured images! I introduce the fluorescent-tagged proteins into my Arabidopsis plants using the floral dip method described above.
There are some disadvantages to focussing too heavily on Arabidopsis as a plant model. For a start, one of the most fascinating things about plants is their tremendous diversity, which can never be understood by working on just one species. Furthermore, Arabidopsis is not a crop plant, so mutants with increased productivity are not useful in themselves. However, the rapid pace of scientific advancement that we can achieve by working with this well-understood model provides crucial insights that can underpin improvements in commercially useful species.
Further reading
For a summary of Arabidopsis research please click here to read more!
Alice is a Research scientist in plant cell biology in the Sparkes Laboratory, University of Bristol. You can find Alice on twitter @AliceBaillie1
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