Arabidopsis Thaliana

Arabidopsis thaliana – Model Organism

This is my first ever University essay, so go easy on me alright?

A model organism can be described as “an organism that is widely adopted by the research community because of its ease of use for genetic analyses” (Szymanski, 2013). Arabidopsis thaliana is a weed with no agricultural impact, however it possesses a collection of characteristics that qualifies the plant as a model organism (Leonelli, 2007).  This essay will describe three characteristics making A. thaliana a suitable model organism, these characteristics being ease of transformation; short lifecycle; and small genome. It will outline how the impact of the A. thaliana research community, collaborative research approaches, and institutional influences all contributed to A. thaliana achieving model organism status.

In 1986 Kenneth Feldmann and David Marks discovered that A. thaliana could easily be transformed by incubating seeds with the bacterium Agrobacterium tumefaciens and a gene of interest (Feldmann & Marks, 1987). The result was a “collection of transgenic transfer DNA (T-DNA) insertion mutants” (Somerville & Koornneef, 2002). This finding led to other researchers cloning genes from the same collection, which was a significant milestone (Somerville & Koornneef, 2002). The techniques used to transform A. thaliana were improved over time and produced consistent high numbers of mutations in progeny (Somerville & Koornneef, 2002). The most modern method used to transform A. thaliana involves spraying A. thaliana flowers with the A. tumefaciens, a simple method producing many transformants (Somerville & Koornneef, 2002). Transformation is a process used to identify gene functions, and a valuable characteristic for any model organism (Somerville & Koornneef, 2002).

model idiot

The short lifecycle of A. thaliana is a characteristic that complements the ease in which the plant can be transformed. Under laboratory conditions, A. thaliana has a lifecycle of approximately 6-8 weeks, and 6 generations can be grown in a year (Koornneef & Scheres, 2001). In addition to the short life cycle, A. thaliana is self-fertilizing, and can produce thousands of progeny from one plant (Leonelli, 2007). A short life cycle is an advantageous characteristic as it allows researchers to quickly produce many progeny and isolate any genetic expressions or transformations.

A. thaliana has a small genome size for a flowering plant, which proved to be an important characteristic contributing to the plant achieving model organism status (Leonelli, 2007). A. thaliana has 5 chromosomes and an estimated 140 million base pairs, small in comparison to the wheat genome of approximately 17 billion (Szymanski, 2013). A smaller genome is beneficial for detailed molecular genetic analysis, and the A. thaliana Genome Initiative (AGI) was successful in sequencing the genome in 2000, making A. thaliana the first plant with a sequenced genome (Leonelli, 2007). Sequencing the genome assists with gaining knowledge of gene functions and applying the data gained to other plants or organisms. For example, a high percentage of human genes have orthologs conserved in A. thaliana, making the plant a useful tool for research in to human disease (Jones, et al., 2008). “70% of genes implicated in cancer have A. thaliana orthologs”, a percentage higher to that found in other model organisms such as Saccharomyces cerevisiae at 41%, and Drosophila melanogaster at 67% (Jones, et al., 2008). A small genome is a beneficial characteristic for any model organism, and with efforts currently underway to identify the estimated 25,000+ genes, it is likely that A. thaliana will continue to provide valuable data (Somerville & Koornneef, 2002).

Various social and institutional factors contributed to A. thaliana becoming a model organism. The A. thaliana community and early adopters were crucial to its success. In the 1930s, Friedrich Laibach noticed a wide variety of natural variation in the A. thaliana phenotype, and started collecting, classifying and sharing wild type mutants (Leonelli, 2007). Laibach would become the first in a community of individuals to recognise the potential of A. thaliana (Leonelli, 2007). A meeting on plant molecular biology in 1985 brought together key stakeholders that would eventually be involved in the revival of the A. thaliana community (Leonelli, 2007). David Meinke, Elliot Meyerowitz, Maarten Koornneef, and Shauna and Chris Somerville met at the meeting, becoming a group of close friends that shared common interests and an appreciation of A. thaliana’ potential (Leonelli, 2007). The strong bonds established between these people was a critical social factor contributing to awareness of A. thaliana as a model organism (Leonelli, 2007).

Building on strong social connections, the A. thaliana community implemented an interdisciplinary collaborative approach, sharing results amongst many different stakeholders in different locations (Koornneef & Meinke, 2010).  This collaborative approach or “community ethos” differed to traditional plant science, which involved little collaboration or centralisation of data, and a division of classical disciplines (Koornneef & Meinke, 2010). Laibach’s wild type mutants were left to Gerhard Röbbelen in Germany, who shared the collection with international colleagues in the United States (Leonelli, 2007). Röbbelen went on to start the annual A. thaliana Information Service (AIS) newsletter in 1965, providing updates on A. thaliana research, with the aim of improving communication and sharing knowledge (Leonelli, 2007). The organisation of research and research funding applications was well coordinated by the Multinational A. thaliana Steering Committee (MASC), who advocated the “share and survive” approach to research (Leonelli, 2007).  After the AGI successfully mapped the A. thaliana genome in 2000, the A. thaliana Information Resource (TAIR) setup an online database to house all A. thaliana data (Leonelli, 2007).  Shared resources and community ethos were critical factors contributing to A. thaliana becoming a successful model organism (Leonelli, 2007).

Various institutional factors contributed to A. thaliana becoming a very popular model organism (Leonelli, 2007). Termed the “publish or perish” mentality, new researchers were encouraged to study traditional model organisms such as the fruit fly, which was theoretically less interesting and competition between researchers was high (Leonelli, 2007). The potential of A. thaliana attracted geneticists and allowed them to research new ideas in a less competitive, highly collaborative and organised environment (Leonelli, 2007). As an indicator of the popularity of A. thaliana, the number of biologists conducting research on A. thaliana increased from 25 in the 1970s to approximately 16,000 in 2007, a significant increase (Leonelli, 2007). The A. thaliana community worked together to obtain research funding from organisations such as the NSF, NIH and European Commission, who were motivated by competition for prestige and recognised the potential of A. thaliana (Leonelli, 2007).  Institutional factors played a critical role in funding, and influencing the idea that it was acceptable for a plant to be used as a model organism for genetic analysis (Leonelli, 2007).

Various scientific, social and institutional factors played a role in A. thaliana becoming the model organism it is today. Characteristics such as short lifecycle, small genome, and ease of transformation highlighted A. thaliana’s potential. Supported by various institutions, a tight knit community of researchers utilised the plant’s characteristics to their advantage and rapidly established an organised, collaborative environment with shared resources. With continued research, the goal is that A. thaliana continues to provide valuable data and findings that can be applied to other plants and organisms.

 

References

Feldmann, K. A., & Marks, M. D. (1987). Agrobacterium-mediated transformation of germinating seeds of A. thaliana thaliana: A non-tissue culture approach. Molecular and General Genetics, MGG, 208(1), 1-9. doi:10.1007/BF00330414

Jones, A. M., Chory, J., Dangl, J. L., Estelle, M., Jacobsen, S. E., Meyerowitz, E. M., . . . Weigel, D. (2008). The Impact of A. thaliana on Human Health: Diversifying Our Portfolio. Cell, 133(6), 939-943. doi:10.1016/j.cell.2008.05.040

Koornneef, M., & Meinke, D. (2010). The development of A. thaliana as a model plant. Plant Journal, 61(6), 909-921. doi:10.1111/j.1365-313X.2009.04086.x

Koornneef, M., & Scheres, B. (2001). A. thaliana thaliana as an Experimental Organism. In eLS (pp. 1-6). doi:10.1038/npg.els.0002031

Leonelli, S. (2007). A. thaliana, the botanical Drosophila: from mouse cress to model organism. Endeavour, 31(1), 34-38. doi:10.1016/j.endeavour.2007.01.003

Somerville, C., & Koornneef, M. (2002). A fortunate choice: the history of A. thaliana as a model plant. Nature Reviews Genetics, 3(11), 883-889. doi:10.1038/nrg927

Szymanski, D. (2013). A. thaliana thaliana: The Premier Model Plant. In Brenner’s Encyclopedia of Genetics. Elsevier Inc. doi:10.1016/B978-0-12-374984-0.00088-7

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