The great petunia carnage of 2017: A clicker case study using petunias to describe effect of genetic modification on the biochemistry of flower color and phenotype in plants

Authors: BOURY, NANCY - Iowa State University; VAN DEN BOGAARD, MAARTJE - University Of Texas - El Paso; WLEZIEN, ELIZABETH - Iowa State University; PETERS, NICK - Iowa State University; Wise, Roger

Submitted to: CourseSource
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2024
Publication Date: 6/27/2024
Citation: Boury, N., Van den Bogaard, M., Wlezien, E.B., Peters, N., Wise, R.P. 2024. The great petunia carnage of 2017: A clicker case study using petunias to describe effect of genetic modification on the biochemistry of flower color and phenotype in plants. CourseSource. https://doi.org/10.24918/cs.2024.15.
DOI: https://doi.org/10.24918/cs.2024.15

Interpretive Summary: Case studies used in case-based learning are authentic and represent an issue in the field that is studied. Case-based learning (CBL) is an active, and structured approach to learning and is often used to clarify and expand content that students have worked on prior to the introduction of the case. In our case we chose the Great Petunia Carnage incident of 2017. This is a case of genetic modification (GM) of a popular flower (petunias) that naturally only occurs in pink and purple hues. A plant scientist discovered orange petunias, which were the result of a genetic modifications. The changes to these plants had not been approved for commercial breeding and sale, which led to a worldwide effort to identify and destroy the illegal plants. In this case study we explore how the genetics of the petunia plants were altered, how these changes were detected, and the ultimate results of the discovery of these unregulated petunias. Case studies are an accessible teaching method for new faculty, as the structure structures and guides the lesson so even instructors with little experience can adopt case studies successfully and achieve great results with their students. CBL is scalable to larger class sizes when coupled with personal response systems, also known as ‘interrupted case studies’ or ‘progressive disclosure’ where information is fed to students bit by bit and who must piece together these bits of information to solve the case. Impact: Case-based learning allows for instructors to use authentic problems from their field in the classrooms, and as such, increase relevance of the content that is covered in the course. In general, students in courses using case studies report increased confidence and belief that they are learning and retaining important concepts.

Technical Abstract: In this case study, students examine the difference between genotype and phenotype by studying the mechanisms by which commercially available petunias have been bred to have different phenotypes (flower colors). Students review the central dogma of biology, connecting the phenotype of the petunia plants to their genotype and the existence of a transgene in plants with unusual (orange) flowers. The case study describes the molecular and biochemical mechanisms by which the secondary metabolites that determine flower color are produced. This case is designed as a “clicker case” utilizing personal response systems or “clickers” to engage students in a large classroom setting. This approach allows for students to collaborate actively, while the instructor is leading and pacing the lecture in a way that allows to engage with large groups. As students work through the case, they work out the processes needed to add transgenes to a plant, as well as how we can detect these modifications decades later. Lastly, instructors can lead a discussion of the scientific and social issues surrounding the creation, use, and regulation of genetically modified organisms.