Practicalities

1. The introductory lectures will need to be prepared based on what is taught at your institution.
2. For the lab sessions, it is easier if you organise the students by the research question they have chosen. We generally encourage our students to work in groups of 4.
3. The number of pots of plants is suboptimal to encourage students to prioritise the most important/informative stress treatments. This could be increased depending on available resources. Seed stocks are best if bulked every 1-3 years.
4. In GUS staining, X-GlcA is cleaved by GUS enzyme at the ß1 glucuronic bond between glucuronic acid and 5-bromo-4-chloro-3-indolyl. Oxidation and dimerisation of the latter then results in the precipitation of water-insoluble blue dichloro-dibromo-indigo precipitate. This is reasonably well contained within the cells where GUS enzymes is present.
5. If students spray too much salicylic acid (SA) or aspirin on the plants, a hyposensitive response may occur, resulting in cell death. This can be explained by the ‘French flag’ model, where no to low levels of SA mean NPR1 is bound by NPR4 and non-active. At intermediate levels, NPR4 is released from NPR1 leading to SA-mediated disease resistance. At high levels, NPR1 is bound by NPR3 and leads to cell death.
6. Plants treated with salt may show stress phenotypes such as anthocyanin accumulation. Plectosphaerella-infected plants should have necrotic spots where the inoculum was applied.
   There might be mild symptoms of SA and aspirin treatment in the form of chlorosis.
7. We take photos of the best plant phenotypes and GUS staining results to use in the final discussion and Q&A session.
8. Our assessment linked to this practical is a 1,200 word report in a scientific format (Introduction, Materials and Methods, Results, Discussion). This is marked by graduate teaching assistants. We have previously tested understanding of the practical through multiple choice questions as part of an end of semester exam covering both lecture and practical content.

References/Further Reading

Pieterse CMJ, Leon-Reyes A, Van Der Ent S, Van Wees SCM, 2009. Networking by small-molecule hormones in plant immunity. Nature Chemical Biology 5, 308-16.

Ton J, Mauch-Mani B, 2004. Beta-amino-butyric acid-induced resistance against necrotrophic pathogens is based on ABA-dependent priming for callose. Plant J 38, 119-30.

Ton J, Flors V, Mauch-Mani B, 2009. The multifaceted role of ABA in disease resistance. Trends Plant Sci 14, 310-7.