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Abstract

Changes in redox status are a conspicuous feature of immune responses in a variety of eukaryotes, but the associated signalling mechanisms are not well understood. In plants, attempted microbial infection triggers the rapid synthesis of nitric oxide (NO) and a parallel accumulation of reactive oxygen intermediates (ROIs). In this context, I will discuss our work on S-nitrosylation, the addition of an NO moiety to a protein cysteine thiol to form an S-nitrosothiol, which is emerging as a key regulator of the plant defence response, controlling ROI synthesis, the accumulation of the immune activator, salicylic acid (SA) and hypersensitive cell death. Significantly, these findings have primed our studies of animal reference systems, which are providing key insights into biomedicine, as dysregulaltion of S-nitrosylation underpins a slew of human diseases. 
Another feature of plant immune function is the synthesis of a plethora of secondary metabolites that provide a chemical based defence system against a broad range of microbes and pests. Some of these natural products have emerged as important pharmaceuticals. Plant cell culture offers an attractive production platform for these chemicals but often is not a commercially viable strategy because of difficulties associated with culturing dedifferentiated plant cells (DDCs) on an industrial scale. To address this issue, in collaboration with industry, we have isolated, cultured and characterised innately undifferentiated cambial meristematic cells (CMCs). I will discuss how we are exploiting theses cells for the synthesis of high value pharmaceuticals during immune function.  
Selected References

• Yun, B.-W., Skelly, M.J., Yin, M., Yu, M., Spoel, S.H. and Loake, G.J. (2016). Nitric oxide and S-nitrosoglutathione function additively in plant immunity. New Phytologist (In Press).  
• Kneeshaw, S., Gelineau, S., Tada, Y., Loake G.J., and Spoel, S.H. (2014). Selective Protein Denitrosylase Activity of Thioredoxin-h5 Modulates Plant Immunity. Mol. Cell 56, 153–162. 
• Frungillo L., Skelly, M.J., Loake, G.J., Spoel, S.H. and Salgado, I. (2014). Nitric oxide generation and scavenging are coupled to nitrogen metabolism in plants. Nature Comm. 5, 5401. DOI: 10.1038/ncomms6401.  
• Yun, B-W., Feechan, A., Yin, M., Saidi, N. B.B., Yu, M., Le Bihan, T. Kang, J.-G., Kwon, E., Spoel, S., Pallas, J.A. and Loake, G.J. (2011). S-nitrosylation of NADPH oxidase regulates cell death in plant immunity. Nature 478, 264-268. 
• Lee, E.K., Jin, Joong, Y.-W., Park, H., Yoo, Y.M., Hong, S.M., Amir, R., Yan, Z., Kwon, E., Elfick, A., Tomlinson, S., Halbritter, F., Waibel, T., Yun, B.-W. and Loake, G.J. (2010). Plant cambial meristematic cells as a source for natural products. Nature Biotechnology 28, 1213-1217.