Compartmental, Selective and Reversible Redox Signalling in Plant Immunity

Supervisors: Dr Steven H. Spoel, Dr David J. Clarke

Project Description:

Plants are continuously exposed to many different disease causing agents, including pathogenic bacteria, fungi, viruses, and herbivorous insects. Each plant cell is thought to be capable of defending itself by launching immune responses that are specific to the intruder encountered. Cellular oxidation-reduction (redox) reactions are intimately associated with the successful mounting of immune responses in all multicellular organisms. Redox reactions are underpinned by the production of different reactive oxygen- and nitrogen-containing molecules that drive the cell’s content and environment into a more oxidized state. Nitric oxide (NO) and hydrogen peroxide (H2O2) play especially important roles in plant immunity as they are capable of post-translationally modifying proteins, which can alter protein function, cellular localization, conformation, and activity.

Despite the importance of redox homeostasis to developmental and stress responses, it has not yet been fully exploited as a trait in crop improvement strategies. This is predominantly due to the belief that perturbation of redox signalling leads to many undesired pleiotropic effects. Our findings, however, demonstrate that redox signalling is separable into specific branches that are controlled by members of the evolutionary conserved Thioredoxin (TRX) family [ref. 1, 2]. Plant genomes encode for dozens of TRX enzymes, suggesting numerous different redox signalling branches could exist. Thus, understanding how TRX enzymes control distinct redox signalling branches will allow their exploitation as redox-based traits for crop improvement [ref. 3].

In this PhD project you will engage in innovative genomic and proteomic strategies to dissect specific redox signalling branches regulated by different TRX enzymes. Moreover, you will investigate the selective substrate repertoires of TRX enzymes and assess how oxidation/reduction affects substrate activity. This will generate an in depth understanding of how signalling by reversibly oxidised proteins is controlled and employed by the plant cell to establish effective immune responses.

1. Kneeshaw S, Gelineau S, Tada Y, Loake GJ, Spoel SH (2014) Selective protein denitrosylase activity of Thioredoxin-h5 modulates plant immunity. MOLECULAR CELL 56: 153-162.

2. Kneeshaw S, Keyania R, Delorme-Hinoux V, Imrie L, Loake GJ, Le Bihan T, Reichheld J-P, Spoel SH (2017) Nucleoredoxin Guards against Oxidative Stress by Protecting Antioxidant Enzymes. PROC. NATL. ACAD. SCI. USA (PNAS) 114: 8414-8419.

3. Mata-Pérez C, Spoel SH (2018) Thioredoxin-mediated redox signalling in plant immunity. PLANT SCIENCE in press (doi: 10.1016/j.plantsci.2018.05.001).

If you wish to apply for this project, please go to this link.