| This project going to be… | Experimental (lab/field based) |
| Email | gail.preston@biology.ox.ac.uk |
| Position held | Professor / Director |
| Title of Project | Understanding how metal and reactive oxygen species protect metal hyperaccumulating plants against plant disease |
| Institution Department and Address | Department of Biology |
| Oxford, Oxfordshire OX1 3RB |
| United Kingdom |
| Full Name of Supervisor | Gail Preston |
| Date of Project Commencement | 26/06/2023 |
| Duration (weeks) | 10 |
| Brief Description of Project | Metal hyperaccumulation is defined as the uptake and storage of exceptionally high concentrations of a metal in the aerial tissues of a plant. Our work using the model metal hyperaccumulating plant Noccaea caerulescens, which is capable of accumulating zinc, nickel and cadmium, has provided strong support for the hypothesis that metal accumulation provides a direct defence against plant pathogens through the toxicity of accumulated metal to microorganisms, a hypothesis sometimes referred to as the “elemental defence” hypothesis. However, the amount of metal accumulated by N. caerulescens depends on metal concentrations in the local environment, which means that metal alone may be insufficient to provide protection in the context of varying environmental metal concentrations. An unanswered question is the extent to which metal acts in conjunction with other defensive mechanisms to inhibit pathogen growth, providing protection against disease even in circumstances where accumulated metal may be insufficient to directly limit infection. One factor that restricts pathogen growth in non-metal hyperaccumulating plants is the production of reactive oxygen species (ROS). We have shown that N. caerulescens exhibits an oxidative burst in response to pathogen elicitors and that plants that are exposed to increasing levels of zinc show increasing superoxide production. We have also recently shown that the presence of sub-lethal concentrations of zinc reduces ROS tolerance in the model plant pathogen Pseudomonas syringae. In this project we aim to further examine how metal hyperaccumulation interacts with ROS to limit infection by addressing the following questions: 1) Does ROS act synergistically with nickel to inhibit bacterial growth? We will examine whether nickel and hydrogen peroxide act synergistically to limit growth of the model bacterial pathogen Pseudomonas syringae, using bacterial growth assays and roGFP as a reporter of bacterial redox status. 2) Does metal accumulation lead to increased oxidative stress in P. syringae during infection? We will grow N. caerulescens hydroponically with varying levels of zinc or nickel and infect plants with P. syringae expressing roGFP to examine bacterial redox status, in conjunction with assays for bacterial multiplication, gene expression and viability. We will also monitor changes in apoplastic and chloroplastic ROS to assess how bacterial oxidative stress corresponds with ROS levels in planta. 3) Does oxidative stress in pathogens correlate with the distribution of metal in plant tissues? In collaborative work with Konstantin Ignatyev at Diamond Light Source we are using synchrotron X-ray fluorescence to study the distribution of metals in healthy and infected N. caerulescens leaves. The student will be able to assist with these experiments to study how metal distribution correlatives with bacterial oxidative stress, gaining experience of advanced spectroscopy and imaging techniques. |
| Attach the recommended reading for the project | Fones H.N., Preston G.M. (2013). Trade-offs between metal hyperaccumulation and induced disease resistance in metal hyperaccumulator plants. Plant Pathology 62, 63-71. |
| Fones, H., Davis, C.A.R., Rico, A., Fang, F., Smith, J.A.C. and Preston, G.M. (2010) Metal hyperaccumulation armors plants against disease. PLoS Pathogens 6, e1001093 |
| Fones H., Eyles C.J., Bennett M.H., Smith J.A.C., Preston G.M. (2013) Uncoupling of ROS accumulation and defence signalling in the metal hyperaccumulator plant Noccaea caerulescens. New Phytologist 199, 916-24 |
| Fones H.N., Preston G.M., Smith J.A.C. (2019) Variation in defence strategies in the metal hyperaccumulator plant Noccaea caerulescens is indicative of synergies and trade-offs between forms of defence. Royal Society Open Science 6, 172418 |
| Fones, H. and Preston, G.M. (2012) Reactive oxygen and oxidative stress tolerance in plant pathogenic Pseudomonas. FEMS Letters 327, 1-8 |
| Kopittke, P.M., Punshon, T., Paterson, D.J., Tappero, R.V., Wang, P., Blamey, F.P.C., van der Ent, A., Lombi, E. (2018). Synchrotron-based X-Ray Fluorescence Microscopy as a technique for imaging of elements in plants. Plant Physiology 178, 507–523 |
