Plastid terminal oxidase - a route to improving food security

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The most important challenge facing humanity in the 21st century ensuring that the growing world population can continue to be fed in a reliable way, against a backdrop of changes in climate induced by human activities, especially the burning of fossil fuels. Crops are especially vulnerable to fluctuations in weather conditions, with events such as droughts, heat waves and floods all liable to reduce yields. As such weather events are expected to increase in the future, we urgently need to breed plants with a greater capacity to tolerate these.The process of photosynthesis is at the forefront of plant interactions with their environment. Plants absorb light energy using molecules called chlorophylls, and use that energy to make sugars which feed the plant. Extreme weather does not stop light being absorbed, but it can stop it being used. When this occurs, the unused energy can instead cause damage to the leaf. In particular, it can give rise to the formation of highly reactive molecules, such as the bleach hydrogen peroxide. These can, if not controlled, destroy the leaf.The aim of this project is to investigate a new mechanism which protects plants from excess light. We have been working with a plant called salt cress (Eutrema salsugineum) which is a species found growing salt marshes. Salt cress is a relative of important crop plants such as cabbage and oil seed. We have identified a protein in this plant called the Plastid Terminal Oxidase (or PTOX for short) which we have shown can act as a safety valve for photosynthesis, dissipating excess light energy, when this cannot be used. PTOX has the potential therefore to improve stress tolerance in crop plants. When we take the gene for PTOX from salt cress and transfer it to another species, however, we are unable to detect any activity. We have recently shown that activity requires a change in the localisation of the PTOX protein in the leaf cells, moving it to a different compartment where it has not previously been seen.The aim of this project is to understand the processes involved in the relocalisation of PTOX in Eutrema and to attempt to transfer these to another species. We will use a combination of state of the art protein and gene expression analysis, combined with electron microscopy and genetic engineering to characterise the mechanisms involved in moving PTOX and to identify new genes which maybe required for this. At the end of the project we will have gathered new information to define the processes involved and will have tested certain genes to see if they play a role in the activation of PTOX.