Plants make many 1000s of metabolites and these are accumulated throughout the plant. However, not all metabolites are accumulated everywhere nor are they all synthesised at the same time. For reasons of efficiency and affectivity, plants tend to accumulate different metabolites in different locations depending on their function in the plant. When metabolites are visible such as the red, blue and purple anthocyanins, we can readily see, for example, that these are often present in flowers and fruit of a certain species, but are not present in the leaves or roots. Similarly, the orange pigment lycopene, typical of ripe tomatoes, is generally not found at significant levels in any other part of the plant apart from the fruit. However, unfortunately, the vast majority of plant metabolites are not visible to the naked eye and so we have little idea how they are localised within organs and tissues.
We are making use of a new metabolomics imaging technology LAESI (Laser Ablated Electro-Spray Ionisation) to localise metabolites within plant tissues. We are using this approach to follow the response of plants to pathogen infection, pest attack and to determine where in tissues metabolites are accumulating following abiotic stress. The information gained can then be used to better understand the mechanisms of plant response to genetic and environmental perturbation.