Metabolomics is the science of small molecules. Metabolomics analyses are performed using an advanced set of analytical platforms designed first to separate and then to detect many 100s of metabolites that are present in an extract of a plant tissue. The technologies being developed for these large-scale, potentially unbiased analyses are greatly changing our way of thinking about what is possible in plant biology. We are applying both Liquid Chromatography and Gas Chromatography together with Mass Spectrometry to study the biochemical composition of contrasting plant materials. Metabolomics is already giving plant scientists deeper insights into the complexity of plant metabolism and plant metabolic composition than were ever possible before.
Broad potential applicability already ranges from understanding the considerable complexity of primary metabolic networks in Arabidopsis, to the changes which occur in the biochemical composition of leaves which have been subjected to drought stress or insect attack. Results are revealing valuable information on how plant metabolism, while strictly controlled, is also highly dynamic. Plants, being sessile organisms, have to respond very rapidly to changes in their immediate environment and some of the earliest changes are centred upon a shift in their metabolic composition. Furthermore, with the parallel rapid development in complementary technologies such as Next Generation DNA Sequencing and sequencing-based transcriptomics approaches, we are now in a strong position to effectively use metabolomics as a generic approach to support crop-based research and breeding. Our research covers a wide range of species from tomato and rice to arabidopsis and melon.
Metabolomics for rice improvement
We are using metabolomics to define what we mean by high quality in rice. Rice is by far the world’s most important food crop. Furthermore, the majority of the 2 billion extra people expected to arrive on this planet in the next 40 will also be rice eaters. We drastically need improved rice varieties which combine the features of high yield with high quality. To achieve this we first need to understand what the biochemical basis is of rice aroma and taste- the two key quality traits. We are using GCMS approaches to analyse the aroma profiles of a population of rice genotypes and combining this with human sensory analysis we aim to identify the most dominant odour compounds driving rice aroma and taste. Similarly, the presence of so-called ‘off flavours’ which are negative quality attributes, can also be found and identified. Whether such off flavours are already present in the unpolished grain or whether the appear during processing prior to sale can also be evaluated. By combining detailed metabolomics approaches with advanced population genetics we shall identify the Qualitative Trait Loci (QTLs) – and eventually the genes - which are associated with the biosynthesis of these volatile compounds. This information shall then be exploited in strategic, targeted breeding programmes aimed to combine quality traits with other desirable traits in the rice crop.
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.