Plant metabolomics and its potential for systems biology research: background concepts, technology, and methodology

The "metabolome" comprises the entire complement of small molecules in a plant or any other organism. It represents the ultimate phenotype of cells, deduced from the perturbation of gene expression and the modulation of protein function, as well as environmental cues. Extensive advances over the past decade, regarding the high-throughput (HTP) nature of "omics" research, have given birth to the expectation that a type of "systems level" overview may soon be possible. Having such a global overview of the molecular organization of a plant in the context of a particular set of genetic or environmental conditions, be it at cell, organ, or whole plant level, would clearly be very powerful. Currently, we are far from achieving this goal; however, within our hands, plant metabolomics is an HTP and informative "omics" approach to both sample generation and data generation, as well as raw data preprocessing, statistical analysis, and biological interpretation. Within this chapter, we aim to describe the great attention given to experimental design to ensure that the correct sample set and control are included and to, thereby, enable reliable statistical analysis of the data. For as comprehensive metabolite coverage as possible, we advocate the use of multiparallel approaches; thus, we describe a step-by-step standardized method for Nuclear magnetic resonance spectroscopy, as well as discussing with reference to standardized methodologies the techniques of gas chromatography-time of flight/mass spectrometry, and liquid chromatography-mass spectrometry.