Fig. 8

The Metabolome as a Bridge in the Genotype to Phenotype Map. Phenotypic variation, represented by the bottom plane, is influenced by the action of a large number of genes and genetic variants (upper plane) on a smaller number of metabolites or metabolic pathways. Direct influences on phenotype are shown as dark lines whereas indirect connections are shown with grey lines. Genetic variation can influence the levels of individual metabolites or the relationship between metabolites and, as a result, affect metabolic pathways that share direct connections to phenotype; or, genetic variation can affect phenotype more directly (not depicted). Two or more genes might act epistatically to influence the level of a single metabolite, and a single gene might act pleiotropically on multiple metabolites