Mean expression level of core and non-core genes across the five most abundant taxa per sample. Per gene expression level is measured as a ratio - (Transcript abundance in RNA sample)/(Gene abundance in the DNA sample) - with abundance normalized to dataset size. 'Core' genes are determined individually for each taxon based on orthology with a closely related sister taxon, as described in the main text. Asterisks mark taxa for which expression ratios differed significantly between core and non-core genes (P < 0.001, t-test).
Stewart et al. Genome Biology 2011 12:R26 doi:10.1186/gb-2011-12-3-r26