We measured gene expression tissue specificity using a dataset of publicly available Sanger sequences for H. annuus developed by the Compositae Genome Project . Briefly, these libraries were constructed using eleven different tissues from two genotypes (callus, roots, disk and ray flowers, pre-fertilized flowers, developing kernel, chemically treated seedlings, environmentally stressed roots, environmentally stressed shoots, germinating seeds, environmentally stressed flowers, and hulls, see for details). These libraries were Sanger sequenced to generate a total of 44,000 barcoded reads. We demultiplexed and compared all reads (blastx, e-value < 1e-10) against our reference transcriptome of 16,312 genes. We defined expression specificity (range 0–11) as the total number of libraries (11) minus the number of libraries where a gene scored at least one hit as in .