Hormone sensitivity of seasonal transcriptomes. (A,B) Venn diagrams of up-regulated transcriptomes (A) and down-regulated transcriptomes (B) related to season (HVC LD versus HVC SD), testosterone (HVC SD versus HVC SD + T), and area-specificity (HVC LD versus ENT LD) (Figure 4). (C-E) From the various resulting transcriptomes of these comparisons, we calculated the frequency of genes with an androgen response element (ARE) or estrogen response element (ERE) in their promoters. Numbers below the headers of (C-G) relate to the differential transcriptomes of (A) and (B). Many more genes are down-regulated (B) compared with up-regulated (A) in each of the comparisons: 833 genes are up-regulated seasonally in HVC, among which 208 are testosterone-inducible; 2,410 are down-regulated seasonally in HVC, among which 1,695 are testosterone-inducible. Genes containing ERE are enriched particularly among the testosterone-sensitive seasonal gene pool (C) compared with seasonal but not testosterone-sensitive genes (E) or random (not shown) gene pools. Among the down-regulated transcriptomes, AREs are particularly enriched among the testosterone-sensitive seasonal genes (D). The frequency of AREs and EREs in (D,E) is depicted as the percentage enrichment compared with ARE and ERE abundance in genes not expressed in HVC. (F-H) The frequency of canary-specific AREs (CAN-ARE) and of canary-specific EREs (CAN-ERE) among the various gene pools. Canary-specific means the AREs and EREs are absent in orthologous genes of the zebra finch genome. Percentage is based on all genes of a gene pool (here 208, 1,695 and 1,000; see Additional file 6 for gene lists). Note that AREs of testosterone-sensitive seasonally expressed genes (F,G) are conserved, that is, the frequency of CAN-AREs is much lower compared with genes not expressed in HVC (H). This is not the case for CAN-EREs.