Expression of zfT1R and zfT2R genes in gustatory tissues. Tissues containing taste buds were sectioned, and hybridized with digoxigenin-labeled riboprobes for each of the zfT1Rs and zfT2Rs as indicated on the left. The transcripts of zfT1R1, zfT1R2a, zfT1R2b, zfT1R3, zfT2R1a, and zfT2R1b were detected in the taste buds of the lips, gill rakers, and pharynx. The frequencies of zfT1R- and zfT2R-positive cells were lower than that of zfPLC-β2-positive cells. No signals for zfT1Rs or zfT2Rs were detected in the olfactory epithelium, while signals for zf5.24, an ortholog of goldfish olfactory receptor 5.24 gene, were detected in the adjacent section. The black label in olfactory epithelium hybridized with probe for zfT2R1a is a cluster of endogenous pigments. Scale bars at the bottom of each column=10 μm.

Co-expression of zfTRs with zfPLC-β2. Sections of pharyngeal region were hybridized with zfTR and zfPLC-β2 probes. The signals of probes were represented as pseudocolors (green for zfTRs and red for zfPLC-β2). The cells positive to zfT1R3 (A) or zfT2R1a (D) were included in the cells positive to zfPLC-β2 (B and E) as indicated by the yellow signals in merged images (C and F). Scale bar=10 μm.

Relationships in expression among zfTRs. Sections of pharyngeal region were hybridized with three kinds of probes in the combinations indicated by colored letters at the bottom of the panels: zfTRs and zfPLC-β2 (A–K) and three zfTRs (L). The signals of probes were represented as pseudocolors (green, red and blue). A relative population of cells expressing each receptor gene to zfPLC-β2-expressing cells is represented by bar under the panels, and percentage of co-expression between zfTRs is illustrated with colors. The blue bar under the panel A represents 10% population of zfPLC-β2-positive cells. Scale bar=10 μm. (M) Venn diagram illustrating the relationships in zfTR expression.