Effect of Bitter Compounds on the Expression of Bitter Taste Receptor T2R7 Downstream Signaling Effectors in cT2R7/pDisplay-G α 16/gust44/pcDNA3.1 (+) Cells

Abstract

Bitterness is an important taste sensation for chickens, which provides useful sensory information for acquisition and selection of diet, and warns them against ingestion of potentially harmful and noxious substances in nature. Bitter taste receptors (T2Rs) mediate the recognition of bitter compounds belonging to a family of proteins known as G-protein coupled receptors. The aim of this study was to identify and evaluate the expression of T2R7 in chicken tongue tissue and construct cT2R7-1 and cT2R7-2-expressing HEK-293T cells to access the expression of PLCβ2 and ITPR3 after exposure with different concentrations of the bitter compounds. Using real-time PCR, we show that the relative expression level of T2R7 mRNA in 5, 1, 0.1, and 10^-3 mM of camphor and erythromycin solutions and 5 mM of chlorpheniramine maleate solutions was significantly higher than that in 50 mM KCL solutions. We confirmed that the bitter taste receptor T2R7 and downstream signaling effectors are sensitive to different concentrations of bitter compounds. Moreover, T2R7-1 (corresponding to the unique haplotype of the Tibetan chicken) had higher sensitivity to bitter compounds compared with that of T2R7-2 (corresponding to the unique haplotype of the Jiuyuan black-chicken). These results provide great significance of taste response on dietary intake to improve chicken feeding efficiency in poultry production and have certain reference value for future taste research in other bird species.

Figure 1

Relative expression levels of T2R7 mRNA in tongue tissue of chicken stimulated by different concentrations of (a) camphor, (b) chlorpheniramine maleate, (c) erythromycin, (d) benzoin, (e) chloramphenicol, (f) quinine, and (g) parthenolide, as determined by real-time PCR. The relative gene expression was measured by qPCR and normalized to GAPDH, and a 50 mM KCL solution was the negative control. Each bar represents the mean ± SE of the results from 2 to 3 independent experiments performed in triplicate. Different small letters on the bar indicate significant differences at P < 0.05.

Figure 2

Relative expression levels of PLCβ2 mRNA in cT2R7-1/pDisplay-Gα16/gust44/pcDNA3.1 (+) and cT2R7-2/pDisplay-Gα16/gust44/pcDNA3.1 (+) cells stimulated by different concentrations of (a) camphor, (b) chlorpheniramine maleate, (c) erythromycin, (d) benzoin, (e) chloramphenicol, (f) quinine, and (g) parthenolide, as determined by real-time PCR. The relative gene expression was measured by qPCR and normalized to GAPDH, and the vector-control was the negative control. Each bar represents the mean ± SE of the results from 2 to 3 independent experiments performed in triplicate. Different small letters on the bar indicate significant differences at P < 0.05.

Figure 3

Relative expression levels of ITPR3 mRNA in cT2R7-1/pDisplay-Gα16/gust44/pcDNA3.1 (+) and cT2R7-2/pDisplay-Gα16/gust44/pcDNA3.1 (+) cells stimulated by different concentrations of (a) camphor, (b) chlorpheniramine maleate, (c) erythromycin, (d) benzoin, (e) chloramphenicol, (f) quinine, and (g) parthenolide, as determined by real-time PCR. The relative gene expression was measured by qPCR and normalized to GAPDH, and the vector-control was the negative control. Each bar represents the mean ± SE of the results from 2 to 3 independent experiments performed in triplicate. Different small letters on the bar indicate significant differences at P < 0.05.