Once again, I think that the authors conclusions are supported by the data. We see that both fluorescent probes label the same location within the taste buds, and therefore must be coexpressed in the labeled cells. Taste bud cells express multiple T2R receptors. This figure very clearly supports this claim. In Figure 7, doubly-labeled FISH was used to visualize the expression of T2Rs with gastducin and T1Rs.
Dotted lines represent the area of sectioned taste buds.
This data support the claim that T2Rs are gastducin-linked receptors. If I were to stop here, I would still be very skeptical about the function of T2Rs. However, Chandrashekar et al. To test whether all T2Rs function in the same taste modality, one could use homologous recombination to create knock-out mice for selective subsets of mT2R receptors. I would suspect that this would definitely reduce the number of compounds producing a bitter taste response, but would not expect that other modalities would be effected because I would hypothesize that all T2R receptors function in the same bitter modality.