a, Confocal microscopy images of circumvallate papilla taste buds from a TRPM5–BFP (labelling sweet and bitter TRCs32, pseudo-coloured red); T2R32–GFP (labelling bitter TRCs) double-labelled transgenic mouse. These are the animals used in the profiling of sweet/umami and bitter TRCs. Note the expected co-expression of bitter taste receptors and a subset of TRPM5+ cells (right; TRPM5+, but T2R− TRCs are indicated by asterisks). b, Taste bud from a TRPM5–BFP transgenic mouse showing co-expression of the BFP reporter (pseudo-coloured red) and PLCβ2 (a marker of sweet, umami and bitter TRCs32, green). c, Taste bud from a PKD2L1–TdTomato transgenic animal demonstrating expression of the TdTomato reporter (red) in sour TRCs (marked by CAR4 (ref. 34), green). d, qRT–PCR illustrating the relative expression of several candidate connectivity molecules in bitter, sweet and sour TRCs. Data are presented as mean + s.e.m. relative to the expression levels in the whole circumvallate papilla (referred to as taste tissue); n = 3.