Bitter Taste Attenuation
Bitterness is detected by ~25 TAS2R (bitter taste receptor) GPCRs expressed on Type II taste cells in fungiform and circumvallate papillae. Each receptor responds to a different chemical class — glucosinolates in brassicas, caffeine in coffee, quinine in tonic water, naringenin in grapefruit. Eliminating bitterness in a crop requires identifying the specific TAS2R ligand and disrupting its biosynthesis.
Glucosinolates in Brassicas
Cruciferous vegetables (broccoli, kale, Brussels sprouts) contain glucosinolates — sulfur-containing glycosides — that hydrolyze to isothiocyanates during chewing. Isothiocyanates potently activate TAS2R38, the principal bitter receptor for this class. The TAS2R38 ligand elimination constructs in the Scoville Splice catalog target the glucosinolate biosynthesis genes MYB28, MYB29, and CYP79F1 in Brassica species.
Engineering Strategy
Because glucosinolates also have health-associated bioactivities (cancer-preventive isothiocyanates), complete elimination is not always desirable. The IFI-B axis scores attenuation relative to baseline — allowing partial suppression tuned to consumer preference. CRISPR knockdown of transcription factors (MYB28/29) rather than biosynthesis genes allows dosable attenuation without full pathway elimination.