Beyond Peppers: Cross-Species Engineering
The Capsicum capsaicin pathway is not Capsicum-exclusive — the biochemistry is portable. Any plant host that can supply phenylalanine (for the vanillyl branch) and branched-chain amino acids (for the acyl branch) is a candidate. The question for each species is metabolic compatibility, delivery method, and regeneration protocol.
Tomato: High Feasibility
Solanum lycopersicum is closely related to Capsicum (both Solanaceae) and has an active phenylpropanoid pathway in fruit tissue. The main gap is Branch 2 (the acyl chain) — tomato lacks pAMT and BCAT activity in fruit. Adding these two genes plus AT3 to tomato is a minimal three-gene construct and the most studied cross-species capsaicin transfer target.
Rice: Moderate Feasibility
Oryza sativa has limited phenylpropanoid flux in grain tissue — Branch 1 must be boosted in addition to adding Branch 2 and AT3. FBA modeling predicts lower yield in rice than in tomato, but the economic value of a heat-carrying rice grain (novel product category, high demand) makes it worth pursuing. The platform includes validated delivery protocols for japonica varieties.
Basil: Emerging Target
Ocimum basilicum has unusually high terpenoid and phenylpropanoid flux, making it an attractive host. The cooling pathway (menthol → TRPM8) and the heat pathway (capsaicin → TRPV1) can in principle be installed side by side — creating a 'cool heat' combination construct. FBA modeling for basil is included in multi-axis M2 constructs on the platform.