Separate (+) and (-) mating type cultures of Blakeslea trispora synthesized: (a) labeled trisporic acid B and trisporic acid C when incubated with labeled, partially purified extracts isolated from opposite mating type cultures; (b) unlabeled trisporic acids when incubated with labeled glucose and unlabeled extracts isolated from opposite mating type cultures; and (c) over 100-fold less trisporic acids when incubated with labeled extracts isolated from the same mating type cultures. Thus, separate (+) and (-) cultures synthesize mating type-specific precursors of trisporic acids.

Separate plus and minus cultures of Blakeslea trispora synthesize small amounts of trisporic acids under specific conditions. These amounts are expressed as a percentage of the trisporic acids (50 mg/liter of medium) synthesized by mixed plus-minus cultures in 5 days. Plus cultures, without additives from minus cultures, synthesize 0.1% trisporic acids. Plus cultures synthesize 0.4% trisporic acids when stimulated by M-factor, a mating-type-specific component synthesized by minus cultures. Minus cultures, without additives from plus cultures, do not synthesize even 0.0001% trisporic acids. Minus cultures synthesize 1% trisporic acids when stimulated by P-factor, a mating-type-specific component synthesized by plus cultures. Minus cultures synthesize M-factor when stimulated by π, a component synthesized by plus cultures. We speculate that (i) minus cultures synthesize a component, μ, which stimulates P-factor synthesis in plus cultures, and (ii) both M-factor and P-factor are precursors of trisporic acids.