Defective myo-inositol-1-phosphate synthase production in an inositolless double mutant Neurospora crassa strain.

A slow growing inl+/- mutant was isolated from an inositol dependent (inl) Neurospora crassa strain. The latter strain produces defective myo-inositol-1-phosphate synthase which has residual activity. Inositol, similarly to that found in wild and inl mutant strains, represses the enzyme production in the inl+/- strain as well. Withdrawing inositol from the medium results in derepression of the enzyme synthesis. Derepression is hindered by cycloheximide. Inl+/- character in the double mutant is brought about by overproduction of the defective myo-inositol-1-phosphate synthase.