Accumulation of a complex form of β-carotene byPhycomyces blakesleeanus cytoplasmic mutants.

Phycomyces blakesleeanus colour mutants of a new class have been isolated. The mutants form red mycelia when grown in the dark and show vegetative segregation. The affected gene, amedcarE, behaves as an extranuclear genetic factor. The red phenotype ofcarE mutants is caused by the accumulation of β-carotene in a form showing spectral shift to longer wavelengths. The spectral shift is abolished in vitro by heat or protease treatment and in vivo by the presence of light or retinol.