Light regulation has been investigated in the zygomycetes Phycomyces blakesleeanus, Mucor circinelloides and Pilobolus crystallinus.
The two genes for the enzymes phytoene desaturase (carB) and the bifunctional phytoene synthase/carotene cyclase (carRA in Phycomyces, carRP in Mucor) are responsible for synthesis of beta-carotene.