GENETICS AND REGULATION OF CAROTENE BIOSYNTHESIS

Colour mutants are conspicuous and convenient genetic markers, but there have been few studies on the genetics of carotene biosynthesis. Recent work with the fungus Phycomyces has identified two main structural genes: carB, responsible for phytoene dehydrogenase, and carR, responsible for lycopene cyclase. Four copies of the first enzyme and two of the second constitute an enzyme complex carrying out all reactions from phytoene to 3-carotene. The pathway is regulated by a variety of environmental agents with the participation of several genes. Thus, cars mutants overaccumulate 3-carotene and carA mutants lack practically all carotenes. Surprisingly, carAcarR are segments of a single, bifunctional gene. The investigations carried out with Neurospora and other microorganisms are briefly reviewed from the viewpoint of the results with Phycomyces. © 1979, Walter de Gruyter. All rights reserved.