ENVIRONMENTAL AND DEVELOPMENTAL REGULATION OF CAROTENOGENESIS IN THE DIMORPHIC FUNGUS MUCOR-ROUXII

Aerobic mycelium of wild-type Mucor rouxii accumulated about ten times higher amounts of the carotenoid pigment beta-carotene when grown con tinuously in the presence of light than the corresponding cultures gro wn in the dark. Carotenoid accumulation was dependent on light intensi ty, with the threshold located at about 10(-2) W.m(-2). Photocarotenog enesis in complex medium was more efficient with glucose as a carbon s ource. Carotenoid synthesis by M. rouxii mycelium was unaffected by bo th retinol acetate and retinal, which are stimulators of carotenogenes is in other zygomycetes. Carotenogenesis was significant in aerobic my celium but was almost undetectable in anaerobic mycelium as well as in aerobic or anaerobic yeast cells. This suggested an involvement of ox ygen in carotenoid synthesis by M. rouxii and the existence of develop mental regulation of the expression or operation of the pathway.