COMPLETE SEPARATION OF THE BETA,EPSILON-CAROTENOID AND BETA,BETA-CAROTENOID BIOSYNTHETIC PATHWAYS BY A UNIQUE MUTATION OF THE LYCOPENE CYCLASE IN THE GREEN-ALGA, SCENEDESMUS-OBLIQUUS

The mutant, C-2A'-34, lacks the beta, epsilon-carotenoids, Lu-carotene, lutein and loroxanthin, When grown under heterotrophic or mixotropic conditions this strain develops significantly higher levels of beta-carotene and violaxanthin than does the original developmental mutant of Scenedesmus, C-2A', The decrease in chlorophyll a and chlorophyll b observed in C-2A'-34 is accompanied by the near absence of the LHC. The light intensity dependence of greening of this strain is comparable to that of C-2A'; the loss of the beta,epsilon-carotenoids and modification of the pool of beta,beta-carotenoids neither prevent the proximal pigment-protein complexes of photosystems I and TI from developing nor cause any short term photosensitivity. The increase in the beta,beta-carotenoids in C-2A'-34 apparently compensates for the loss of the beta,epsilon-carotenoids required in formation of the proximal and distal antennae systems but not in the LHCs.