Complete separation of the β,ε‐ and β,β‐carotenoid biosynthetic pathways by a unique mutation of the lycopene cyclase in the green alga, Scenedesmus obliquus

Abstract

The mutant, C-2A′-34, lacks the β, ϵ-carotenoids, α-carotene, lutein and loroxanthin. When grown under heterotrophic or mixotropic conditions this strain develops significantly higher levels of β-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 β,ϵ-carotenoids and modification of the pool of β,β-carotenoids neither prevent the proximal pigment-protein complexes of photosystems I and II from developing nor cause any short term photosensitivity. The increase in the β,β-carotenoids in C-2A′-34 apparently compensates for the loss of the β,ε-carotenoids required in formation of the proximal and distal antennae systems but not in the LHCs