Complete separation of the beta,epsilon- 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, alpha-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 II 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.
Bishop
N I
NI
Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331, USA.
Urbig
T
T
Senger
H
H
D002338:Carotenoids / Q000096:biosynthesis*; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000460:Chlorophyta / Q000201:enzymology* / Q000235:genetics; D019753:Intramolecular Lyases; D007535:Isomerases / Q000235:genetics*; D008027:Light; D045342:Light-Harvesting Protein Complexes; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll; D002338:Carotenoids; C037184:chlorophyll b; D007535:Isomerases; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase; D000077194:Chlorophyll A