The ultrastructure of a Chlamydomonas reinhardtii mutant strain lacking phytoene synthase resembles that of a colorless alga.
Chlamydomonas reinhardtii strains lacking phytoene synthase, the first enzyme of carotenoid biosynthesis, are white. They lack carotenoid pigments, have very low levels of chlorophyll, and can grow only heterotrophically in the dark. Our electron and fluorescence microscopic studies showed that such a mutant strain (lts1-204) had a proliferated plastid envelope membrane but no stacks of thylakoid membranes within the plastid. It accumulated cytoplasmic compartments that appeared to be autophagous vacuoles filled with membranous material. The lts1 mutants apparently lacked pyrenoid bodies, which normally house ribulose bisphosphate carboxylase-oxygenase (Rubisco), and accumulated many starch granules. Although these mutant strains cannot synthesize the carotenoid and carotenoid-derived pigments present in the phototactic organelle (eyespot), the mutant we examined made a vestigial eyespot that was disorganized and often mislocalized to the posterior end of the cell. The absence of a pyrenoid body, the accumulation of starch, and the disorganization of the eyespot may all result from the absence of thylakoids. The ultrastructure of lts1 mutant strains is similar to but distinct from that of previously described white and yellow mutant strains of C. reinhardtii and is similar to that of naturally colorless algae of the Polytoma group.
Inwood
William
W
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA.
Yoshihara
Corinne
C
Zalpuri
Reena
R
Kim
Kwang-Seo
KS
Kustu
Sydney
S
D000085:Acetates / Q000494:pharmacology; D020418:Algal Proteins / Q000378:metabolism; D019883:Alkyl and Aryl Transferases / Q000172:deficiency*; D001343:Autophagy / Q000187:drug effects; D015153:Blotting, Western; D002462:Cell Membrane / Q000648:ultrastructure; D002467:Cell Nucleus / Q000187:drug effects / Q000648:ultrastructure; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development / Q000648:ultrastructure*; D005407:Flagella / Q000187:drug effects / Q000648:ultrastructure; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D007425:Intracellular Membranes / Q000187:drug effects / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects / Q000648:ultrastructure; D010858:Pigmentation / Q000187:drug effects / Q000502:physiology*; D015203:Reproducibility of Results; D013213:Starch / Q000378:metabolism; D020524:Thylakoids / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D014617:Vacuoles / Q000187:drug effects / Q000648:ultrastructure
D000085:Acetates; D020418:Algal Proteins; D008565:Membrane Proteins; D013213:Starch; D019883:Alkyl and Aryl Transferases; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase