A suppressor mutation in the alpha-phycocyanin gene in the light/glucose-sensitive phenotype of the psbK-disruptant of the cyanobacterium Synechocystis sp. PCC 6803.
psbK encodes a small transmembrane component of PSII. Here we report that the psbK-disruptant of Synechocystis sp. PCC 6803 cannot survive under photomixotrophic conditions of light and glucose after transient growth, while the wild type is able to grow. A spontaneous yellow-green mutant that recovered the sustained growth under the same conditions was isolated from the psbK-disruptant. Instead of recovery, the mutant largely lost photoautotrophic growth. By phenotype complementation, the mutation was identified in cpcA as a sequence replacement with a close downstream segment, generating an inverted repeat of 23 bp. The mutant phenotype was characterized by (i) the complete loss of alpha- and beta-phycocyanin; (ii) increased accumulation of PSII; and (iii) greatly reduced transcripts harboring cpcA in abundance and in size. The inverted repeat generated in cpcA probably led to the early termination of transcription. A possible mechanism for such a mutation is discussed.
Kobayashi
Mari
M
Department of Life Sciences (Biology), The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902 Japan.
Okada
Katsuhiko
K
Ikeuchi
Masahiko
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D016153:Genes, Suppressor; D005947:Glucose / Q000494:pharmacology*; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010798:Phycocyanin / Q000235:genetics*; D046939:Synechocystis / Q000235:genetics*
D001426:Bacterial Proteins; D010798:Phycocyanin; C061381:psbK protein, cyanobacteria; D005947:Glucose