Chlorophyll α synthesis upon interruption and deletion of por coding for the light-dependent NADPH: protochlorophyllide oxidoreductase in a photosystem-I-less/chL- strain of Synechocystis sp. PCC 6803

Qingfang He, Daniel Brune, Ronald Nieman, Willem Vermaas

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The gene coding for the light-dependent NADPH:protochlorophyllide oxidoreductase (POR) was interrupted or deleted in a Synechocystis sp. PCC 6803 strain lacking photosystem I (PS I) as well as ChlL, which takes part in light-independent catalysis of protochlorophyllide reduction. Interruption of por by a kanamycin-resistance cartridge between the codons for M263 and V264 (about 83% into the coding region) did not abolish POR activity, but resulted in a decrease in the protochlorophyllide-(PChlide)-binding capacity of POR. Deletion of por in the PS I-less/ch/L- strain generated a mutant [PS I-less/ ch/L-/por (del)] which accumulated both monovinyl-PChlide and divinyl-PChlide and excreted PChlides into the medium. This mutant also synthesized small amounts of protochlorophyllide dihydrogeranylgeraniol ester (protochlorophyll) when it was grown under light-activated heterotrophic growth conditions. However, the mutant was still able to synthesize small amounts of normal chlorophyll a under weak continuous illumination, even though the quantum yield of chlorophyll a formation was reduced. Either protochlorophyll or PChlide reduction by an unspecific reductase or by a ChlB/ChlN complex could account For chlorophyll a synthesis in the PS I-less/chlL-/por (del) strain. Functional photosystem II (PS II) was assembled in this mutant, but the PS II/chlorophyll ratio was fourfold lower than in the PS I-less strain with normal chlorophyll synthesis. The PS I-less/chlL-lpor (del) mutant had a 77-K fluorescence emission maximum at 685 nm but no peak or shoulder at 695 nm when the cells were excited at 435 nm. Much of the chlorophyll in the PS I-less/chlL-lpor (del) mutant therefore seems to be associated with components other than PS II.

Original languageEnglish (US)
Pages (from-to)161-172
Number of pages12
JournalEuropean Journal of Biochemistry
Issue number1
Publication statusPublished - Apr 1 1998



  • Chlorophyll synthesis
  • Mutagenesis
  • Photosystem II
  • Protochlorophyll
  • Protochlorphyllide reductase

ASJC Scopus subject areas

  • Biochemistry

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