Two functional psbD genes in the cyanobacterium Synechococcus sp. strain PCC 7942.

摘要: The cyanobacterium Synechococcus sp. strain PCC 7942 has two copies of the psbD gene which encodes D2 polypeptide photosystem II (PSII) reaction center. One genes, psbDI, overlaps open reading frame another gene, psbC; psbDII is monocistronic. Gene inactivation experiments had previously shown that dispensable under normal laboratory growth conditions. However, similar with psbDI never produced viable psbDI-inactivated mutants, presumably because psbC expression depends on transcription through psbDI. described here were designed to assess need for independent psbC. A strain, AMC027, was engineered in a second copy expressed from locus. Northern (RNA) blot analysis confirmed both and gave rise dicistronic messages containing sequences AMC027. In this genetic background, it possible inactivate creating AMC050 indicating functional. Western immunoblot showed products psbC, PSII proteins CP43, respectively, present thylakoids AMC050, but at reduced levels relative wild type, mutant psbDII-inactivated mutants. consistently formed small colonies plates competed poorly mixed-culture experiments. This suggested that, although not essential viability, locus required produce sufficient CP43 optimal growth. Images