Abstract
As cyanobacteria contain multiple psbA and psbD genes for D1 and D2 proteins of photosystem II, these genes could be disrupted and replaced without loss of photoautotrophic growth. We constructed recombinant strains from a mesophilic Synechococcus elongatus PCC 7942 that carry psbAI and psbDI genes encoding thermostable D1 and D2 proteins from Thermosynechococcus vulcanus. When solubilized thylakoid membrane proteins were analyzed by Western blotting using an antibody against the thermostable D1-1 protein, the T. vulcanus D1-1 was scarcely assembled into PSII complex from a recombinant S. elongatus GRPS201 carrying only replaced psbAI gene. In contrast, the replaced psbAI gene was transcribed abundantly in the GRPS201 strain, suggesting a low efficiency for translation or assembly of D1-1 protein. We now construct a recombinant cyanobacterium from GRPS201 in which psbDI gene ORF was replaced by that from T. vulcanus to test the assembly of thermostable D1-D2 heterodimer in the mesophilic strain.
