Towards understanding the functional difference between the two PsbO isoforms in Arabidopsis thaliana--insights from phenotypic analyses of psbo knockout mutants

Photosynth Res. Oct-Dec 2008;98(1-3):405-14. doi: 10.1007/s11120-008-9325-y. Epub 2008 Aug 16.


The extrinsic PsbO subunit of the water-oxidizing photosystem II (PSII) complex is represented by two isoforms in Arabidopsis thaliana, namely PsbO1 and PsbO2. Recent analyses of psbo1 and psbo2 knockout mutants have brought insights into their roles in photosynthesis and light stress. Here we analyzed the two psbo mutants in terms of PsbOs expression pattern, organization of PSII complexes and GTPase activity. Both PsbOs are present in wild-type plants, and their expression is mutually controlled in the mutants. Almost all PSII complexes are in the monomeric form not only in the psbo1 but also in the psbo2 mutant grown under high-light conditions. This results either from an enhanced susceptibility of PSII to photoinactivation or from malfunction of the repair cycle. Notably, the psbo1 mutant displays such problems even under growth-light conditions. These results together with the finding that PsbO2 has a threefold higher GTPase activity than PsbO1 have significance for the turnover of the PSII D1 subunit in Arabidopsis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism*
  • Gene Expression Regulation, Plant
  • Guanosine Triphosphate / metabolism*
  • Light
  • Molecular Sequence Data
  • Mutation
  • Phenotype
  • Photosystem II Protein Complex / genetics
  • Photosystem II Protein Complex / metabolism*
  • Protein Isoforms / metabolism
  • RNA, Plant / metabolism
  • Stress, Physiological*


  • Photosystem II Protein Complex
  • Protein Isoforms
  • RNA, Plant
  • photosystem II manganese-stabilizing protein
  • Guanosine Triphosphate