Generation and characterization of His-tagged-PsbA-expressing transformants of Chlamydomonas reinhardtii that are capable of photoautotrophic growth

Histidine tags attached to subunits of photosystem II (PSII) have proven to be very useful tools for isolation and purification of the complex for investigation of its components. However, it has been reported that Chlamydomonas reinhardtii transformants carrying N-terminal histidine-tagged version of the PSII D1 reaction center protein could not grow photoautotrophically. We report here a successful generation of C. reinhardtii transformants expressing histidine-tagged version of the PsbA protein that are capable of photoautotrophic growth. Biochemical and physiological analyses revealed that the histidine tag present at the N terminus of the D1 subunit did not cause total instability to the PSII complex as assessed by their phototrophic growth and oxygen evolution capability. Simple one-step affinity column chromatography also revealed that the histidine-tagged D1 subunit as well as its associated proteins could be effectively purified. These transformants could potentially serve as very good tools for the study of the PSII complex particularly the D1 protein.