| In the unicellular green alga Chlamydomonas reinhardtii , nuclear-encoded proteins (RB38, RB47, and RB60) bind to the 5 '-untranslated region of the psbA mRNA to activate translation. In order to investigate the expression characteristics of the nuclear-encoded genes that represent these psbA binding proteins, the wild type and the Y-1 (yellow) strains of C. reinhardtii were utilized. The RB38 and RB60 mRNAs accumulated primarily in response to light, while the RB47 mRNA accumulated in a constitutive manner. RB38 and RB47 protein accumulation was greater in light-grown cells than in dark-grown cells, while RB60 protein accumulation was constitutive. The RB protein complex isolated from wild type and Y-1 light-grown cells had greater affinity for the 5'-UTR of the psbA mRNA than the complex isolated from dark-grown cells. These results clearly point to light as one of the controlling determinants in the expression of the RB genes and their interaction with the psbA mRNA. |
