| Translation of the chloroplast-encoded psbA mRNA is regulated in the unicellular green alga Chlamydomonas reinhardtii by a complex of four nuclear-encoded binding proteins (RB38, RB47, RB55, and RB60), which bind to the 5'-untranslated region of the RNA. The rb38 and rb60 genes, as well as the nuclear-encoded oee1 gene, are expressed in response to red light. A red light photoreceptor, homologous to the phytochrome-like proteins Cph1 and Cph2 from the cyanobacterium Synechocystis sp. strain PCC6803, was identified using tblastn searches of the Chlamydomonas reinhardtii genome database. A red/far-red light shift did not alter the accumulation of the rb38, rb60, or oee1 mRNAs, indicating that the red light photoreceptor may not be photoreversible. Further elucidation of the signal transduction pathway showed that the calmodulin gene is induced by red light, and that the induction of the rb60, rb38, and oee1 genes is regulated by the Calmodulin protein. Future studies will better elucidate the signal transduction pathway that regulates the expression of rb60, rb38, and oee1 genes in Chlamydomonas reinhardtii. |
