THE RED-, FAR RED- AND BLUE-LIGHT REGULATION OF THE PSBA RNA-BINDING PROTEIN GENES IN CHLAMYDOMONAS REINHARDTII SUGGESTS THE INVOLVEMENT OF A CRYPTOCHROME AND NOVEL PHYTOCHROME-LIKE PHOTORECEPTOR IN THE SIGNALING PATHWAYS
Pedro Anguiano, Amybeth Cohen, Laura Arce, Quinn Howard, Kathy Nguyen, Alex Powell.
California State University Fullerton, Fullerton, CA.
In the eukaryotic, unicellular, green alga Chlamydomonas reinhardtii, the photosynthetic D1 protein is translated from the chloroplast-encoded psbA mRNA. Translation of the mRNA is regulated by a set of nuclear-encoded RNA binding (RB) proteins (RB38, RB47, and RB60), which interact with a stem-loop structure in the 5’-untranslated region of the mRNA. Previous studies demonstrated that rb38, rb60, and psbO (encodes the photosystem II-associated oxygen evolving enhancer I protein) are induced by red light. To further characterize the light responses of these genes, dark grown C. reinhardtii cells were exposed to various combinations of light qualities and gene expression was measured by reverse transcription-polymerase chain reaction on the total extracted RNA. Preliminary data indicates that red and blue light induce the expression of the rb38, rb60, and psbO genes, and that far red light reverses the red light induction. These results suggest that a cryptochrome and yet to be identified phytochrome-like photoreceptor play a role in the signaling pathways of these genes. A bioinformatic analysis of the rb60 promoter has revealed the presence of a g-box and GATA motif, two red light-responsive cis-elements that may play a role in the red-light induction of the rb60 gene. To date, we have yet to identify prospective blue light cis-elements in the rb60 promoter. Future studies aim to further describe the light responses of the rb genes and identify putative red and blue light cis-elements in each of the rb gene promoters.