Abstract
C. merolae is a photoautotrophic unicellular red algae living in acid hot springs, and has the simplest cell architecture among eukaryotes. In addition to the minimally redundant gene content, many nuclear and chloroplast genes are regulated by light conditions. These features provide a good model for studying light signal transduction in plant cells.
In higher plants, DET1 is known as a negative regulator of light-dependent transcription, and widely influences cellular functions as photomorphogenesis. DET1 binds nuclear chromatin and associates with CUL4-DDB1. While these lines of evidence suggest that DET1 might affect transcriptional regulation via chromatin modification, the underlying mechanism remains unclear.
In this study, we constructed a null mutant strain lacking the DET1 homolog gene in C. merolae. This mutant showed growth inhibition under light-dark cycles. As observed in higher plants, several light-regulated nuclear and chloroplast genes were highly expressed even under dark. Currently, we are analyzing the relationship between DET1 and histone H3 lysine 9 di-methylation as a representative chromatin mark for transcriptional silencing.
