Abstract
Nitrogen is an essential nutrient for plant cells. We are using a unicellular red alga, Cyanidioschyzon merolae, as the model system to analyze the nitrogen regulation in photosynthetic eukaryotes. In this study, we examined in detail the physiological changes of C. merolae in case of nitrogen depletion. In addition, we identified and characterized a transcription factor that is responsible for expression of nitrogen assimilation genes in C. merolae. DNA microarray and Northern blot analyses revealed that transcript of the gene encoding CmMYB1, an R2R3-type MYB transcription factor, increased 1 hour after nitrogen depletion. The CmMYB1 protein started to accumulate after 2 hours and reached a peak after 4 hours after the nitrogen depletion, correlating with the expression of key nitrogen assimilation genes. The nitrogen depletion-induced gene expression disappeared in a CmMYB1 null mutant. Chromatin immunoprecipitation analysis and electrophoretic mobility shift assays using crude cell extract demonstrated that CmMYB1 specifically occupied these nitrogen-responsive promoter regions only under nitrogen-depleted conditions.
Ref) Imamura et al. (2009) PNAS 106, 12548-1255
