Differences in expression patterns of photosynthetic genes in the dinoflagellate Alexandrium tamarense

In higher land plants, the expression pattern and mechanisms of transcriptional regulation of photosynthetic genes such as chl a/b-binding protein have been well studied. However, details of these mechanisms in dinoflagellates have not been reported. We isolated two cDNAs encoding light-harvesting complex proteins chl a/c-binding protein (CAC) and peridinin chl a-binding protein (PCP) from the dinoflagellate Alexandrium tamarense to investigate their gene expression patterns. Then we performed dot blot analysis to investigate the expression patterns of these two genes during a light/dark cycle. The mRNA levels of CAC were 7-fold higher during the light than during the dark period, while accumulated mRNA and protein levels of PCP were nearly constant during the cycle. In addition, we found that treatment with 3-(3, 4-dichlorophenyl)-1, 1-dimethyl urea (DCMU) decreased accumulated mRNA levels of CAC compared to the control cells, whereas PCP mRNA levels remained unchanged. This study confirmed that gene expression of PCP and CAC are differentially regulated although their function in photosynthesis is similar.