Abstract
Expression of PtCA1, a pyrenoidal carbonic anhydrase (CA) in the marine diatom Phaeodactylum tricornutum, is regulated by ambient CO2 concentration at the transcriptional level. In our previous study, CO2/cAMP-response elements (CCRE1-3) were identified as CO2- and light-response cis-elements at the promoter region of ptca1 (Pptca1). It was also demonstrated that cAMP is a second messenger for this regulation. Our previous study also showed that the function of Pptca1 is ensured by the existence of CCRE2 with CCRE1 or 3. In this study, the function of promoter of the other pyrenoidal CA, ptca2, (Pptca2) was analyzed and compared to that of Pptca1. Repression of Pptca2 under high CO2 was not affected by the existence of light whereas that of Pptca1 required light for full repressive operation under high CO2. It was thus suggested that Pptca1 and Pptca2 have different mode of light-response. Structural analysis of Pptca2 revealed that the region required for CO2- and light-response includes CCRE sequences with distinct alignment compared to Pptca1.
