Abstract
It is known that the promoter of chloroplastic β- carbonic anhydrase in the marine diatom Phaeodactylum tricornutum (PtCA1) under the control of CO2 via the second messenger cAMP. It is also known that a bZIP type transcription factor binds to CO2 responsive cis element in the promoter resion of ptca1 (Pptca1).However, the upstream signal system is not known. In this research, transcription factors which may target the CO2 / cAMP response elements (CCRE) in Pptca1 was searched and localized. Diatom homologues of human ATF6 family sequence (PtbZIP1~8) was cloned and expressed in E. coli. PtbZIP7 which is already known to be one of binding factors of CCREs was labeled by GFP and localized in the nucleus of P. tricornutum cells. A tool to determine the subcellular location of cAMP occurrence was also developed in the present study. The human exchange proteins directly activated by cAMP (Epac1) gene was fused in between the cfp and the yfp or the venus and expressed either in E. coli or P. tricornutum cells. FRET efficiency of this fusion protein was related to cAMP concentrations.
