Abstract
The promoter of a chloroplastic β-carbonic anhydrase in the marine diatom Phaeodactylum tricornutum (PtCA1) is known to be under controls of CO2, light, and cAMP. We have already shown that three tandem repeat of a typical mammalian-cAMP-responsive element is critical for CO2 response of this promoter, Pptca1. This repeat sequence was designated as CO2/cAMP-responsive element, CCRE. In the present study, we searched and isolated 8 candidates of CREB/ATF superfamily cDNAs (PtbZIPs) from genome of P. tricornutum. These cDNAs were ligated into pET21a vector, and expressed in E. coli BL21(DE3). Of these gene products, proteins designated as PtbZIP2, 3, and 7 were found in soluble fractions. Gel shift assay using CCRE pentamer as a probe revealed that PtbZIP7 specifically bound to CCRE. RT-PCR assays showed that the expression level of PtbZIP7 was higher in air.
