Abstract
In the marine diatom Phaeodactylum tricornutum, intracellular cAMP concentration is thought to increase under High CO2 condition, and this signal represses transcription of carbonic anhydrase gene, ptca1. In this study, degrading enzyme of cAMP, cAMP-phosphodiesterase (cAMP-PDE), were characterized in P. tricornutum. cAMP-PDE activity in diatom lysate was measured by a method, which utilizes adenylate kinase reaction and lactate fermentation pathway. As a result, cAMP-PDE activity was detected in both soluble and insoluble fractions of diatom lysates. Candidate genes of cAMP-PDE were searched from diatom database, and 10 membrane-bound and 2 soluble type genes were found. Eight membrane-bound type genes were cloned and, semiquantitative RT-PCR was carried out on mRNAs obtained from cells grown in air and High CO2.All 8 genes had primary structures, which possess activity domains of both adenylyl cyclase and cAMP-PDE in the single open reading frame.
