Arabidopsis cDNA clones isolated by transcomplementation of the fission yeast cAMP phosphodiesterase mutant.

Abstract

We isolated three kinds of Arabidopsis thaliana cDNA clones that could rescue the mating-defective phenotype of the pde1 mutant of fission yeast Schizosaccharomyces pombe, which lacked cAMP phosphodiesterase. One of them, named APS1, encoded a protein similar to Rat Arf1p GTPase-activating protein (Arf1p GAP), which has a Cys2/Cys2-type GATA-1-like zinc-finger motif, suggesting that APS1 is a novel member of this class of zinc-finger protein gene family in Arabidopsis. Disruption of the zinc-finger motif in the gene product APS1, however, did not abolish its ability to suppress pde1. Cyclic AMP (cAMP) plays an important signaling role in initiation of sexual development in fission yeast. cAMP is synthesized by adenylate cyclase encoded by the cyr1 gene, and hydrolyzed by cAMP phosphodiesterase encoded by the pde1/cgs2 gene. When the intracellular cAMP level is high, protein kinase A (PKA) is activated by the binding of cAMP to the regulatory subunit, which in turn represses transcription of the ste11 gene encoding a key transcription factor for mating, meiosis and sporulation. A decrease in the cAMP level under poor nutritional conditions triggers ste11 transcription and induces sexual development. Although cAMP is predicted to serve as a second messenger in higher plants, as in many other organisms, the biological significance of cAMP is still largely unknown. To better understand the role of cAMP in higher plants, especially its possible relation to the regulation of sexual development, we previously set out to isolate Arabidopsis cDNAs that could suppress mating-deficiency of the pde1 mutant using transcomplementation. To extend our previous study, we repeated the same screening here. The S. pombe pde1 strain JZ666 was transformed with an Arabidopsis cDNA