Abstract
Adenosine 3', 5'-cyclic monophosphate (Cyclic AMP; cAMP) is a ubiquitous signalling intermediate that regulates many intracellular processes in living organisms. Adenylyl cyclases (ACs) catalyze the formation of cAMP from adenosine 5'-triphosphate (ATP). The Arabidopsis genome contains two AC genes that have conserved amino-terminal nucleotide-binding domains and show sequence similarity to maize AC, PsiP. Expression of AC1 and AC2 complemented the E.coli AC-deficient mutant, cya, suggesting that both proteins produce functional cAMP in vivo. Gene expression studies using RT-PCR and promoter-GUS staining showed that AC1 is expressed in root tips, inflorescences and anthers, while AC2 is expressed in stems, roots, cauline leaves, senescing leaves and also in inflorescences. T-DNA insertion mutants of AC1 and AC2 showed a delay and a reduction in germination under salt stress. Conversely, overexpression of AC1 and AC2 conferred tolerance against salt stress. Taken together, these results suggest a role for AC1 and AC2 in salinity tolerance via cAMP.
