Molecular cloning and characterization of a novel adenylyl cyclase gene, HpAC1, involved in stress signaling in Hippeastrum x hybridum.

Adenylyl cyclases (ACs) are enzymes that generate cyclic AMP, which is involved in different physiological and developmental processes in a number of organisms. Here, we report the cloning and characterization of a new plant adenylyl cyclases (AC) gene, designated HpAC1, from Hippeastrum x hybridum. This gene encodes a protein of 206 amino acids with a calculated molecular mass of 23 kD and an isoelectric point of 5.07. The predicted amino acid sequence contains all the typical features of and shows high identity with putative plant ACs. The purified, recombinant HpAC1 is able to convert ATP to cAMP. The complementation test that was performed to analyze the ability of HpAC1 to compensate for the AC deficiency in the Escherichia coli SP850 strain revealed that HpAC1 functions as an adenylyl cyclase and produces cyclic AMP. Moreover, it was shown that the transcript level of HpAC1 and cyclic AMP concentration changed during certain stress conditions. Both mechanical damage and Phoma narcissi infection lead to two sharp increases in HpAC1 mRNA levels during a 72-h test cycle. Changes in intracellular cAMP level were also observed. These results may indicate the participation of a cAMP-dependent pathway both in rapid and systemic reactions induced after disruption of symplast and apoplast continuity.