Molecular cloning of a stress-responsive aldehyde dehydrogenase gene ScALDH21 from the desiccation-tolerant moss Syntrichia caninervis and its responses to different stresses.

Aldehyde dehydrogenases (ALDHs) are key enzymes of abiotic stress-tolerance in a variety of organisms. The ALDH gene superfamily in eukaryotes has identified 22 protein families based upon sequence identity. ALDH21 is unique to mosses and represented by a single transcript gene in the desiccation-tolerant moss Tortula ruralis. We describe the cloning and characterization of an ALDH21 homologue from Syntrichia caninervis (ScALDH21), an extremely desiccation-tolerant moss found in deserts of Central Asia. The ScALDH21 cDNA is 1,452 bp and encodes a deduced polypeptide of 483 amino acids (53 kDa), approximately 97% identical to T. ruralis ALDH21 (TrALDH21A). The ScALDH21 gene was subcloned into pET26b(+) and expressed in Escherichia coli (Rosetta) to determine the peptides function in response to desiccation and salinity. Quantitative RT-PCR was used to analyze steady-state mRNA amounts in response to Abscisic acid (ABA) and desiccation. ScALDH21 transcript levels increased significantly in response to both desiccation and ABA. In the transgenic E. coli, ScALDH21 protein could be induced under the salinity and desiccation stress and was more abundant within salt-treated gametophores relative to control tissue. The data suggest that ScALDH21 participates in the stress-resistant pathways and plays an important role in response to desiccation and salinity stresses.