Cloning and expression analysis of GADH small subunit gene ga2dh from Serratia sp. NDW3

Objective To clone and identify GADH small subunit gene ga2dh.

Method Changes in soluble phosphorus content, GADH activity and ga2dh gene expression level during the phosphate solubilizing process of Serratia sp. NDW3 from rice rhizosphere were studied. The ga2dh gene was cloned and expressed in Escherichia coli BL21, and bioinformatic analysis was performed.

Result The relative expression of ga2dh gene in the process of phosphate solubilizing by Serratia sp. NDW3 reached maximum at 12 h, GADH activity reached maximum at 24 h, and the soluble phosphorus content stabilized after 36 h. The ga2dh gene sequence of 781 bp was obtained from Serratia sp.NDW3 by cloning. The similarity between ga2dh gene and Serratia sp. SCBI sequences was 99.62% based on bioinformatic analysis. The protein encoded by ga2dh belonged to the superfamily of gluconate dehydrogenase subunit 3 and was composed of three α-helices. The amino acid sequence was consisted of intracellular, extracellular and transmembrane regions. The expression of ga2dh gene in E.coli BL21 significantly increased GADH activity.

Conclusion The main mechanism of phosphate solubilizing by Serratia sp. NDW3 is through the direct oxidation pathway. The small subunit encoded by ga2dh gene not only plays an important role in GADH activation, but also is part of the transmembrane structure of GADH.