Molecular cloning of Phosphoethanolamine N-methyltransferase (PEAMT) gene and its promoter from the halophyte Suaeda liaotungensis and their response to salt stress

Phosphoethanolamine N-methyltransferase (encoded by the PEAMT gene) catalyzes the methylation of phosphoethanolamine to produce phosphocholine, which is dephosphorylated to free choline. Choline is the substrate for glycine betaine synthesis, which can improve the salt tolerance of plants. A 1688 bp cDNA of SlPEAMT was isolated from the halophyte Suaeda liaotungensis. Real-time quantitative PCR showed that SlPEAMT expression was induced in S. liaotungensis under salt stress. An 897 bp fragment of the 5′ flanking region of SlPEAMT (designated pP) was isolated from S. liaotungensis. This fragment contained the transcription start site and a number of stress-responsive elements, such as MBS, GT-1 elements, and a W-box. The fragment was inserted into the pCAMBIA1301 plasmid by replacing the CaMV35S promoter. The pP-GUS construct was introduced into tobacco. β-glucuronidase (GUS) histochemical staining and quantitative fluorescence analysis showed an 18.6-fold increase in GUS activity in pP-GUS transgenic tobacco treated with 200 mmol NaCl l−1. Thus, SlPEAMT and its promoter are responsive to salt stress and may be useful in genetic engineering to improve plant salt tolerance.