Osmotic Regulation of Betaine Content in Leymus chinensis Under Saline-alkali Stress and Cloning and Expression of Betaine Aldehyde Dehydrogenase(BADH) Gene

The potted Leymus chinensis seedlings were treated with saline-alkali solution of six different(from I to VI) concentrations. The results demonstrate that the betaine content and Betaine-aldehyde dehydrogenase(BADH: EC 1.2.1.8) activities have a direct relation with increased stressing time in the same treatment; both exhibit a single peak with increasing the concentration of saline-alkali solution, and number V shows the highest value. The BADH gene of Leymus chinensis was cloned by RT-PCR and RACE technology and was designated as LcBADH. The cDNA sequence of LcBADH was 1774bp including the open reading frame(ORF) of 1521bp(coding 506 amino acids). The vector of prokaryotic expression was constructed by inserting the LcBADH gene fragment into pET30a(+) and transformed into E. coli BL21 (DE3). The result of SDS-PAGE shows that the idio-protein with a molecular mass of 56.78 kDa was effectively expressed in the recombinant bacteria induced by isopropyl β-D-thiogalactoside(IPTG).