Construction of Co-expressing Vector for Gly Bet Synthesis and Salt Tolerance

Glycine betaine (GlyBet) is an established target for metabolic engineering of stress tolerance because it is a potent osmoprotectant that many plants lack. GlyBet is synthesized in the chloroplast by a two-step oxidation of choline (Cho) that is catalyzed by CMO and BADH. Cho is one of essential precursors for the synthesis of GlyBet. PEAMT is a key enzyme in the Cho biosynthetic pathway and serves as a step-limiting controller. The CMO cDNA and BADH cDNA drived by 35S and the PEAMT genomic DNA were cloned into the binary vector(pCAMBIA1300) containing HPTⅡgene step by step. The plasmid was checked by 7 enzymes, and the fingerprints were expected. The plasmid of this expressing vector was transferred into the Agrobacterium tumefaciens (GV3101) by electroporation, then used in genetic transformation of A. thaliana mediated by vacuum infiltration. The primary transgenic plants were selected for hygemycin resistance and verified by PCR. The transgenic lines showed less growth inhibitation than control on 1/2MS containing 125 mmol·L-1 NaCl.