Transformation of Poplar Tree with CMO and BADH Genes for Enhancing Tolerance to High Soil Salinity

Choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH) are two enzymes that control synthesis of glycine betaine (GB) in plants. Glycine betaine is an osmoprotentant for maintaining osmotic balance of cells. Research confirmed that exogenous application of GB enhances tolerance of GB non-accumulating plants to abiotic stresses, such as soil salinity, drought, and low temperature.  CMO and BADH genes were individually cloned from Suaeda salsa, a plant grown in the extremely high salt soil and fused together using oligopeptide 2A region from foot-and-mouth disease virus (FMDV). The fused gene (C2AB) successfully co-expressed in yeast and their activities were >40 fold higher than those in the control. In this study, Agrobacterium tumefaciens strain EHA105 that harbored a binary vector (pCAMBIAS1300 and its T-DNA region co-expressing betaine synthase genes) was used to transform an aspen hybrid (Populus × canescens × P. grandidentata). Transformation was primarily confirmed by polymerase chain reaction (PCR). The expression of C2AB fused gene in aspen plants was confirmed using RT-PCR. These transgenic lines are being cloned in vitro and will be further evaluated for salt tolerance under both in vitro and ex vitro conditions. This research shows a great potential to improve abiotic stress tolerance of poplar, an important tree species for the forestry industry and biomass production.