Enhanced cold stress tolerance of transgenic Dendrocalamus latiflorus Munro (Ma bamboo) plants expressing a bacterial CodA gene

Ma bamboo (Dendrocalamus latiflorus Munro) is a widespread culm and shoot-producing species in southern China. However, low temperatures reduce Ma bamboo shoot production and delay its development. In an attempt to enhance its cold-tolerance, a bacterial CodA gene encoding choline oxidase was introduced into Ma bamboo by Agrobacterium-mediated transformation, an approach that had not been previously utilized in bamboo. PCR and Southern blot analyses confirmed that CodA had integrated into the Ma bamboo genome. RT-PCR results showed that expression of CodA driven by the Arabidopsis Rd29A promoter was induced by cold stress in the transgenic bamboo lines. Following treatment at 4°C for 24 h, the content of glycine betaine (GB) increased to 83% and 140% in control plants (wild type (WT)) and CodA transgenic Ma bamboo plants, respectively. Superoxide dismutase, peroxidase, and catalase activities increased in both transgenic and WT plants. However, increases in these enzymes activities were much greater in the transgenic lines than in the WT plants under cold stress. The accumulation of malondialdehyde and electrolyte leakage (REL) in CodA transgenic Ma bamboo plants was less than that in control plants. Collectively, these results suggest that increased cold-tolerance induced by accumulation of GB in vivo was associated with the enhancement of antioxidant enzyme activities, which led to reduced accumulation of reactive oxygen species and stabilization of membrane integrity against extreme temperatures in transgenic plants.