Enhancement of drought resistance and biomass by increasing the amount of glycine betaine in wheat seedlings

Drought is a major agricultural menace reducing crop productivity and limiting the successful realization of land potential throughout the world. Therefore, breeding common wheat with improved drought-tolerance via genetic manipulation is of great importance. We have introduced the betA gene encoding choline dehydrogenase from Escherichia coli into common wheat (Triticum aestivum L.) by Agrobacterium-mediated transformation. Various levels of expression of the betA gene were confirmed by RT-PCR among the transgenic lines and different levels of glycine betaine accumulation were detected in these lines. Several wheat transgenic lines with different betA expression levels in the T3 generation and wild-type (WT) were selected to test their performance under drought stress conditions. Water deficit in plants caused a reduction in photosynthesis and activity of the PSII complex and resulted in increased accumulation of osmolytes. Drought stress also led to lower membrane stability along with much higher activities of superoxide dismutase and peroxidase in all wheat lines. However, wheat lines that were transgenic for the betA gene were less injured and exhibited greater root length and growth compared with the WT. It was concluded that the amount of injury to the wheat plants was negatively correlated with the level of accumulation of glycine betaine, and the glycine betaine acted as an important osmoprotectant in transgenic plants to improve root growth, and enhance the resistance of transgenic plants to drought stress.