Silicon Application Alleviates Drought Stress in Wheat Through Transcriptional Regulation of Multiple Antioxidant Defense Pathways

Silicon (Si) has been shown to increase plant stress tolerance. However, the molecular mechanisms underlying the effects of Si in alleviating drought stress in winter wheat are unknown. The aim of this study was to investigate the effects of Si on photosynthetic pigments, antioxidant contents, and transcription of several genes involved in the antioxidant defense pathway in drought-stressed wheat plants. Si application resulted in higher leaf chlorophyll content, and lower lipid peroxidation levels and H2O2 contents in wheat flag leaves compared with untreated plants. In addition, Si increased the contents of ascorbate (ASC), reduced glutathione (GSH), and the total phenolic and total flavonoid contents in wheat flag leaves. Quantitative real-time PCR was used to analyze gene expression patterns for three antioxidant enzyme genes, four ASC-GSH cycle genes, and five flavonoid biosynthesis pathway genes. Si application increased the expression of these genes in drought-stressed wheat compared with the-Si treatments. Elevated levels of gene expression and low malondialdehyde and H2O2 contents indicate that Si plays a pivotal role in the coordinated transcriptional regulation of multiple antioxidant defenses in response to drought. Our work also suggests that Si may be important in the metabolic or physiological activities for growth and development of winter wheat.