Combined Transcriptomics and Metabolomics to Analyze the Response of Foxtail Millet Under Salt Stress in Conjunction With Different Soil Amelioration Techniques

Abstract

Soil salinization is a major global issue severely affecting agricultural production and ecosystem balance. Although combining different cultivation techniques can alleviate the harm of salt stress to crops to some extent, the specific metabolic mechanisms by which crops adapt to salt stress remain incompletely understood. This study focuses on uncovering this crucial mechanism and conducts an in-depth exploration by integrating and analyzing the transcriptomic and metabolomic data of foxtail millet (Setaria italica) subjected to salt stress under different combinations of soil amelioration techniques. These results show that the combined application of organic fertilizers and soil amendments significantly enhances the activities of antioxidant enzymes (superoxide dismutase [SOD] and peroxidase [POD]) and promotes the accumulation of osmotic regulators (soluble proteins and proline) in salt-stressed foxtail millet. Moreover, in the soil with biochar added, the content of the flavonoid compound kaempferol increases significantly, while in the soil with only organic fertilizers or soil amendments applied, the content of kaempferol decreases significantly. This study also reveals that the expression patterns of key genes in the flavonoid synthesis pathway are consistent with the accumulation of corresponding metabolites, and a large number of transcription factors are involved in the salt stress response process. These results suggest that under salt stress, different soil amelioration techniques in combination can strengthen the antioxidant defense system and adjust the flavonoid metabolic pathway to enhance the salt-stress resistance of foxtail millet, providing an effective strategy for enhancing crop productivity on saline soils.