| Summary: | Drought stress is a major constraint to the quality and production of <i>Salvia miltiorrhiza</i> Bunge (Danshen). This study aimed to investigate the posttranslational molecular mechanisms in <i>S. miltiorrhiza</i> leaves in response to drought stress using quantitative phosphoproteomics analysis. <i>S. miltiorrhiza</i> plants were stressed by withholding water for two (moderate drought stress) and four weeks (high drought stress). Leaf samples were prepared with tandem mass tag labeling. Liquid chromatography-tandem mass spectrometry was performed for the quantitative phosphoproteomics. Bioinformatics methods were used to identify the phosphosites and phosphoproteins that had significantly changed phosphorylation levels upon drought stresses. A total of 119 common phosphoproteins were significantly changed by both high and moderate drought stresses. The phosphorylation levels of proteins related to protein processing, photosynthesis, RNA binding, and splicing were significantly changed upon high drought, not moderate drought. Additionally, we identified that the Ser phosphorylation levels of most proteins related to terpene metabolism and RNA splicing were regulated by drought stresses. The Ser and Thr phosphorylation levels of energy metabolism proteins (including FBA2/8, PPC4, and PPCC) and heat shock proteins (including HSP70 and HSP90) were upregulated by drought stresses. Our study showed the posttranscriptional mechanisms in <i>S. miltiorrhiza</i> leaves in response to drought stress.
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