Early Changes in S-Nitrosoproteome in Soybean Seedlings Under Flooding Stress

The shift from aerobic to anaerobic respiration is crucial for soybean response to flooding stress; however, the regulatory mechanism in action at the initial stage of flooding stress has not been fully elucidated. To identify this mechanism in soybean, proteomic analysis of S-nitrosylated proteins was performed with emphasis on nitric oxide (NO)-mediated regulation in soybean seedlings. Removal of NO by addition of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) partially restored seedling growth. After 3, 9, and 24 h of flooding stress, the S-nitrosylation status of 364, 188, and 186 proteins was altered relative to the corresponding status before flooding, respectively. Abundance of S-nitrosylated forms of 2, 186, and 162 proteins differed between the untreated control and flooded soybean plants after 3, 9, and 24 h of flooding stress, respectively. After flooding for 3 h, development, stress, and glycolysis/fermentation categories were identified as the top categories including proteins for which abundance of S-nitrosylated forms increased. Visualization of changes in S-nitrosylation profile by pathway mapping indicated a characteristic pattern in glycolysis/fermentation. Western blot analysis confirmed that S-nitrosylated status of alcohol dehydrogenase increased with flooding. These results suggest that S-nitrosylation comprises rapid molecular processes that change the abundance of the active form of alcohol dehydrogenase.