Effect of NaCl stress on protein expression of vegetable soybean seed at early filling stage

Under vermiculite culture conditions, vegetable soybean Glycine max (L.) Merr. was treated with 100 mmol/L NaCl at the 10th day after flowering. After the separation of proteins from the seeds at the 5th day of the NaCl stress by two-dimensional gel electrophoresis (2-DE), the differences in protein expression were analyzed between the NaCl treatment and the control. About 327 proteins are detected at each 2-DE map, of which 28 proteins are found to be differentially expressed. Among these NaCl-stress-changed proteins, 16 proteins are up-regulated, while other 12 proteins are down-regulated significantly. Out of the 28 proteins, the abundances of 6 proteins are changed more than 2.5 times. The 6 proteins are analyzed by using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and searched in the database which allows the identification of 5 spots. These identified proteins are Glycinin G2 precursor, actin, similar to GLYCININ G2 PRECURSOR, alpha-tubulin-like protein and Kunitz trypsin inhibitor. The protein metabolisms at early seed-filling of vegetable soybean of the identified proteins are influenced significantly under the NaCl stress, and actin, alpha-tubulin-like protein and Kunitz trypsin inhibitor might be involved in NaCl stress responses.