Update information publication. To identify the phosphorylation site of ZmRR1 by ZmMPK8 in vitro, 10 µg GST-ZmRR1 and 1 µg His-ZmMPK8 purified proteins were incubated in 20 µl of protein kinase reaction buffer containing 20 mM MgCl2, 50 mM Tris-HCl pH 7.5, 1 mM DTT, and 50 µM ATP, at 30°C for 30 min. The reaction products were reduced by DTT and alkylated by IAM (Iodoacetamide), followed by digestion with trypsin (pH 8.5) at 37°C for 12 h. The results were analyzed by LC-MS/MS