To identify the residues of OsALDH2B1 phosphorylated by OsSERL1, the in vitro kinase assays were conducted by incubating recombinant MBP-OsSERL1 + MBP-OsALDH2B1 and MBP + MBP-OsALDH2B1. The reaction was terminated by adding SDS loading buffer to a 1×concentration, and the reaction products were subjected to CBB staining and immunoblot analysis as described above. The CBB-stained protein bands corresponding to phosphorylated OsHSFA4d were excised and subjected to LC-MS/MS analysis.