Arabidopsis lines expressing 35S::Strep-SUMO1H89R in Col-0 background were generated since the H89R SUMO1 variant simplifies MS/MS detection of SUMO conjugated lysines after trypsinization (Miller et al., 2010). Transgenic seedlings were treated with water or 250nM flg22 for 30 minutes and total protein extracts including membrane fractions were affinity purified with Pierce™ Streptavidin Magnetic Beads. LC-MS analysis of eluting proteins allowed identification of candidate SUMO-conjugated proteins in response to flg22 treatment.