A new plant SUMO ligase, MPEL1, synergizes with MAPK16 to regulate resistance against Fusarium pathogens

SUMOylation is critical for plant growth and defense, and the specific substrate recognition mediated by SUMO ligases dictates the biological processes in which SUMOylation functions. However, only four SUMO ligases involved in SUMOylation have been reported in plants. Here, we report MPEL1 as a new SUMO ligase in maize, which paradoxically exhibits SUMO ligase activity despite its sequence homology to SUMO-targeted ubiquitin ligases (STUbL). MPEL1 stabilizes the plant-specific mitogen-activated protein kinase 16 (MAPK16) via SUMOylation at Lys526 within C-terminal domain (CTD). MAPK16 directly binds to JAZ20 via its C-terminal domain and phosphorylates JAZ20 at Thr12/Ser13 residues, thereby triggering its proteasomal degradation and activating broad-spectrum resistance against two Fusarium pathogens. These pathogens cause devastating maize ear rot and stalk rot, leading to severe yield losses and serious food safety concerns worldwide. Notably, MAPK16 overexpression and JAZ20 knockout enhance disease resistance without yield penalty, highlighting their potential for crop improvement. These findings expand the plant SUMO ligase family and provide targets for breeding Fusarium-resistant crops.