Protein degradation mediated by the ubiquitin-proteasome system (UPS) is involved in many cellular processes in animals and plants.In the UPS,E3 ligases (E3s) are essential for recognizing target proteins and promoting substrate degradation.One E3 ligase,SINA (seven in absentia),which was first identified in Drosophila,is involved in a variety of signaling transduction networks in both animals and plants.Here we discuss recent advances in understanding SlNA-mediated regulation of plant growth and responses to abiotic and biotic stresses.