Our focus is on understanding the genetic and molecular mechanisms that control plant development and physiological response to environmental stresses. We are particularly interested in the regulatory role of the ubiquitin proteasome system (UPS), which effectively controls the abundance of numerous proteins and is essential for many aspects of plant biology. Ubiquitin-dependent degradation involves two distinct and successive steps: (1) attachment of a polyubiquitin chain to the target protein (ubiquitination) and (2) degradation of the ‘tagged’ protein by the 26S proteasome, a multimeric multiproteolytic complex. Target protein selection is governed by a large family of ubiquitin ligases (E3s). We are interested in the function of the Ankyrin-repeat containing RING-type E3s (KEG, XBAT31-35), which include regulatory roles in abscisic acid (ABA) signaling, ethylene production, iron deficiency response, cell death and pathogen defense.