Dr. Yoon’s research interest lies in understanding of the molecular mechanisms of the key steps in the phytohormone ethylene biosynthesis and its signaling pathway using the model plant Arabidopsis thaliana. The gaseous hormone ethylene regulates many important plant growth and developmental processes, including fruit ripening, seed germination, nodulation, senescence and response to a variety of developmental and environmental stresses.
Two main research projects are currently under way in the lab. First is to investigate the molecular mechanism regulating protein turnover in ethylene biosynthesis. Specifically, we are aiming to understand the molecular mechanism which controls the protein turnover of the 1-aminocyclopropane-1-carboxylic acid synthase (ACS), a key enzyme in the ethylene biosynthesis and the Ethylene Overproducer 1 (ETO1)/ETO1-like (EOL) proteins, ubiquitin ligases that target a subset of ACS for degradation. Secondly, we are focusing on the elucidation of the roles of Constitutive Triple Response 1 (CTR1), a Raf-like protein kinase that acts as a negative regulator, in the ethylene signaling pathway. Ethylene is perceived by receptors that reside at the endoplasmic reticulum membrane (ER) and negatively regulate the ethylene response pathway; this negative regulation is relieved upon binding of ethylene to the receptors. While the elements in the ethylene signaling pathway have been identified, the detailed mechanisms underlying their function and several fundamental questions still remain to be explored. Among many remaining questions, our lab is interested in exploring following questions: 1) how do the ethylene receptors activate CTR1 in the early step of the ethylene signaling pathway?; 2) how does the ethylene response induced by EIN2, the positive regulator in the pathway, is turned off in the nucleus?; 3) and what are the roles of CTR1 other than phosphorylating EIN2 at the ER? We use the combination of biochemistry, genetics, cell biology and molecular biology approach to address these questions.