Regulation of ACC Synthase Protein Stability

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The gaseous hormone ethylene has profound effects on plant growth and development. The rate-limiting and key regulatory step in the biosynthesis of this hormone is catalyzed by ACC synthase (ACS). Previous studies have shown that the C-terminal domain of ACS targets this protein for rapid degradation, and several factors involved in regulating this degradation have been identified. The primary goal of this research is to further elucidate the mechanisms regulating ACS protein turnover. To these ends, the following lines of investigation will be pursued: 1) The role of protein phosphorylation in controlling ACS protein stability will be examined, and the precise portion of the ACS protein required for its rapid degradation will be delineated; 2) The stability of ACS protein during various developmental events that are associated with a rise in ethylene biosynthesis or in response to exogenous cues will be examined to determine if altered ACS protein stability plays a role in controlling ethylene biosynthesis under these conditions; 3) The role that two Arabidopsis DnaJ (a.k.a. HSP40) orthologs play in regulating ACS turnover will be studied; 4) The CIN2 gene, which was previously identified as a gene that is involved in controlling ethylene biosynthesis, will be cloned and characterized; 5) A genetic screen will be performed to identify novel elements involved in regulating ACS protein turnover. These studies will shed light on the mechanism regulating the stability of ACS proteins and how this contributes to the control of the biosynthesis of ethylene. This research will also increase our understanding of the role of DnaJ in higher eukaryotic organisms, and on the mechanism by which this ubiquitous protein acts.Results from these studies will lead to a deeper understanding of the regulation of ethylene biosynthesis, which may lead to the ability to manipulate the production of this hormone in an agricultural setting and hence improve the quality and longevity of various agricultural products. Furthermore, the regulation of protein turnover has emerged as a central mechanism underlying a variety of biological systems. This research will shed light on this fundamental process and enhance the infrastructure of research and education by providing hands-on training for undergraduate students, graduate students, and post-doctoral researchers. In addition, it will also allow collaboration with the DESTINY Traveling Science Learning Program to assist in the creation and maintenance of a plant based learning module aimed at fostering science education in grades K-12.