Richard N. Arteca - US grants

Ethylene is a plant growth regulator with potent effects throughout plant growth and development, from seed germination through fruit ripening and senescence and death of the plant. Other plant hormones affect the key regulatory step leading to the synthesis of ethylene in plants. Thus, the biosynthesis of ethylene presents a very complicated picture. The enzyme which carries out the final biosynthetic step is present in extremely small amounts and has eluded expert plant biochemists for years. This project funds a short term project to purify and identify this key plant enzyme. Both the phytohormones indole-3-acetic acid and brassinosteroid specifically affect the conversion of S- adenosylmethionine (SAM) to 1-aminocyclopropane-1-carboxylic acid (ACC), the key reaction controlling the production of ethylene. Despite ethylene's role in diverse plant physiological processes, the major features of control of its formation from SAM via ACC within the plant and how it acts have not been established. The study of ACC synthase (the rate limiting enzyme which catalyzes the reaction between SAM and ACC) and how phytohormones affect its level in tissues have been hampered by the inability to obtain purified enzyme and thus be able to detect specific changes in mRNA formation or stability which could account for the elevation in ACC synthase activity. This study focuses on the further development of the present purification scheme for obtaining purified enzyme and also to characterize it. The enzyme being purified is ACC synthase from etiolated mung bean hypocotyl tissue which has been hormonally treated to elevate enzyme levels. Purification will involve chromatography on phenyl sepharose, hydroxylapatite and anion exchange columns. The purified enzyme will be characterized by denaturing gel electrophoresis and isoelectric focusing. Kinetic properties and coenzyme content will also be analyzed. Once this project is complete to study the regulation of ACC synthase can be attempted and how other plant hormones affect transcriptional control of this key enzyme can be learned.***//

This symposium provides an up-to-date assessment of our knowledge of the biosynthesis, metabolism and molecular biology of polyamines and ethylene. Presentations by outstanding researchers in the field will provide a critical analysis of the involvement of polyamines and ethylene in plant growth, development, and responses to stress. The antagonistic roles of these molecules in senescence, plant stress and development will be examined, as well as the possible regulatory mechanisms for the ethylene and polyamine pathways. Polyamines and ethylene are the two important topics that will be discussed during the 5th Annual Penn State Symposium in Plant Physiology. Polyamines are compounds that have been implicated as markers for male fertility and in flower development. Evidence also suggests that polyamines may retard senescence. Ethylene has been shown to play an important regulatory role in many physiological processes including sex expression, flower initiation and the promotion of senescence. The purpose of this symposium is to address a variety of topics on polyamine and researchers working on these two distinct yet overlapping subjects and provide a catalyst for innovative approaches in the future. The symposium will provide students and post doctoral fellows an unusual opportunity to meet and interact in a small group setting with the leaders in this research area. The published proceedings will provide an up-to-date review of research in these rapidly advancing fields which will be of general value to students and scientists in colleges and universities, government, and industry.