This award provides further funding for Dr. S. F. Yang, to enable him to continue his research on ethylene biosynthesis. Assisted by other NSF-supported younger collaborators, Yang has demonstrated that ethylene is synthesized from methionine via S- adenosylmethionine and 1-aminocyclopropane-1-carboxylic acid. The principal objectives of the project now to be carried out by Dr. Yang are (a) to purify fully and characterize 1- aminocyclopropane-1-carboxylic acid synthase and to determine the amino acid sequence around the active site of this enzyme isolated from apples and other plant tissues, (b) to clone the gene for this enzyme from apples, (c) to characterize the inactivation of the synthase by S-adenosylmethionine in relation to the enzyme's in vivo turnover, and (d) to characterize enzymes involved in the so-called methionine cycle. Ethylene is a plant hormone responsible for the control of numerous aspects of plant growth and development. This hormone is commercially important in agriculture and in relation to post- harvest crop physiology. The work to be pursued here is aimed at obtaining basic knowledge that can later be used as a basis for manipulating the levels of ethylene in plants, either upward or downward. This is a promising approach to optimizing certain agricultural systems. Dr. Yang's studies will provide a useful theoretical basis from which ethylene production by crop plants can be regulated via biotechnology.
