The ACC Synthase Gene

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The mechanism of induction of ACC synthase, the key regulatory enzyme in the ethylene biosynthetic pathway in plants, by various plant hormones and environmental stimuli is poorly understood. Recent experimental evidence obtained in Dr. Theologis' lab with DNA sequences complementary to the ACC synthase mRNA from zucchini indicate that enzyme inducers such as IAA, wounding Li ions act at the transcriptional or posttranscriptional level. Studies on the structure and regulation of ACC synthase gene(s) in zucchini and tomato are proposed to gain insight into the details of the biochemical mechanism that regulates their expression by various hormones and stress conditions as well as on their role in regulating plant senescence. The specific aims of this proposal are: 1) Isolation and structural characterization of complementary and genomic sequences to ACC synthase mRNA from zucchini and tomato, 2) Developmental regulation of ACC synthase gene expression during growth, 3) Determination of this cis acting DNA regulatory elements that are involved in ethylene and auxin regulated ACC synthase gene expression, 4) Regulation of expression of ACC synthase gene(s) in vivo and in isolated nuclei in response to various hormones and environmental stress conditions, 5) Inhibition of ethylene induced fruit ripening and anaerobiosis-induced epinasty with ACC synthase antisense constructs. %%% Ethylene is one of the simplest organic molecules with biological activity. It is considered to be the fruit ripening hormone known to regulate many aspects of plant growth, development and senescence. ACC synthase is the key enzyme in the synthetic pathway of ethylene.