Taxol productivity and physiological relationships in suspension cultures of Taxus Cuspidata
Date
1995
Authors
Mirjalili, Noushin, author
Linden, Jim C., advisor
Reardon, Kennete F., committee member
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Abstract
Taxol, an extractive of the Pacific yew, is a plant secondary metabolite that has demonstrated anticancer activity. In an effort to prevent depletion of Pacific yew population and to obtain adequate supplies of taxol, alternative methods of production are being sought. The goal of this research was to produce taxol in sufficient quantities for clinical use by manipulating engineering parameters that affect production of secondary metabolites in plant cell culture systems. Production of taxol in suspension cultures of Taxus cuspidata in shake flasks exposed to different concentrations and combinations of oxygen, carbon dioxide, and ethylene was investigated. The effect of each gas on cell growth and taxol production was studied using several sets of factorial design experiments. Low head space oxygen con-centration (10% v/v) promoted production of taxol prior to day 14. High carbon dioxide concentration (10% v/v) inhibited taxol production. Taxol concentration increased as ethylene concentration was increased to 5 ppm; it leveled at 10 ppm ethylene. The utilization patterns of sugars were dependent on headspace gas composition. Average calcium uptake rates into the cultured cells decreased and average phosphate uptake rates increased as the ethylene concentration was in-creased from 0 to 10 ppm. Ethylene concentration at 50 ppm had an inhibitory effect on taxol production but not on phosphate uptake rate, suggesting independent regulation of taxol biosynthesis and physiological functions of the cell. The most effective gas mixture composition tested in terms of taxol production—10% (v/v) oxygen, 0.5% (v/v) carbon dioxide, and 5 ppm ethylene—is thought to be related to regulation of gene transcription. To stimulate taxol production, suspension cultures of Taxus cuspidata were challenged with various concentrations and combinations of methyl jasmonate (an elicitor derived from jasmonic acid) and ethylene. Taxol productivity increased 19-fold compared to the basal level when Taxus cuspidata suspension cultures were exposed to 5 ppm ethylene and 10 μM methyl jasmonate. The induction of taxol biosynthesis occurred within 51 hours after elicitation. Simple induction models were proposed to explain the action and effects of both ethylene and methyl jasmonate with regard to receptor binding and transcription regulation in plants.
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Subject
Paclitaxel
Plant cell culture
Taxus