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Plant Physiology 61:743-747 (1978)
© 1978 American Society of Plant Biologists

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Articles

Indole-3-acetic Acid Synthesis in Tumorous and Nontumorous Species of Nicotiana 1

Shih-Tung Liu, Charles D. Katz and C. Arthur Knight

Department of Molecular Biology, University of California, Berkeley, California 94720

The synthesis of indole-3-acetic acid (IAA) in the enzyme extracts of Nicotiana glauca, Nicotiana langsdorffii, their F1 hybrid, their amphidiploid hybrid, and the nontumorous mutant of the hybrid was investigated. Tryptamine, a possible precursor of IAA biosynthesis in Nicotiana tabacum, was not found in the callus tissue of N. glauca, N. langsdorffii, and their F1 hybrid.

In petiole slices, the synthesis of IAA progressively increased during 5 hours of incubation in [14C]tryptophan. The rate of synthesis was about equal in the hybrid and N. langsdorffii but lower in N. glauca on either a cell or fresh weight basis. It was also found that tryptophan was about 25 times more efficient than tryptamine in promoting synthesis of IAA in petiole slices.

It was found that indoleacetaldehyde oxidase, indoleacetaldehyde reductase, and tryptophan aminotransferase activities were present in all of the species examined; however, tryptophan decarboxylase activity was not found. The tryptophan aminotransferase activity in N. glauca, N. langsdorffii, and the nontumorous mutant required {alpha}-ketoglutaric acid and pyridoxal 5-phosphate whereas the addition of pyridoxal 5-phosphate seemed not to increase the enzyme activity in tumor plants.

The tryptophan aminotransferase in the amphidiploid hybrid was partially purified by acetone precipitation. The enzyme activity had a temperature optimum at 49 C and a pH optimum at 8.9. It is suggested that there is an indolepyruvic acid pathway in the synthesis of IAA in the Nicotiana species examined.

1 This investigation was supported, in part, by National Institutes of Health Research Grant CA 14097 from the National Cancer Institute; a University of California, Berkeley Campus Faculty Research Grant; and Biomedical Sciences Support Grant FR-7006 from the General Research Support Branch, Division of Research Resources, Bureau of Health Professions Education and Manpower Training, NIH.






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Copyright © 1978 by the American Society of Plant Biologists