The Effect of Mutations in the T-DNA Encoded Auxin Pathway on the Endogenous Phytohormone Content in Cloned Nicotiana tabacum Crown Gall Tissues

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We analyzed the endogenous auxin and cytokinin levels of cloned Nicotiana tabacum SR1-lines induced either by the wild-type Agrobacterium tumefaciens C58 strain or by mutants affected in the T-DNA-encoded IAA biosynthesis pathway. The wild-type SR1-C58 line contained up to 20 times more IAA than a nontransformed SR1-callus line. The mutant lines affected in gene 1 (iaaM^-) or gene 2 (iaaH^-) contained intermediate levels of IAA. Analysis of the endogenous levels of indole-3-acetamide (IAM) in the nontransformed SRI callus line, the wild-type SR1-C58 and the two mutant lines confirmed the T-DNA-induced IAA biosynthesis pathway in the transformed tumor cells. Supplementing auxin to the mutant lines resulted in complete suppression of the shoot-forming ability, but no changes in the endogenous IAA Ievels. There was no marked difference in the cytokinin level between the non-transformed callus line and the wild type tumor line. The two mutant lines, however, showed a 20- to 30-fold higher cytokinin level which was not affected by the addition of NAA. The T-DNA encoded hormone biosynthetic pathways are discussed in relation to pathways of the host plant.
日本植物生理学会の論文