alpha-dl-Difluoromethylornithine, a Specific, Irreversible Inhibitor of Putrescine Biosynthesis, Induces a Phenotype in Tobacco Similar to That Ascribed to the Root-Inducing, Left-Hand Transferred DNA of Agrobacterium rhizogenes.

alpha-dl-Difluoromethylarginine (DFMA) and alpha-dl-difluoromethylornithine (DFMO), specific irreversible inhibitors of putrescine biosynthesis were applied to Nicotiana tabacum var. Xanthi nc during floral induction. DFMO, but not DFMA, induced a phenotype in tobacco that resembles the transformed phenotype attributed to the root-inducing, left-hand, transferred DNA of Agrobacterium rhizogenes, including wrinkled leaves, shortened internodes, reduced apical dominance, and retarded flowering. Similar treatment of transformed plants (T phenotype) accentuated their phenotypic abnormalities. Cyclohexylammonium and methylglyoxal bis (guanylhydrazone), inhibitors of spermidine and spermine biosynthesis, produced reproductive abnormalities, but did not clearly mimic the transformed phenotype. This work strengthens the previously reported correlation between the degree of expression of the transformed phenotype due to the root-inducing, left-hand, transferred DNA and inhibition of polyamine accumulation, strongly suggesting that genes carried by the root-inducing, transferred DNA may act through interference with polyamine production via the ornithine pathway.