Identification of Plant Factors Inducing Virulence Gene Expression in Agrobacterium tumefaciens.

In the natural gene-transfer system of Agrobacterium tumefaciens, the expression of virulence (vir) gene of Ti (tumor inducing) plasmid is essential for the subsequent transferred deoxyribonucleic acid (T-DNA) transfer from bacterium to plant cells. vir gene expression is induced by signal compounds from pants such as acetosyringone and α-hydroxyacetosyringone which were isolated from hairy root cultures of Nicotiana tabacum. In a search for intrinsic signal compounds in plants, acetosyringone and α-hydroxyacetosyringone were identified as the vir-inducing compounds of the hairy root cultures of Atropa belladonna. The signal compounds of seedlings of Pisum sativum were identified as sinapyl and coniferyl alcohols. The quantities of these vir-inducing compounds were significantly increased when plant tissues were wounded, though the degree of increase was markedly different in each plant.