Interactions between Agrobacterium tumefaciens and coniferous defence compounds α‐pinene and trans‐stilbene

Abstract

SummaryThe ability of Agrobacterium species to infect gymnosperms is generally poor, but as a gene transfer vector Agrobacterium would have several advantages. This study characterizes interactions between coniferous defence compounds, a monoterpene α‐pinene and a phenolic constituent trans‐stilbene, and Agrobacterium tumefaciens. Of the chemical constituents studied, α‐pinene in doses equal to the concentrations found in wounded trees prevented the growth of A. tumefaciens. Neither α‐pinene nor trans‐stilbene inhibited virulence gene induction in A. tumefaciens, but both compounds caused a reduction in the frequency of gall formation in susceptible woody model plants (birch seedlings) when applied after the vir‐induction. This effect was smaller with the strain A281(pTVK291) containing extra copies of the virA, virB, virG, and virC genes than with the wild‐type strain A28l. The efficiency of Agrobacterium‐mediated transformation in a model gymnosperm, Scots pine, could not be enhanced by using the strains containing a constitutive mutant of virG gene or extra copies of virA and virG. The results suggest that the inefficiency of Agrobacterium spp. in infecting many conifers is not the result of insufficient vir‐gene induction but rather is the result of interference by chemical defence compounds during the later stages of T‐DNA‐transformation.