DNA transfer fromAgrobacterium toZea mays orBrassica by agroinfection is dependent on bacterial virulence functions

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Abstract
DNA transfer fromAgrobacterium tumefaciens, a soil bacterium, to the non-host graminaceous monocotyledonous plantZea mays, was analysed using the recently developed technique of agroinfection. Agroinfection ofZ. mays with maize streak virus using strains ofA. tumefaciens carrying mutations in the pTiC58 virulence region showed an almost absolute dependence on the products of the bacterialvirC genes. In contrast, agroinfection of the control hostBrassica rapa with cauliflower mosaic virus was less dependent on thevirC gene products. In other respects, the basic mechanism of the plant-bacterium interaction was found to be similar. While intactvirA, B, D and G functions were absolutely necessary, mutants invirE were attenuated. Agroinfection of maize was effective in the absence of an exogenously suppliedvir gene inducer, and indeed woundedZ. mays tissues were found to produce substance(s) which induced the expression ofA. tumefaciens vir genes. These findings are discussed in the light of current knowledge about the function ofAgrobacterium vir genes.