Agrobacterium-Mediated Transfer and Stable Incorporation of Foreign Genes in Plants

  • Clarence I. Kado


The transfer of genetic material between a prokaryotic organism to eukaryotic organisms represent a unique phenomenon in biology. The Agrobacterium-mediated gene transfer to plants is the classic example of such a phenomenon. The genes required for this transfer are located on a 200-kbp Ti plasmid. As illustrated in Figure 9.1, a specific sector (the T-DNA) of the Ti plasmid is the element transferred. The 25-kbp T-DNA is bordered by 23-bp directly repeated sequences termed left and right borders. These borders are the targets where specific cleavages occur to generate T intermediates in the Agrobacterium cell. The T intermediates are transferred by still unknown mechanisms to plant cells during infection of the host at wounded sites. A prerequisite for the transmission of the T intermediates is the close interaction of the bacterial cells with the plant cells. Plant signals in the form of phenolic compounds generated by phenylalanine ammonia lyase- and tyrosine ammonia lyase-initiated lignin biosynthetic pathways are recognized by A. tumefaciens through a sophisticated two-component gene regulatory system (recently reviewed in 38). This regulatory system operates through the products of two virulence genes: virA and virG These genes are part of a six-operon vir regulon on the Ti plasmid (52). On recognition of the plant signal, transcription of the normally silent operons is initiated through the signal transduction pathway. Specific gene products of the vir regulon catalyze events that lead to the generation of T-intermediates and to their efficient transfer into the plant host cell. Once entered, the T-DNA is processed for eventual integration into one or more of the chromosomes of the host cell.


Agrobacterium Tumefaciens Crown Gall Bordetella Pertussis Conjugal Transfer Crown Gall Tumor 
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Copyright information

© Springer Science+Business Media New York 1993

Authors and Affiliations

  • Clarence I. Kado
    • 1
  1. 1.Davis Crown Gall Group, Department of Plant PathologyUniversity of California, DavisDavisUSA

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