The Role of the Ubiquitin-Proteasome System in Agrobacterium tumefaciens-Mediated Genetic Transformation of Plants

Candidate plant gene homologues in grapevine involved in Agrobacterium transformation

“…The tumor formation is a rather complex process that includes the transfer of a well defined DNA segment, called T-DNA, from the prokaryote bacterium into the chromosome of the eukaryote host, its stable integration into the nuclear DNA and expression in the plant cell [2]. While the DNA transport and its nuclear targeting is mediated by bacterial virulence genes, several plant proteins contribute to the integration of T-DNA into the host genome [8,10,11]. Therefore, blocking the expression of contributing plant genes may result in resistance to Agrobacterium transformation [1, 8,11,15,16], providing a potential strategy to engineer disease resistant crop plants.…”

“…While the introduction and nuclear targeting of T-DNA is mediated mainly by bacterial virulence proteins, several plant proteins also contribute to its integration into the plant chromosome [5,[7][8][9][10][11][12][13]. Methods applied to identify plant genes (proteins) involved in crown gall tumorigenesis and Agrobacteriummediated plant transformation include T-DNA tagged mutagenesis of Arabidopsis thaliana [14], virus-induced gene silencing in tobacco [7], yeast two-hybrid system [15,16] and differential gene expression studies on A. thaliana, tobacco or Ageratum conyzoides plants [17][18][19][20].…”

“…Methods applied to identify plant genes (proteins) involved in crown gall tumorigenesis and Agrobacteriummediated plant transformation include T-DNA tagged mutagenesis of Arabidopsis thaliana [14], virus-induced gene silencing in tobacco [7], yeast two-hybrid system [15,16] and differential gene expression studies on A. thaliana, tobacco or Ageratum conyzoides plants [17][18][19][20]. These studies identified approximately 40 plant genes (proteins) which are involved in Agrobacteriummediated transformation including, for example, the Arabinogalactan-Protein AtAGP17, the Reticulon domain proteins (BTI1-3), the VirE2 interacting proteins (Vip1 and Vip2), importins, histones and several other factors involved in the ubiquitin-proteasome complex [reviewed in 10,11]. Inactivation of such genes by insertion mutagenesis or gene silencing resulted in an attenuated tumor phenotype or even resistance to Agrobacterium transformation [7,8,[14][15][16][21][22][23], while their overexpression in transgenic plants increased their Agrobacterium sensitivity [15,24,25].…”

“…For example, the histone H2A-1 gene [26], the F-box protein genes VBF [23], SKP1 and SGT-1 [8] showed elevated levels of expression following inoculation with virulent or transformation competent agrobacteria. Manipulation of these contributing genes may extend the host range of Agrobacterium or result in resistance to crown gall disease [1,11].…”

The role of RAR1 inAgrobacterium-mediated plant transformation

“…This step in the transformation process is not clearly understood, even though the involvement of the host ubiquitin-proteosome system (UPS) has been suggested. 1 One of the most extensively studied UPS in plants includes the SKP1/Cullin/ F-box (SCF) E3 ubiquitin ligase complex which is induced upon Agrobacterium tumefaciens infection 2 and mediates degradation of the cognate proteins either through the induction of a plant specific F-box protein VBF 3 or by the Agrobacterium F-box protein VirF, which is exported into the host cell. 4 The plant SCF complex mediates polyubiquitination of host and foreign proteins for degradation, thus controlling a plethora of biological process within the cell.…”