Osa Protein Constitutes a Strong Oncogenic Suppression System That Can Block vir -Dependent Transfer of IncQ Plasmids between Agrobacterium Cells and the Establishment of IncQ Plasmids in Plant Cells

Abstract

The osa (oncogenic suppressive activity) gene of the IncW group plasmid pSa is sufficient to suppress tumorigenesis by Agrobacterium tumefaciens. osa confers oncogenic suppression by inhibiting VirE2 protein export. This result is similar, but not identical, to that of oncogenic suppression by the IncQ plasmid RSF1010. We conducted a series of experiments to compare oncogenic suppression by these two systems. Agrobacterium strains harboring plasmids containing osa are more able to effect oncogenic suppression than are similar strains containing various RSF1010 derivatives. When osa is present within a donor Agrobacterium strain that also carries a derivative of RSF1010, the transfer of RSF1010 derivatives to recipient bacteria and their establishment in plants are blocked. Oncogenic suppression is still effected when the osa gene is integrated into the Agrobacterium chromosome, suggesting that it is the osa gene product that is active in suppression and that suppression does not require a protein-nucleic acid intermediate like that described for IncQ plasmids. Extracellular complementation experiments with tobacco leaf disks indicated that Osa blocks stable transfer of RSF1010 to plant cells by inhibiting transfer of VirE2, which is essential for the transfer of RSF1010 into plant cells, and not by inhibiting the actual transfer of RSF1010 itself. Our results suggest that Osa and RSF1010 cause oncogenic suppression by using different mechanisms.

Agrobacterium tumefaciens oncogenic suppressors inhibit T‐DNA and VirE2 protein substrate binding to the VirD4 coupling protein

“…Osa also inhibits conjugative transfer of pML122 to agrobacterial recipients (Fig. 6A; Lee and Gelvin, 2004). As assessed by QTrIP, Osa interfered with pML122 binding to the VirD4 receptor without further negative effects on substrate binding to the VirB subunits, as illustrated for VirB9 (Fig.…”

T-DNA Binary Vectors and Systems

“…Different origins of replication replicate to different extents in Agrobacterium. The pSa origin replicates to two to four copies per cell (Lee and Gelvin, 2004), the RK2 and pVS1 (L.-Y. Lee, unpublished data) origins replicate to seven to 10 copies per cell, and the pRi origin replicates to 15 to 20 copies per cell (L.-Y.…”

Novel Plant Transformation Vectors Containing the Superpromoter

“…Over approximately the past 10 years, our laboratory has distributed the various superpromoter constructions to dozens of laboratories. In our laboratory, the superpromoter has routinely and effectively been used to drive both transient and stable transgene expression in tobacco plants and Bright Yellow-2 cell suspensions (Ni et al, 1995;He et al, 1996;Narasimhulu et al, 1996;Kononov et al, 1997;Mysore et al, 1998;Veena et al, 2003;Lee and Gelvin, 2004), Arabidopsis (Arabidopsis thaliana) plants and cell suspensions (Nam et al, 1997(Nam et al, , 1998(Nam et al, , 1999Mysore et al, 2000;Yi et al, 2002;Zhu et al, 2003;Gaspar et al, 2004;Hwang and Gelvin, 2004;Hwang et al, 2006;Crane and Gelvin, 2007;Kim et al, 2007), maize plants and BMS cell suspensions (Narasimhulu et al, 1996), and Brassica napus plants (S. Johnson and S.B. Gelvin, unpublished data).…”