Enhanced epidemic intelligence using a web-based screening system during the 2010 FIFA World Cup in South Africa

Binary file ES_Abstracts_Final_ECDC.txt matches

Silencing Agrobacterium oncogenes in transgenic grapevine results in strain-specific crown gall resistance

KEY MESSAGE

Grapevine rootstock transformed with an Agrobacterium oncogene-silencing transgene was resistant to certain Agrobacterium strains but sensitive to others. Thus, genetic diversity of Agrobacterium oncogenes may limit engineering crown gall resistance.

ABSTRACT

Crown gall disease of grapevine induced by Agrobacterium vitis or Agrobacterium tumefaciens causes serious economic losses in viticulture. To establish crown gall-resistant lines, somatic proembryos of Vitis berlandieri × V. rupestris cv. 'Richter 110' rootstock were transformed with an oncogene-silencing transgene based on iaaM and ipt oncogene sequences from octopine-type, tumor-inducing (Ti) plasmid pTiA6. Twenty-one transgenic lines were selected, and their transgenic nature was confirmed by polymerase chain reaction (PCR). These lines were inoculated with two A. tumefaciens and three A. vitis strains. Eight lines showed resistance to octopine-type A. tumefaciens A348. Resistance correlated with the expression of the silencing genes. However, oncogene silencing was mostly sequence specific because these lines did not abolish tumorigenesis by A. vitis strains or nopaline-type A. tumefaciens C58.

Incompatibility properties of tartrate utilization plasmids derived from Agrobacterium vitis strains

The incompatibility properties of two tumor-inducing (Ti) and seven tartrate (Tr) plasmids, derived from various Agrobacterium vitis strains, were characterized using incRh1, incRh2, incRh3, and incRh4 clones which were established for the identification and classification of Agrobacterium plasmids. The tested A. vitis plasmids could be allocated into four groups on the basis of their incompatibility with incRh1, incRh2, and incRh4 clones. The two octopine tumor-inducing plasmids, pTiAT6 and pTiAB3, expressed incompatibility both to incRh1 and to incRh2 clones. Three pTrs could not be allocated either to incRh1-4 and incAg1 or to the wide-host-range incP1, incQ, and incW groups.

Physical map of the vitopine Ti plasmid pTiS4

Within the Agrobacterium vitis group the vitopine strains represent a special subclass. Vitopine bacteria carry Ti plasmids with little or no homology with the well-characterized T-DNAs of Agrobacterium tumefaciens or Agrobacterium rhizogenes. The 262-kb Ti plasmid of the vitopine strain S4 was cloned and mapped. Homology studies with the octopine Ti plasmid pTiAch5, the nopaline Ti plasmid pTiC58, and the agropine/mannopine Ri plasmid pRiHRI identified several regions of homology. The origin of replication was localized to within 2.5 kb.

Nucleotide sequence, evolutionary origin and biological role of a rearranged cytokinin gene isolated from a wide host range biotype III Agrobacterium strain

A DNA fragment with homology to the cytokinin (ipt) gene from biotype I Agrobacterium tumefaciens strain Ach5 was cloned from the Ti plasmid of the wide host range biotype III Agrobacterium strain Tm-4 and sequenced. The fragment contains an intact ipt coding sequence. However, the 3' non-coding region of this ipt gene is rearranged due to a 0.9 kb deletion fusing it to the 3' coding region of the neighbouring gene 6a, most of which was found to be deleted. The Tm-4 ipt gene is strongly related to the partially deleted ipt gene of the limited host range biotype III strain Ag162. To test its biological activity, the Tm-4 ipt gene was inserted into a specially constructed, disarmed Ti vector lacking tzs and tested on tobacco, where the rearranged ipt gene induced shoot formation. The cloned Tm-4 ipt gene was mutated with Tn5 and the intact gene on the wild-type Tm-4 Ti plasmid was replaced by the mutated gene. The resulting strain was avirulent on tobacco but normally virulent on the natural host of the wild-type strain Tm-4, grapevine. As the biotype I 6b gene diminishes the effect of a corresponding ipt gene, a larger Tm-4 fragment carrying both the ipt gene and an adjacent 6b-like gene was also tested on tobacco and compared with the Tm-4 ipt fragment alone and with an ipt and 6b/ipt fragment derived from Ach5. The Tm-4 6b gene diminishes the effect of the Tm-4 ipt gene, showing the Tm-4 6b gene to be active as well. The Tm-4 6b/ipt combination is less effective than the Ach5 combination. These results provide further insight into the molecular basis of the host range differences between limited host range and wide host range biotype III Agrobacterium strains and show that the WHR cytokinin gene, although active, does not significantly contribute to tumour formation on the natural host of the WHR biotype III strains, grapevine.