Elucidation of the O-chain structure from the lipopolysaccharide of Agrobacterium tumefaciens strain C58

Agrobacterium strains and strain improvement: Present and outlook

Almost 40 years ago the first transgenic plant was generated through Agrobacterium tumefaciens-mediated transformation, which, until now, remains the method of choice for gene delivery into plants. Ever since, optimized Agrobacterium strains have been developed with additional (genetic) modifications that were mostly aimed at enhancing the transformation efficiency, although an optimized strain also exists that reduces unwanted plasmid recombination. As a result, a collection of very useful strains has been created to transform a wide variety of plant species, but has also led to a confusing Agrobacterium strain nomenclature. The latter is often misleading for choosing the best-suited strain for one's transformation purposes. To overcome this issue, we provide a complete overview of the strain classification. We also indicate different strain modifications and their purposes, as well as the obtained results with regard to the transformation process sensu largo. Furthermore, we propose additional improvements of the Agrobacterium-mediated transformation process and consider several worthwhile modifications, for instance, by circumventing a defense response in planta. In this regard, we will discuss pattern-triggered immunity, pathogen-associated molecular pattern detection, hormone homeostasis and signaling, and reactive oxygen species in relationship to Agrobacterium transformation. We will also explore alterations that increase agrobacterial transformation efficiency, reduce plasmid recombination, and improve biocontainment. Finally, we recommend the use of a modular system to best utilize the available knowledge for successful plant transformation.

Lipopolysaccharides in Rhizobium-legume symbioses

The establishment of nitrogen-fixing symbiosis between a legume plant and its rhizobial symbiont requires that the bacterium adapt to changing conditions that occur with the host plant that both promotes and allows infection of the host root nodule cell, regulates and resists the host defense response, permits the exchange of metabolites, and contributes to the overall health of the host. This adaptive process involves changes to the bacterial cell surface and, therefore, structural modifications to the lipopolysaccharide (LPS). In this chapter, we describe the structures of the LPSs from symbiont members of the Rhizobiales, the genetics and mechanism of their biosynthesis, the modifications that occur during symbiosis, and their possible functions.

Structural Characterisation of the Core Oligosaccharides Isolated from the Lipooligosaccharide Fraction ofAgrobacterium tumefaciens A1

Three different oligosaccharide structures from the lipooligosaccharide fraction of Agrobacterium tumefaciens strain A1 were determined by means of chemical and spectrometrical methods. The peculiar feature of this oligosaccharide family consisted of its unusual length, that was very close to the that minimal requested for the external membrane functionality as exemplified from oligosaccharide 3, where the inner core is glycosylated from only one sugar moiety onwards.

Elucidation of two O-chain structures from the lipopolysaccharide fraction of Agrobacterium tumefaciens F/1

Agrobacterium tumefaciens F/1 produces two different O-chains, both are constituted of rhamnose and glucosamine: the less abundant has a linear disaccharidic repeating unit 3)-alpha-L-Rhap-(1-->3)-beta-D-GlcpNAc-(1--> and the second one 4)-alpha-L-Rhap-(1-->3)-beta-D-GlcpNAc-(1-->. The two intact antigenic moieties were studied in mixture by 2D NMR. Additional supporting data were obtained by periodate degradation, the major component was cleaved selectively, leading to a glucosamine glycoside, whereas the minor one was recovered unaffected.