ABSTRACT
The role of plant vitronectin-like protein (Vn) in Agrobacterium-host plant interactions and receptor-specific bacterial attachment is unclear and still open to debate. Using a well-established Agrobacterium-mediated Arabidopsis transformation system, the marker gene beta-glucuronidase (GUS) of Escherichia coli, and biochemical and cytological methods, such as ELISA tests, immunoblots, immunolocalization, and functional in vitro binding assays, we have reassessed the role of Vn in receptor-specific bacterial attachment and transformation. We provide evidence that Vn is present in the host plant cells and anti-human vitronectin antibody cross-reacts with a 65-kDa protein from Arabidopsis cells. The specificity of the immunological cross-reactivity of anti-vitronectin antibodies was further demonstrated by ELISA competition experiments. Immunogold labeling showed that Vn is localized in the plant cell wall, and its level increased considerably after phytohormone treatment of the petiole explants. However, Agrobacterium attachment was unaffected, and no inhibition of petiole cell transformation was detected in the presence of human vitronectin and anti-vitronectin antibodies in the media. Additionally, no correlation between the occurrence of Vn, attachment of bacteria to the cells, and susceptibility to Agrobacterium-mediated transformation was observed. Taken together, our data do not support a functional role of plant Vn as the receptor for site-specific Agrobacterium attachment leading to the transformation of Arabidopsis cells.
Subject(s)
Agrobacterium tumefaciens/physiology , Arabidopsis/genetics , Bacterial Adhesion , Cell Wall/metabolism , Transformation, Genetic , Vitronectin/metabolism , Agrobacterium tumefaciens/metabolism , Agrobacterium tumefaciens/ultrastructure , Arabidopsis/cytology , Arabidopsis/ultrastructure , Cell Wall/ultrastructure , Microscopy, Immunoelectron , Transfection , Vitronectin/geneticsABSTRACT
O-Aryl-d-glucoside (4-7) and d-xyloside (8-10) derivatives were synthesized and tested on Agrobacterium virH gene induction and plant transformation. alpha- or beta-Glycosides enhanced vir activity at concentrations above 250 micromicro. The highest vir activity was observed with beta-glucoside derivative 4 at 10 mM. A marked difference between phenol glucoside derivative 4 and the corresponding free phenol on the growth of transformants was observed. The regenerated transgenic tissues, after transformation on medium containing acetosyringyl beta-glucoside 4, grew at twice the rate of those on medium containing only free acetosyringone (AS). Compound 4 was less toxic for tobacco explants compared to the corresponding free phenol. However, the xyloside derivatives tested (8-10) were less effective for gene induction compared with corresponding free phenols.