A preliminary investigation into how plant growth promoting rhizobacteria can influence the frequency of gene transfer in agrobacterium- and transbacter-mediated transformation systems

Agrobacterium-mediated transformation of plants has proven to be the dominant technology in the genetic engineering of plants and until recently, was widely considered to be the only genus capable of such transfer. The complexity of the patent landscape surrounding the use of Agrobacterium has led to the search for other bacterial genera capable of gene transfer. In 2005, members of several bacterial genera were made competent for gene transfer to plants, albeit at low levels. In this study, we have shown that PGPRs can effect the rate of gene transfer to tobacco and potato using both Agrobacterium and Transbacter-mediated (Rhizobium leguminosarum bv. 'Trifoli ANU845' containing the vector pCAMBIA5106) transformation systems. Two systems were used to investigate the effect on gene transfer (determined using a GUS assay). Firstly, a pre-inoculation step with different PGPRs (commercially available Bacillus and Pseudomonas isolates) followed by transformation with either Agrobacterium or Rhizobium. Up to a 5-fold increase in transformation rates were recorded. The second system examined the influence of volatile organic compounds (VOCs) emitted by these PGPRs on potato explants prior to gene transfer with >7-fold increase with Rhizobium and >l5-fold increase with Agrobacterium-mediated transformation recorded. This preliminary study offers an exciting insight into how to vastly improve the rate of transformation particularly when using the Transbacter technology, an important technology in the field of genetic engineering, and one which is not curtailed by patenting law.