Natural GMOs Part 80. Bacteria mate with fungi on plant surfaces.

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It has long been known to the common bacterium called Agrobacterium can inject DNA into plant cells. It naturally causes shape alterations called galls on plants that are infected with this bacterium as a result of its ability to inject genes it carries inside its own cells into plant cells. Ability to mate with other organisms is well established and widely studied among common bacteria such as E. coli, and they can be very promiscuous, in that a wide range of target organisms including very unrelated organisms such as yeasts can accept genes from them in the mating process. But to do an injection of DNA into a target organism Agrobacterium needs to be stimulated by chemical signals from plant material.

This scientific paper shows that chemical signals on plant tissues are available to encourage mating by these same Agrobacterium bacteria with fungi that grow on plant surfaces. The work documents that genes can naturally pass between bacteria and fungi  on the surfaces of plants.  It’s one of the many demonstrations that natural gene movement occurs between widely separated organisms on evolutionary trees, as fungi and bacteria, which are very distant relatives on the evolutionary tree of life.

 Investigating Agrobacterium-Mediated Transformation of Verticillium albo-atrum on Plant Surfaces
Agrobacterium tumefaciens has long been known to transform plant tissue in nature as part of its infection process. This natural mechanism has been utilised over the last few decades in laboratories world wide to genetically manipulate many species of plants. More recently this technology has been successfully applied to non-plant organisms in the laboratory, including fungi, where the plant wound hormone acetosyringone, an inducer of transformation, is supplied exogenously. In the natural environment it is possible that Agrobacterium and fungi may encounter each other at plant wound sites, where acetosyringone would be present, raising the possibility of natural gene transfer from bacterium to fungus.

Methodology/Principal Findings
We investigate this hypothesis through the development of experiments designed to replicate such a situation at a plant wound site. A. tumefaciens harbouring the plasmid pCAMDsRed was co-cultivated with the common plant pathogenic fungus Verticillium albo-atrum on a range of wounded plant tissues. Fungal transformants were obtained from co-cultivation on a range of plant tissue types, demonstrating that plant tissue provides sufficient vir gene inducers to allow A. tumefaciens to transform fungi in planta.

This work raises interesting questions about whether A. tumefaciens may be able to transform organisms other than plants in nature, or indeed should be considered during GM risk assessments, with further investigations required to determine whether this phenomenon has already occurred in nature.

Citation: Knight CJ, Bailey AM, Foster GD (2010) Investigating Agrobacterium-Mediated Transformation of Verticillium albo-atrum on Plant Surfaces. PLoS ONE 5(10): e13684. doi:10.1371/journal.pone.0013684

Received: June 14, 2010; Accepted: October 5, 2010; Published: October 27, 2010

Copyright: © 2010 Knight et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

 See also
Natural GMOs Part 10. Genes move around in nature from bacteria to fungi

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David Tribe is an applied geneticist, teaching graduate/undergrad courses in food science, food safety, biotechnology and microbiology at the University of Melbourne.