Nature 433, 629 - 633 (10 February 2005); doi:10.1038/nature03309

SUMMARY
By Mona Akbari

Breakthrough removes obstacles in biotechnology

Researchers at CAMBIA have made a breakthrough in biotechnology by successfully transferring genes to plants using several bacteria other than Agrobacterium tumefaciens or At, that so far has been considered the only microbe capable of such gene transfer. The discovery has earned the scientists a publication in Nature, one of science’s most prestigious journals.

The finding is particularly significant since using At for gene transfer to plants is covered by complex patenting laws that has prevented its use by many organizations worldwide. The new technology is an exciting alternative, since it will be available through an ‘open-source’ license that has no commercial restrictions, but requires a commitment to sharing improvements.

Agrobacterium is commonly found in soil and naturally parasitizes plants by inserting its bacterial genes into the plant’s genome. The inserted segment, referred to as T-DNA, is present in At as part of a larger circular DNA fragment known as the Ti plasmid. Until now it has not been conclusively shown that the Ti plasmid can be used in other bacteria for gene transfer to plants.

The team at CAMBIA introduced a specially modified Ti plasmid into three different types of bacteria, Rhizobium, Sinorhizobium and Mesorhizobium, that are closely related to At, to test whether these bacteria would allow gene transfer to plants. Another fragment of DNA or vector was also introduced into the bacteria. It contained several components including the transferring T-DNA, as well as a gene for GUSPlus™ that allows a colour test in plant material to ensure that gene transfer has occurred.

The altered bacteria were grown on leaf pieces of tobacco and tested for gene transfer by the use of the GUSPlus activity colour test, which clearly showed the characteristics associated with successful gene transfer. As expected, GUSPlus activity was not observed in control experiments where the bacteria contained the vector but not the Ti plasmid. Once the tobacco plants were regenerated from the leaf discs, further tests also confirmed that the T-DNA had integrated into sites within the plant genome.

Sinorhizobium was also able to mediate gene transfer in other plants such as rice and the model plant Arabidopsis thaliana, while Rhizobium allowed gene transfer to Arabidopsis. All regenerated plants from these experiments were conclusively shown to have T-DNA integrated into their genomes.

It is extremely useful that Sinorhizobium is able transfer genes to a range of plant tissues in both broad-leafed dicotyledonous and narrow-leafed monocotyledonous plants. Many important crops have been resistant to gene transfer by At and this new technology may provide the answer.

CAMBIA has applied for a patent on this technology and offers TransBacter™, the collective name it has given these bacteria, as an ‘open-source’ alternative to the international community. This will be achieved through an innovative license concept, called BIOS – Biological Innovation for Open Society – which is based on precedents in computer software, but has been adapted for patented technology to ensure sharing of improvements.

NATURE summary

Open-source gene transfer

Control of the biotechnology involved in producing genetically modified crops is concentrated in the hands of a few multinational companies, in part because of the complex web of patents involved. A group at CAMBIA, the Center for the Application of Molecular Biology for International Agriculture in Australia, set out to untangle this web and make the technology more widely available by developing a work-around for a key enabling technology in plant biotechnology, Agrobacterium-mediated transformation. They found that other species of benign bacteria can be modified in a surprisingly simple way to do the same job, and the resulting gene transfer technology is to be made available on an 'open source' basis as part of the recently launched BIOS initiative (Nature 431, 494; 2004).

Read the Nature paper

Read the accompanying News and View paper by Stanton B. Gelvin