Wednesday, November 10, 2010

Meganucleases, the End of GMO plants?


By Daniela Sciaky, Ph.D.

Advancements in DNA sequencing technology have produced a large library of completed plant genome sequences. These sequences are an important step to the introduction of desirable characteristics into plants such as soybean and corn, including those traits important to the production of biofuels. Coupled with these sequences are advancements in the technology to breed plants for these traits.

Cellectis plant sciences, a subsidiary of Cellectis (Alternext: ALCLS) designs meganucleases that can be used to make targeted gene modifications. Recently the company announced the licensing of PureIntro® Agrobacterium transformation technology for monocotyledonous plants such as corn and rice from Japan Tobacco Inc. and Aerosol Beam Injector technology from Midwest Oilseeds Inc. These tools will be used by Cellectis plant sciences to modify plant cells by helping to deliver meganucleases into plant cells. Likewise, Precision BioSciences has also developed meganuclease technology for plant genome modification.

Meganucleases are enzymes that recognize specific strings of DNA sequence containing more than 12 nucleotides. These specific sequences occur in the plant genome rarely, no more than two times. Cellectis plant sciences, as well as Precision BioSciences, design meganucleases that can make targeted gene modifications without deleteriously affecting other genes. The plant’s DNA replication apparatus is used in conjunction with the meganucleases to introduce modification of specific genes.

The advantages of this technique are enormous and have implications for the development of GMO crops. Because endogenous genes are targeted for modification, no foreign sequences are retained or can be removed after the modification has taken place. Expression of the modified gene is not affected by any random placement in the genome as might occur with other modification systems. The time to achieve regulatory approval of the modified plant can potentially be reduced.

Many of the commercial plant sciences companies have become interested in the technology. Precision BioSciences is collaborating with DuPont, Bayer CropSciences and BASF Plant Sciences while BASF, Bayer CropSciences, Pioneer, Limagrain and Monsanto are reported to use Cellectis plant sciences technology. However these two technology companies appear to be embroiled in a series of patent disputes. On October 28th Precision BioSciences announced that the US Patent and Trademark Office (PTO) had issued final decisions rejecting the claims of four Cellectis patents. Whatever the outcome, expect to see more companies interested in this technology.

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