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Undersupported, but undaunted

Nature Biotechnology volume 25, pages 1219–1220 (2007)Cite this article

But on the surface, things are going well. Recent work from his laboratory and elsewhere has demonstrated that human proteins like insulin and interferon can be made in plants with engineered chloroplasts at levels not possible with nuclear trangenes. In a later Nature Biotechnology paper2, he reported that 45% of tobacco leaf protein was derived from a transgene, the insecticidal protein cry2Aa2, representing the highest level of foreign gene expression ever reported in plants at the time. Since then, equally impressive levels of insulin and interferon have been achieved using the system3,4. Low expression levels is the thing that Daniell feels has held back the field of plant-made pharmaceuticals—or at least one of the things. And with his chloroplast vector, which inserts into all 10,000 copies of the chloroplast genome, he feels he has that problem solved.

Another virtue of targeting the chloroplast genome with a transgene is that containment is not an issue. Because the chloroplast genome is maternally inherited, pollen won't disseminate the transgene. And with tobacco, one of the Daniell systems, at the time of harvest, there are no flowers (they harvest leaves), so no reproductive organs are involved, which should make regulators breathe a sigh of relief. In fact, four transgenic plants have been approved for field trials, and the results of one such trial (insulin) have recently been reported5.

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References

  1. Daniell, H. et al. Containment of herbicide resistance through genetic engineering of the chloroplast genome. Nat. Biotechnol. 16, 345–348 (1998). (154 citations)

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  2. De Cosa, B. et al. Overexpression of the Bt cry2Aa2 operon in chloroplasts leads to formation of insecticidal crystals. Nat. Biotechnol. 19, 71–74 (2001). (125 citations)

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Undersupported, but undaunted. Nat Biotechnol 25, 1219–1220 (2007). https://doi.org/10.1038/nbt1107-1219b

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