Making plants work harder [or, Vorsprung durch Botanik]

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Image: Luigi Chiesa/Wikimedia Commons.
Image: Luigi Chiesa/Wikimedia Commons.

Not content with just being grateful for all of the marvellous things that plants do and provide, we humans always seem to want them to do even more. Well, in that vein there has been a veritable avalanche of stories that exploit the impressive chemical synthetic abilities of plants. Moran Farhi et al. have managed to persuade tobacco to manufacture artemisinin. Why? Artemisinin – and its derivatives – are a group of drugs that possess the most rapid action of all current drugs against Plasmodium falciparum malaria, a mosquito-borne infectious disease estimated to kill 2.23% of the world’s population according to the World Health Organization’s (WHO) 2011 World Malaria Report. Yes, but why in tobacco? Although artemisinin is isolated from its namesake Artemisia annua, low-cost artemisinin-based drugs are lacking because of the high cost of obtaining natural or even chemically synthesized artemisinin. Elsewhere, Xing Xu and colleagues have created recombinant human collagen in transgenic maize. But not only that, they importantly demonstrate that such a ‘system’ has the ‘potential to produce adequately modified exogenous proteins with mammalian-like post-translational modifications that may be required for their use as pharmaceutical and industrial products’. And, exploiting another major crop for human protein ends, Yang He et al. have designed rice to make human serum albumin (HAS), at levels >10% of the total soluble protein of the rice grain. Proper human-derived HSA is in short supply because of limited availability of donated blood, but is widely used in production of drugs and vaccines, and in treatment for severe burns, liver cirrhosis, and haemorrhagic shock. As the authors conclude, ‘Our results suggest that a rice seed bioreactor produces cost-effective recombinant HSA that is safe and can help to satisfy an increasing worldwide demand for human serum albumin’. Finally, news that an anti-HIV (Human Immunodeficiency Virus, which causes AIDS, Acquired ImmunoDeficiency Syndrome) antibody produced in GM tobacco underwent clinical trials in the UK in 2011. Testing was intended to establish how safely and effectively the vaginally applied product stops HIV transmission and was carried out under the watchful eyes of the UK’s Medicines and Healthcare products Agency (MHRA) at the University of Surrey Clinical Research Centre. Apparently the UK was chosen for the honour of this pharmaceutical ‘first’ because the Pharma-Plant Consortium – which is leading the trial – were put off by the level of fees required by the EMA (European Medicine Agency). So, UK vs. The Rest of Europe (c’est la vie, again…). Supporters of this whole approach to human exploitation of plants – so-called molecular farming – argue that: protein drugs could be made more efficiently and cheaply inside GM crops, since plants are extremely cost-effective protein producers; mass producing medicines in GM plants uses lower-cost tech than those of biopharmaceuticals made in huge stainless steel fermentation vats containing bacteria or mammalian cells; production costs could be 10 to 100 times lower than using conventional bioreactors; and the relatively simple manufacturing process could be transferred to developing countries. Now, surely, those fantastic plant pharma feats have got to be more impressive than getting a silkworm to spin spider silk, as reported by Florence Teulé et al.! But, if I’ve (unintentionally!) awakened in you a desire to discover more arachnoid antics, try Martin Humenik and colleague’s review of recombinant spider silks.


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