Feed the world – turning cotton into a food crop

The world’s cottonseed harvest have enough protein to feed half a billion people in the world’s poorest places, but are inedible because they contain a potent poison. Now, scientists have found a way of removing that poison, and turning cotton into a stunning new food source.

 

Feed the world. Let them know it’s Christmas time.” The world is currently home to 6.5 billion people and over the next 50 years, this number is set to grow by 50%. With this massive planetary overcrowding, Band Aid’s plea to feed the world seems increasingly unlikely.

Current food crops seem unequal to the task, but scientists at Texas University may have developed a solution, a secret ace up our sleeves – cotton.

Cotton is infused with a potent poison called gossypol. Cotton is famed for its use in clothes-making and has been grown for this purpose for over seven millennia. We do not think of it as a potential source of food, and for good reason.

The seeds of the cotton plant are rife with a potent poison called gossypol (see below) that attacks both the heart and liver. Only the multi-chambered stomachs of cattle and other hooved animals can cope with this poison, relegating cottonseed to a role as animal feed.

Getting rid of gossypol could go a long way to reducing the world’s hunger crisis. A fifth of a cottonseed’s weight is made up of oil, and a quarter of high-quality protein. For every kilogram of fibre, each cotton plant produces 1.65 kg of seed.

And the plant is grown in over 80 countries by some 20 million farmers, the majority of whom live in the poorest parts of the world, where starvation is an ever-looming threat. If only the seeds could be made edible.

GossypolIn 1954, scientists attempted to launched a programme to cross-breed normal cotton plants with a mutant strain that lacked the glands that make gossypol. Unfortunately, they discovered that cotton creates the poison for a reason.

It infuses the plant’s various tissues, protecting it from insect pests and infections alike. The programme’s seeds were safe for human consumption, but the weakened plants readily succumbed to insect attacks, destroying their commercial potential.

Now, Ganesan Sunilkumar and colleagues have solved the problem. They have used a technique called RNA interference, or RNAi, to turn off a gene called delta-cadinene synthase, which is essential for gossypol production.

But in this case, the team put their system under the control of a genetic switch used only in cotton seeds, and not the rest of the plant. As a result, levels of gossypol plummeted in the plant’s seeds and these alone. The rest remained as strong as ever against attackers.

Sunilkumar ran their special plants through a series of tests to make sure that the RNAi’s effects never spread to the rest of the plant. They passed every one. Best of all, the altered plants stably passed on their characteristics to their daughters.

This study is testament to both the power and the precision of modern genetic technology. The researchers identified a very specific point in a biochemical pathway and blocked it in a single part of the plant. The result is a variant that retains the original’s survival abilities, but is suddenly fit for human consumption.

Their approach has tremendous potential for opening up other food sources. For example, the beans of the tropical grass pea, Lathyrus sativus, are often eating by poor people in Africa and Asia in times of dire need.

As the beans contain a potent neurotoxin – a nerve poison – those eating them often contract a neurological disease called lathyrism. With Sunilkumar’s technique, lathyrism could become a thing of the past.

For those who feel that the use of such technology is tantamount to playing God, consider this. Every year, 44 million tons of cottonseed are wasted. With this new technology, the engineered seed could provide enough protein for half a billion people every year.

Sunilkumar, Campbell, Puckhaber, Stipanovic & Rathore. 2006. PNAS 103: 18054-18059.

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2 Responses

  1. I am glad someone has found a way to get around the poison and think this should be used for food in our future and Praise God for the founding of it.

  2. This is a very impressive technical achievement and is very encouraging. However, we must be cautious when introducing new technology not to create new problems and earn a public backlash against it. This technology relies on the expression of an RNA-based inhibitor to remove most (99%!) of the gossypol from the cottonseed. The resulting seeds are thus safer than those from which the glands are now removed by mechanical means for oil production. But the plant has no “motivation” to keep producing the inhibitor, which is essentially a new, artificial gene, and for various known and unknown reasons may tend to get rid of it in future generations more quickly than might be expected from chance. Another factor is that the natural gene for the poison can mutate over time, especially if this provides some resistance to insects, and even small differences between the gene and the RNAi are sufficient to reduce its effectiveness. As the expression of the inhibitor wanes, the crop could gradually become more toxic. Another factor is of course the possibility of genetic contamination from natural cotton pollen.

    Now, this might not be a problem if gossypol levels are always tested and good seed is always available for replanting. But for a “starvation crop” there may not really be any testing, and the first we may hear about the problem is when several villages start complaining that they can’t have any children – did I mention that male fertility is one of the first things affected by gossypol, which was actually tested as a male contraceptive until the researchers decided it was not so reversible as hoped? While it is possible that the inventor, who holds US Patent US 2004/133944 on the technology, might graciously permit poor people to have unrestricted access to safe seed stocks, there is certainly no legal requirement for him to do so – in which case this crop could end up as a particularly disturbing case of “Terminator Technology” restricting the replanting of seeds through the threat of sterility or worse.

    In short, I think that this is a useful lead, but I don’t think it’s a good idea to put plants out into circulation that are food until, in some number of generations, they turn into poison. There might be a way to overcome this problem, but it will be a tough sell as far as I’m concerned.

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