Genetic modification (GM) has been a hot topic for the past couple of decades, and with scaremongering over ‘Frankenstein foods’ you’d be forgiven for thinking that GM is only being used to produce horrifying steroid-addled mutant plants, which will one day develop a taste for human flesh and take over the Earth (like in Day of the Triffids or those annoying carnivorous flowers in Super Mario).

But imagine for a second that scientists are not trying to hasten the end of humanity, but instead to prolong it. What sort of modifications might actually prove useful in trying to provide food for malnourished populations?

A new study by scientists from China and Germany has looked at several ways of improving the drought-resistance of a species of cress plant (Arabidopsis thaliana), by tweaking a number of common plant genes, including some first associated with surviving extreme cold.

So, what’s the point?

Plants are not just static, passive items of scenery – they are living organisms which compete and battle to survive in the same way as animals. So they can respond to external stresses, such as lack of water, and adjust their own biochemical processes to help them survive.

C-repeat/dehydration–responsive element binding factors (mercifully abbreviated to CBFs) are proteins which control how often particular genes are expressed and are commonly found across the plant kingdom.

CBFs are produced by plants in response to external stresses such as dehydration and cold and alter the plant’s internal mechanisms by either activating or suppressing particular genes.

Another way that plants can be modified is through a particular gene called ESKIMO1 (or ESK1). While the name might be unfortunate (‘eskimo’ is considered a pejorative term in some places), a mutated form of the gene can actually prove quite useful in plants trying to conserve water.

The mutation is believed to be a defect in the plant’s water transport system (lower transpiration rate), but while this would mean growth would be hindered under normal conditions, it means water is used more efficiently and can therefore be advantageous if liquid water is scarce (such as in cold or drought conditions).

The scientists wanted to see if controlling both CBFs and ESK1 could improve the survival of Arabidopsis plants in simulated drought conditions.

What did they do?

The researchers used genetic techniques to boost production of CBFs and to suppress ESK1.

To boost the CBFs they spliced in a ‘promoter’ sequence ahead of the CBF code in the plant genome. This means that the proteins coded by the CBF genes will be produced more often and CBF levels will increase.

ESK1 was suppressed by using small-interfering RNAs (siRNAs). These molecules interrupt the process of turning genetic information in the DNA into functioning proteins (specifically binds to mRNA to reduce translation of gene into protein).

The researchers compared how normal (wild-type) plants and their transgenics grew in both normal medium and simulated drought conditions (water contained 30% poly(ethylene glycol) which modifies the osmotic potential).

They then took the most successful transgenic plants and compared them to the wild-type in a greenhouse for five weeks. All of the plants were fully watered for 2 weeks after germination form seeds, not watered for the following two weeks then fully watered again for the final week.

Did they prove anything?

After 14 days of growth, there were no noticeable external differences between wild-type and any of the transgenics and ESK1 suppressed under normal conditions, but under simulated drought several transgenics had ‘better root systems’ and more leaves than the wild type.

Of the transgenics tested in the greenhouse, all of them outperformed the wild-type. ESK1 suppression was found to be more effective than CBF promotion, but a mutant which both suppressed ESK1 and overexpressed a CBF inducer protein had the highest survival rate of all.

But drought tolerance comes at a price – under normal conditions, the most successful transgenics had lower seed production around half of that of the wild type.

So, what does it mean?

The researchers showed that their transgenic plants were much better at surviving in drought conditions than the wild-type. But under normal conditions, these plants produce far fewer seeds – a major problem because for many staple crops such as wheat and rice, this is the part of the plant that we actually eat.



So unless this issue can be addressed, this method of introducing drought-resistance will not be viable in regions where drought happens infrequently. There seems little point in using a plant that can produce more than the wild-type in a one-off drought year, but much less in the majority of years where rainfall is normal.

However, it might be useful in regions where drought is more common, particularly at the fringes of deserts, or to dispense to farmers if a drought is considered highly likely.

GM crops may have a bad reputation – arguably due to negative media coverage, but the more we can understand about the genetics of plants and their effects on how the plants grow, the easier it will be for us to tune them into useful tools to fight against malnutrition and starvation.

Original article in PLOS One Sep 2014



All images are open-source/Creative Commons licence.

Credit: Peripitus (First); PublicDomainPictures (Second); A Salguero Quiles (Third); Xu et al. (Fourth); USDOA (Fifth)



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Find more articles like this in:

Xu F, Liu Z, Xie H, Zhu J, Zhang J, Kraus J, Blaschnig T, Nehls R, & Wang H (2014). Increased Drought Tolerance through the Suppression of ESKMO1 Gene and Overexpression of CBF-Related Genes in Arabidopsis. PloS one, 9 (9) PMID: 25184213