Hacking plant ‘blood vessels’ could avert food crisis
Today’s wars are not about food, but not too far in the future they could be. The number of people dying of starvation has been falling for decades, but the decline in the numbers of hungry people is slowing down. More than 800 million people remain undernourished. With nine billion mouths to feed by 2050, the task of feeding us all is only going to get harder.
There is a solution, though, according to a recent paper in the journal Nature written by some of the world’s leading plant biologists. They show that, by hacking how plants transport key nutrients into plant cells, we could solve the impending food crisis.
Each plant is made of billions of cells. All these cells are surrounded by membranes. The pores in these membranes are lined with special chemicals called membrane transporters. They do the job of ferrying nutrients that plants capture from soils with the help of roots.
What scientists have learnt is that if such membrane transporters are tweaked, they can enhance plant productivity. When these tweaks are applied to crops, they can produce plants that are high in calories, rich in certain nutrients or fight pests better. All these methods increase food production while using fewer resources.
Currently, world agriculture faces the problem of shrinking arable land, which is the area that is fit for food production. This is why the world’s leading plant biologists argue in the Nature paper that we must embrace genetically modified (GM) plants, many of which have better membrane transporters making them more productive without increasing land use.
Over two billion people suffer from iron or zinc deficiency in their diets. Biofortification involves increasing concentration of such essential minerals. Simple genetic modification increases the amount of membrane transporters that ferry these minerals. Such plants when ready for harvest can have as much as four times the concentration of iron, compared to that of common crop variety.
A little known fact (pdf) is that making fertilisers consumes about 2% of world’s energy. This makes the process a significant contributor to emission of greenhouse gases. Modifying membrane transporters can help cut those emissions, because it can make a plant more effective at using plant fertilisers.
For instance, only 20-30% of phosphorus added to soil as fertilisers is used by crop plants. Tweaking transporters such as PHT1 can increase the uptake of phosphorus. Similar results can be obtained when NRT genes are modified, which increase uptake of nitrogen from fertilisers.
About a third of the Earth’s ice-free land is acidic. The problem is that in highly acidic conditions aluminium in soil exists in a form that is toxic to plants. Such land cannot be used to grow food, but if crops were able to counteract the effects of acidity on growth that land would become available.
Scientists have found some varieties of wheat that have a trick to enable them to grow in acidic conditions. One of its membrane transporter called ALMT1 pumps out malate anion from its roots into the soil which traps the toxic form of aluminium.
Varieties of wheat without this natural transporter can be improved by breeding with varieties that do. But, crops such as barley, which have no comparable system of transporter in its membrane, need to be genetically modified to express the ALMT1 transporter protein. This allows for greatly increased yields even in acidic soils.
When salt is bad
Much of the world’s arable lands are becoming salty as a result of current irrigation practices. This happens when, on evaporation, salts in irrigation water are left behind inthe soil. Salts are toxic to plants and are severely limiting yields in over 30% of irrigated crops.
But there are membrane transporters which can stem the flow of salts into plants. These transporters, from the HKT family, rid the water of sodium before it is taken up by the plants. One example is that of durham wheat, which was modified to possess the HKT5 gene. The modification helped increase its yield in salty soils by 25%.
Fighting from the inside
Disease-causing micro-organisms, pathogens, manipulate a plant’s functioning and consume the fruit of its labour. Most crops have membrane transporters called SWEETs that move sucrose made by leaves from photosynthesis to other regions where it may be stored. Plant pathogens have evolved to manipulate SWEET genes so that sugars are moved to cells where they can feed on the goods.
Now scientists have found a way of disrupting this pathogen-induced manipulation by a method called RNA-silencing. These reduce, or sometimes eliminate, the pathogens’ ability to feed on the plants’ hard work, and in turn they help increase plant productivity.
Not all bad
Researchers have been quietly chugging away in labs working on making such radical improvements to crops. Breeding of plants, a form of untailored genetic modification that bestowed most of the benefits to agriculture a generation ago, is not able to keep up with the pace of change required for an ever-increasing demand for food. That is why it is important that we understand the science behind the process of tinkering with specific genes, before jumping on the “GM is bad” wagon.
Scientists are aware of the moral, ethical and environmental discussions surrounding production of GM food, and have been working carefully to address those issues. It is important that they continue to do so, while exploring the full potential of GM research to tackle the issue of hunger that looms large over the future of our species.