Beating drought with the help of resurrection plants

If molecular biologist Prof Jill Farrant is successful, farmers could soon have access to cultivars that can withstand one
or even two months of extreme drought.

Beating drought with the help of resurrection plants

By as early as 2050, climate change is likely to have affected agriculture in Africa so badly that, in some areas, crop farming will be abandoned as the continent experiences greater and greater periods of drought. According to Jill Farrant, professor of molecular and cell biology at the University of Cape Town, plant water-deficit stress is one of the greatest threats to world agriculture and, in the coming decades, is likely to be exacerbated by the effects of climate change.

However, a considerable increase in yield can be achieved by growing drought-tolerant crops and pasture grasses.
According to Farrant, planting such crops will extend the length of the growing season and expand the area where such crops can be grown, thereby accommodating the fluctuations in climatic conditions. With this in mind, she has spent the past decade researching ‘resurrection plants’, with the aim of developing crops that will be both resistant to and highly tolerant of drought.

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A leading authority on the subject, Farrant explains that resurrection plants ‘come back to life’ from a desiccated, seemingly dead state when they are rehydrated. Her research involves a systems biology approach to understand the protection mechanisms laid down in orthodox seeds and vegetative tissue of resurrection plants, with the ultimate aim of using key protectants identified to make drought-tolerant crops. She was recently honoured as the 2012 laureate of the L’Oréal-Unesco Award in Life Sciences for the Middle East and Africa for her work on resurrection crops and desiccation tolerance.

All plants have the genes
All living organisms on the planet consist predominantly of water. In animals, the loss of more than 1% to 10% of water – depending on the species – can be dangerous, while plants can lose 10% to 40% of their water content before they die, explains Farrant. 

“What makes resurrection plants so special is that they can lose up to 95% of their water and still survive for years to regenerate fully, within 24 to 48 hours, when rehydrated. Desiccation tolerance is the ability of a plant or plant part to come into equilibrium with atmospheric relative humidity and to survive in this state for ecologically significant periods.

Prof Jill Farrant. Photo courtesy of UNESCO For Women In Science

“All plants have the genes that enable desiccation tolerance, but most use them only for seed. Resurrection plants can also switch these genes on in their leaves and roots whenever drought occurs.” The mechanisms of desiccation tolerance in lower order resurrection plants (lichens, algae and mosses) differ from those in angiosperms, such as crops.

“In angiosperms,” says Farrant, “tolerance is achieved largely by stimulating protection mechanisms during dehydration. If we can understand the mechanisms whereby vegetative tissues tolerate extreme water deficit, we can use this knowledge to develop drought-tolerant crops.”

Targeting photosynthesis
It stands to reason that food crops that can survive long stretches without water will become more important as climate change worsens. “If we can understand how resurrection plants tolerate water loss, we can start developing a plant that is already drought-resistant into a drought-tolerant crop,” continues Farrant. Her research has examined the mechanisms that these plants use to survive water loss and prolonged drought.

“I’ve looked at what genes they need to switch on, what protein and lipid changes occur and what metabolites they produce. I’ve also studied what signals they send out,” she says. “In short, we’ve looked at all the key protectants that enable desiccation tolerance in these plants.” After identifying these, Farrant targeted photosynthesis in her applied research.

“Our discoveries showed that if we can protect photosynthesis – in other words, keep it going in a plant suffering severe water stress – we can develop a plant that will be able to keep going for much longer than the drought-resistant crops that are currently available,” she explains.

GM – Key to the future
Farrant believes strongly that using genetic modification (GM) to breed crops will help feed a rapidly growing population in an era of extreme climate unpredictability. “I’m certain that much of the negativity surrounding genetic engineering
has more to do with ignorance than with anything else,” she says. “It can take 50 years to breed drought tolerance in crops through selection – or biotechnology can be used to breed the same crop in three years.”

Using GM in developing drought-tolerant crops does not mean that she is inserting any ‘strange’ or ‘foreign’ genes into the crops, however. “I’m not creating Franken-food,” she insists. “We’re applying genetic modification to regulate genes that are already present in these plants. “As I explained, my research has proved that a large proportion of the protection mechanisms in resurrection plants are already present in the seeds of most plants.

These genes are not switched on in the vegetative tissue of such plants, but in resurrection plants they’re switched on in leaves and roots. “Through genetic modification, we’re trying to regulate – and find a way to activate – those genes in the vegetative tissue of crops in times of severe drought.”

Surviving up to two months
Farrant is currently conducting tests on maize, sugarcane and Eragrostistef, a grass cultivated in Ethiopia, where its
high-protein, gluten-free seeds constitute a food staple. “I’m not turning maize or any of the other plants under research into resurrection plants,” she says. “They will not be able to tolerate such extreme desiccation as losing 95% of their water. But they will be able to tolerate drought for much longer periods than any of the drought-resistant crops currently available. “My aim is to get these plants to a point where they can survive one or even two months without water, instead of two weeks, as is currently the case.”

Overcoming Funding problems
The only factor that is currently putting a brake on Farrant’s progress is a lack of funding. “As an academic, I have to source all my own funding and it has been an uphill battle,” she explains. “But I hope that the exposure of the L’Oréal-Unesco Award, which includes prize money for my research, will bring in more support.” Provided she can secure sufficient funding, Farrant expects to start field trials of extreme drought-tolerant crops within five to 10 years.

Contact Prof Jill Farrant at [email protected]