Resurrection plants: The drought-resistant 'zombie plants' that come back from the dead

To protect crops from rising droughts, scientists are looking to the genes of a small group of plants that can survive months of drought then regreen within hours.

It was as a child growing up in South Africa in the 1970s that Jill Farrant first noticed several plants around her apparently coming back from the dead.

These plants, she later learned, can survive six months or more without water. Their leaves turn brown and brittle to the touch but, given water, they will regreen within hours. Within a day, they've returned to their former self and can continue to photosynthesise.

While such a Lazarus-like ability is common among mosses, ferns and other non-flowering plants, these "resurrection plants" belonged to the angiosperms, or flowering plants, the group that includes every blossoming tree and fruit-bearing, seed-carrying crop. But out of the 352,000 known species of flowering plants only 240 are resurrection plants. Scattered across this branch of the tree of life, they are often unrelated, each having independently evolved the ability to live without water. Primarily found growing on the rocky slopes or gravelly soils of South Africa, Australia and South America, the tactics used for this zombie-like trick are surprisingly similar – almost as if an ancestral toolkit can be retrieved from deep inside their DNA to deal with the problem of drought.

Farrant, now a professor of desiccation tolerance at the University of Cape Town, has been studying these unusual plants for over three decades. Along with several other researchers, she believes the drought-resistant powers found in their genes may be key to adapting agriculture to a future of climate change.

For plants to survive for months without water may seem like science-fiction. The vast majority of plants do indeed die when they experience water loss of 10-30%. But resurrection plants are able to tolerate over 95% water loss.

But it's not just the ability to survive drought that is important for these species, says Carlos Messina, a maize scientist at the University of Florida. It's also how resurrection plants regrow following drought.

Maize plants might also survive after a drought, he says, "but when they rehydrate, they don't go back to the same leaf architecture they had before, and the flow of CO2 and water is all messed up". Drought therefore compromises their growth long after the rains have returned.

But resurrection plants "seem to come back to the form that they had before the drought," he says. "If we can create maize that does that, that's fantastic, because we can regain that productivity."

Resurrection plants have evolved this essential skill by replacing disappearing water with sugars such as sucrose, turning the inside of their cells into a viscous, glass-like substance that slows down any chemical reactions. Known as vitrification, the same tactic is used by desiccation-tolerant animals such as tardigrades (also known as water bears) and the eggs of Artemia shrimp (sea monkeys).

As they turn to glass, these plants also deconstruct their photosynthetic machinery (such as chloroplasts), switching off their primary source of food as they turn to a state of dormancy. To hold their assembly of proteins and cell membranes together, they secrete a suite of protective proteins known as "chaperones", since they guide the cell through dangerous times. 

"How they preserve their tissue is quite a miracle," Farrant says.

In a sense, the abilities of resurrection plants are not so different to the seeds of most flowering plants. When dried and stored in a dark and cold place, many seeds can survive for years, sometimes millennia, preserving the recipe to make a new plant when warmth and water return.

But once the first green shoot emerges, this "desiccation tolerance" is lost, traded for faster growth, high yield and more nutritious fruit or seeds. It's a trait that the green revolution, the 20th Century agriculture boom which introduced high-yielding varieties of crops grown in optimum conditions of water, soil and Sun, exacerbated.

Meanwhile, while droughts have always been an issue for farmers, rising global temperatures due to ongoing greenhouse gas emissions are making them far worse, especially in the Mediterranean and western North America. Drought, wildfires and heat are estimated to have cost $16.6bn (£12.9m) in crop losses in the US alone in 2023. According to some climate models, by 2100 much of the agricultural land in sub-Saharan Africa and South America will be unsuitable for food production, a large proportion made barren by drought.

"Agriculture will only be possible in Canada and Siberia," says Henk Hilhorst, a retired seed scientist based in the Netherlands. It is these northerly regions of the planet, not the tropics, that will have to feed the world.

The situation is so severe, argues Farrant, that even the most radical shifts in agriculture now have to be considered. "We're just not going to get enough food," she says. "So we've got to become incredibly inventive."

The most common crop plants such as wheat, maize and soybean have already been made more resilient to water scarcity through selective breeding. Choosing plants with greater root depth helps them find deeper reserves of water, for example, or choosing those that flower faster helps produce seeds in a shorter growing season.

But extreme weather events aren't just becoming more common, they are becoming more unpredictable. Chaos is the marker of climate change, says Timothy George, a soil scientist at the James Hutton Institute in Scotland. "There's just much more variability." Periods without water occurring out of the blue – known as flash droughts – are becoming more common, as are droughts that occur during months of the year once guaranteed rain and mild conditions. 

This means that avoiding drought may stop being possible. That's why Farrant and other scientists are investigating whether they can find a way to recreate the remarkable desiccation tolerance of resurrection plants in ordinary food crops.

To introduce such talents to rice, maize and wheat was long thought to require the use of "transgenic" genetic modification – introducing DNA into their genome from distant relatives in the plant kingdom. The genes involved in desiccation tolerance would be isolated and inserted into drought-sensitive crops, a task that has been made simpler with the recent rise of Crispr gene editing technologies.

But Farrant's recent studies suggest that many of the genes used to survive desiccation are the same as those found in seeds of most flowering plants. To create drought-resistant crops, therefore, might not require any new genes at all; by activating the same genetic toolkit found in their seeds, a mature plant might be made more resilient to drying out. As this would involve activating genes that have simply been silenced upon germination, rather than inserting foreign genes from other plants, it may not be as controversial as some other genetically-modified crops.

Julia Buitink, a seed biologist at the French National Institute for Agricultural Research in Paris, agrees it's a feasible approach, even if the effect were limited to the young seedlings of the crop. Seedlings could be an easier target, she says, primarily because this stage of growth follows germination, and extending desiccation tolerance would be the most logical first step. Plus, because most desiccation-tolerant organisms are small, these seedlings would fit the mould already found in nature. 

Still, while these techniques are feasible in any laboratory in the world, there remain huge gaps in our knowledge when it comes to how these plants survive desiccation, especially when it comes to howeach adaptation is controlled. "I think we know the main genes," says Buitink. "The problem is the higher level – how can we switch them on when there is drought? And for that we really don't know much about it."

The genetic switches that have been identified, Buitink adds, are often not specific to one thing: turn on desiccation tolerance, she says, and you will almost certainly change many other parts of the plant – and most importantly, may decrease its yield. "Which, for crops, is exactly what you don't want."

But if a "master switch" – a gene specific to inducing desiccation tolerance – can be found, it could be turned on only when water scarcity becomes an issue, ensuring that the yield of these crops would be unaffected if conditions are conducive to growth. Just as a resurrection plant only shrivels into a crinkle of brown leaves during the long dry season, a crop plant might only batten down the hatches when a flash drought comes out of the blue.

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This is exactly what researchers in Kenya and Sweden achieved in 2018 when they introduced a single gene from Xerophyta viscosa – a resurrection plant also known as the small black-stick lily – into a variety of sweet potato. Known to be important in antioxidant defence, the gene, known as XvAld1, made these transgenic potato plants more resilient to a 12-day dehydration experiment. Compared to their wild-type neighbours, they remained greener for longer, lost fewer leaves, and grew taller even when deprived of water. Importantly, they were indistinguishable before the dehydration experiment began, suggesting the gene had no impact on growth or leaf structure.

Genes from resurrection plants have been shown to improve drought tolerance in other plants too, including the lab favourite Arabidopsis thaliana and tobacco plants. Still, with genetically-modified crops of any kind still required to fit stringent legal check-lists (particularly in the EU), Farrant has started to look for other ways to induce these remarkable traits of resurrection plants into crops grown today.

Just as the microbiome is a hot topic in human health, the root microbiome (or rhizosphere) is gaining interest in agricultural science. Drought tolerance might not be just in the leaves and stems, but in the roots. "This is where there might be [potential] for groups like resurrection plants or other extreme species," says George. "If there's a microbiome element to their ability to cope with extreme stress, then you might be able to transfer that into a cropping system much more easily than, say, genetic components."

And this is exactly what Farrant is trying to do. Along with her colleagues Shandry Tebele and Rose Marks, she has begun to map the microbiome of the Myrothamnus flabellifolia, a species that is unique even among resurrection plants. Growing in gravelly soil in South Africa, it can grow to waist-height and is more like a bush than a lonely patch of grass. Even with such complexity and size, it can survive for nine months or more without water.

The researchers first survey of M. flabellifolia's rhizosphere, published in 2024, revealed over 900 unique bacterial and fungal groups, the beginning of what might become a drought-tolerant probiotic that can be used for other plants. 

Aboveground, though, it is Farrant's work on teff that may be most auspicious. A naturally gluten-free cereal, teff has been grown for thousands of years in Ethiopia. Its tolerance to water scarcity has long led to it being lauded as a potential more sustainable and climate-resilient crop, but Farrant is interested in this species for slightly different reasons. Teff is the only crop that has a resurrection plant as a close relative: Eragrostis nindensis, a waist-height grass that grows on rocky slopes across southern Africa. Learning how these plants differ in their responses to drought might reveal which genes have been lost or switched off – and whether these can be reinserted back into teff, a genetic modification that is more likely to be successful given their close relationship.

It's a work still in its infancy. But already it seems that protection against sunlight is one of the main differences between the two. E. nindensi produces antioxidants inside its leaves and a coating of anthocyanins – essentially a plant's version of sun cream – on its external surfaces. Teff doesn't have this ability. It's a delicate balance for E. nindensi to pull off: sunlight is essential for a water-filled plant to grow, but during drought it can be lethal, leading to uncontrolled photosynthesis, the production of reactive oxygen species, and damage from UV radiation. For teff to have this option, however, might allow it to survive the harshest drought and grow another day.

So the tiny seeds of teff, milled to make flour for bread and pancakes, might just hold the key to a more sustainable agriculture. Just as maize, rice and wheat were bred for higher yields at the expense of resilience in the 20th Century's Green Revolution, such crops would add resilience, even if at the cost of a slightly lower yield. "They might have a low yield but the subsistence farmer has a crop," Farrant. "This is regardless of whether it rains in 10 days or two years."

* Alex Riley is science writer and author of Super Natural: How Life Thrives in Impossible Places. You can follow him on Instagram.

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