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Nanosensor can alert a smartphone when plants are stressed

Carbon nanotubes embedded in leaves detect chemical signals that are produced when a plant is damaged

Date:
April 15, 2020
Source:
Massachusetts Institute of Technology
Summary:
Engineers can closely track how plants respond to stresses such as injury, infection, and light damage using sensors made of carbon nanotubes. These sensors can be embedded in plant leaves, where they report on hydrogen peroxide levels.
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MIT engineers have developed a way to closely track how plants respond to stresses such as injury, infection, and light damage, using sensors made of carbon nanotubes. These sensors can be embedded in plant leaves, where they report on hydrogen peroxide signaling waves.

Plants use hydrogen peroxide to communicate within their leaves, sending out a distress signal that stimulates leaf cells to produce compounds that will help them repair damage or fend off predators such as insects. The new sensors can use these hydrogen peroxide signals to distinguish between different types of stress, as well as between different species of plants.

“Plants have a very sophisticated form of internal communication, which we can now observe for the first time. That means that in real-time, we can see a living plant’s response, communicating the specific type of stress that it’s experiencing,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT.

This kind of sensor could be used to study how plants respond to different types of stress, potentially helping agricultural scientists develop new strategies to improve crop yields. The researchers demonstrated their approach in eight different plant species, including spinach, strawberry plants, and arugula, and they believe it could work in many more.

Strano is the senior author of the study, which appears today in Nature Plants. MIT graduate student Tedrick Thomas Salim Lew is the lead author of the paper.

Embedded sensors

Over the past several years, Strano’s lab has been exploring the potential for engineering “nanobionic plants” — plants that incorporate nanomaterials that give the plants new functions, such as emitting light or detecting water shortages. In the new study, he set out to incorporate sensors that would report back on the plants’ health status.

Strano had previously developed carbon nanotube sensors that can detect various molecules, including hydrogen peroxide. About three years ago, Lew began working on trying to incorporate these sensors into plant leaves. Studies in Arabidopsis thaliana, often used for molecular studies of plants, had suggested that plants might use hydrogen peroxide as a signaling molecule, but its exact role was unclear.

Lew used a method called lipid exchange envelope penetration (LEEP) to incorporate the sensors into plant leaves. LEEP, which Strano’s lab developed several years ago, allows for the design of nanoparticles that can penetrate plant cell membranes. As Lew was working on embedding the carbon nanotube sensors, he made a serendipitous discovery.

“I was training myself to get familiarized with the technique, and in the process of the training I accidentally inflicted a wound on the plant. Then I saw this evolution of the hydrogen peroxide signal,” he says.

He saw that after a leaf was injured, hydrogen peroxide was released from the wound site and generated a wave that spread along the leaf, similar to the way that neurons transmit electrical impulses in our brains. As a plant cell releases hydrogen peroxide, it triggers calcium release within adjacent cells, which stimulates those cells to release more hydrogen peroxide.

“Like dominos successively falling, this makes a wave that can propagate much further than a hydrogen peroxide puff alone would,” Strano says. “The wave itself is powered by the cells that receive and propagate it.”

This flood of hydrogen peroxide stimulates plant cells to produce molecules called secondary metabolites, such as flavonoids or carotenoids, which help them to repair the damage. Some plants also produce other secondary metabolites that can be secreted to fend off predators. These metabolites are often the source of the food flavors that we desire in our edible plants, and they are only produced under stress.

A key advantage of the new sensing technique is that it can be used in many different plant species. Traditionally, plant biologists have done much of their molecular biology research in certain plants that are amenable to genetic manipulation, including Arabidopsis thaliana and tobacco plants. However, the new MIT approach is applicable to potentially any plant.

“In this study, we were able to quickly compare eight plant species, and you would not be able to do that with the old tools,” Strano says.

The researchers tested strawberry plants, spinach, arugula, lettuce, watercress, and sorrel, and found that different species appear to produce different waveforms — the distinctive shape produced by mapping the concentration of hydrogen peroxide over time. They hypothesize that each plant’s response is related to its ability to counteract the damage. Each species also appears to respond differently to different types of stress, including mechanical injury, infection, and heat or light damage.

“This waveform holds a lot of information for each species, and even more exciting is that the type of stress on a given plant is encoded in this waveform,” Strano says. “You can look at the real time response that a plant experiences in almost any new environment.”

Stress response

The near-infrared fluorescence produced by the sensors can be imaged using a small infrared camera connected to a Raspberry Pi, a $35 credit-card-sized computer similar to the computer inside a smartphone. “Very inexpensive instrumentation can be used to capture the signal,” Strano says.

Applications for this technology include screening different species of plants for their ability to resist mechanical damage, light, heat, and other forms of stress, Strano says. It could also be used to study how different species respond to pathogens, such as the bacteria that cause citrus greening and the fungus that causes coffee rust.

“One of the things I’m interested in doing is understanding why some types of plants exhibit certain immunity to these pathogens and others don’t,” he says.

Strano and his colleagues in the Disruptive and Sustainable Technology for Agricultural Precision interdisciplinary research group at the MIT-Singapore Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, are also interested in studying is how plants respond to different growing conditions in urban farms.

One problem they hope to address is shade avoidance, which is seen in many species of plants when they are grown at high density. Such plants turn on a stress response that diverts their resources into growing taller, instead of putting energy into producing crops. This lowers the overall crop yield, so agricultural researchers are interested in engineering plants so that don’t turn on that response.

“Our sensor allows us to intercept that stress signal and to understand exactly the conditions and the mechanism that are happening upstream and downstream in the plant that gives rise to the shade avoidance,” Strano says.

The research was funded by the National Research Foundation of Singapore, the Singapore Agency for Science, Technology, and Research (A*STAR), and the U.S. Department of Energy Computational Science Graduate Fellowship Program.


Story Source:

Materials provided by Massachusetts Institute of Technology. Original written by Anne Trafton. Note: Content may be edited for style and length.


Journal Reference:

  1. Tedrick Thomas Salim Lew, Volodymyr B. Koman, Kevin S. Silmore, Jun Sung Seo, Pavlo Gordiichuk, Seon-Yeong Kwak, Minkyung Park, Mervin Chun-Yi Ang, Duc Thinh Khong, Michael A. Lee, Mary B. Chan-Park, Nam-Hai Chua, Michael S. Strano. Real-time detection of wound-induced H2O2 signalling waves in plants with optical nanosensors. Nature Plants, 2020; 6 (4): 404 DOI: 10.1038/s41477-020-0632-4

Cite This Page:

Massachusetts Institute of Technology. “Nanosensor can alert a smartphone when plants are stressed: Carbon nanotubes embedded in leaves detect chemical signals that are produced when a plant is damaged.” ScienceDaily. ScienceDaily, 15 April 2020. <www.sciencedaily.com/releases/2020/04/200415133512.htm>.

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basmati-farmer

A farmer in Jind, Haryana in his  basmati paddy field. (Express photo: Renuka Puri)

Pesticide residues are an issue, more so when it concerns products such as basmati rice, fetching the country annual export revenues ranging from $ 3.23 billion in 2016-17 to $ 4.52 billion in 2014-15. The burden of consignments being rejected ultimately falls on the farmer, who has to, then, use new-generation pesticides that are safer, but costlier and very often proprietary/patented molecules.

The most recent example is of Tricyclazole. A single 120-gram spray of this common fungicide, against leaf and neck blast disease in paddy, hardly costs Rs 150-170 per acre. But with the European Union (EU) deciding not to allow import of any rice having Tricyclazole levels above 0.01 parts per million (ppm) from January 1, farmers would find it difficult to spray the generic chemical sold under assorted brands like ‘Sivic’, ‘Baan’ and ‘Beam’. The existing tolerance limit stipulated by the EU (which accounts for about 3.5 lakh tonnes of India’s total annual basmati shipments of 40 lakh tonnes) for Tricyclazole is one ppm or 1 mg/kg; 0.01 ppm will make it 1mg/100 kg!

With Tricyclazole ruled out, farmers may, henceforth, have to go for fungicides that are considered environmentally friendlier, though costing ten times more. These include Azoxystrobin (a single 200-ml spray, sold under the Swiss company Syngenta’s ‘Amistar’ brand, costs around Rs 900 per acre) and Picoxystrobin (the cost of a single 400-ml spray of this formulation, sold under DuPont’s ‘Galileo’ brand, comes to Rs 1,300 per acre). No less expensive is ‘Nativo’. This combination fungicide of Bayer CropScience, containing Tebuconazole and Trifloxystrobin, costs Rs 1,000 for a single 160-gram spray per acre.

However, an alternative approach to pesticide application — necessary, especially keeping in view basmati’s premium quality attributes and huge export market — is to “breed for disease resistance”. This involves transfer of specific disease-resistance genes, from both traditional landrace cultivars and wild relatives of paddy, into existing high-yielding basmati varieties. That is what scientists at the Indian Agricultural Research Institute (IARI) have sought to do.

The New Delhi-based institute — under a collaborative project with the Indian Council of Agricultural Research’s National Research Centre on Plant Biotechnology — has transferred the ‘Pi9’ gene into its popular Pusa Basmati-1 variety. This gene, sourced from Oryza minuta (a wild relative of Oryza sativa, which is the normal cultivated paddy), provides “very high resistance” against leaf blast and “moderate resistance” against neck blast fungus.

The resultant variety, which is called Pusa Basmati-1637, combines Pusa Basmati-1’s high-yielding trait with resistance against a fungus that infests the leaf and neck nodes of the rice plant’s main stem, from where the grain-bearing earheads (panicles) emerge. Blast disease affecting the leaf basically damages the chlorophyll, thereby impeding photosynthesis that involves absorption of sunlight and using its energy to synthesise carbohydrates. Neck blast, if severe, can cause the stem to even break. If the panicles at that point have only partially formed grains, in their early milky stage, the yield losses can be huge.

Rajeev Kharb, a farmer from Tito Kheri village in Safidon tehsil of Haryana’s Jind district, has grown Pusa Basmati-1637 in five out of his total 80-acre holding. The latter includes 28 acres of own and 52 acres of leased land. High temperatures and humidity levels this time round has resulted in the bulk of his planted area – mainly under Pusa Basmati-1401, Pusa Basmati-1 and Pusa Basmati-1509 – suffering gardan-marod (the local term for blast, whose literal translation is “curling of the neck”) to the extent of 10-20 per cent.

“But nothing has happened to my Pusa Basmati-1637 field. This, even without spraying any Tricyclazole,” says Kharb. A loss of 10-20 per cent isn’t small. Taking per-acre yields of 22-25 quintals for Pusa Basmati-1, 25-28 quintals for Pusa Basmati-1509 and 28-30 quintals for Pusa Basmati-1401, and current average price realisations of Rs 2,800/quintal, it works out to anywhere from Rs 7,000 to Rs 14,000 per acre.

“We will continue to have to spray for other diseases (bacterial blight and sheath blight fungus) and pests (brown plant hopper and stem borer). But with this new variety, there is still significant savings from not using Tricyclazole or other expensive fungicides against blast,” points out Pritam Singh Hanjra, a progressive farmer from Urlana Khurd village in Madlauda tehsil of Panipat district.

Hanjra, who has sown Pusa Basmati-1637 in five out of his 105-acre holding (30 acres own and the rest leased), estimates expenses on crop protection chemicals at Rs 3,000-4,000 out of the total cultivation costs of Rs 20,000-22,000 per acre for paddy. “It can go up, depending on the extent of pest and disease incidence. Either way, this is the second biggest expenditure head after manual harvesting-and-threshing (Rs 4,500-5,000), and more than fertilizers (Rs 2,100-2,200),” he claims.

A K Singh, head of IARI’s Division of Genetics, notes that Indian breeders have, over a period, managed to raise crop yields. The traditional tall basmati cultivars, for instance, gave barely 8-10 quintals of paddy per acre. With improved dwarf high-yielding basmati varieties, these have gone up to 25 quintals or so. “Our challenge now is to protect these yields and preferably through breeding for resistance, as opposed to pesticide application,” he adds.

IARI is, in fact, working on transferring other blast resistance genes as well — such as ‘Pi54’, ‘Pi25’, ‘Pi2’ and ‘Pib’, all from wild relatives and land races of rice — to high-yielding basmati varieties.

“We want to do pyramiding of these genes (combining two or more of them), in order to impart more durable resistance against blast. Besides, we have already developed and released two new varieties, Pusa Basmati-1718 and Pusa Basmati-1728, both of them incorporating the Xa21 and xa13 genes that confer resistance to the bacterial blight pathogen. The first variety is basically Pusa Basmati-1121 and the second one Pusa Basmati-1401, containing both these genes obtained from Oryza longistaminata (another wild relative of paddy) and BJ1 (a traditional land race), respectively,” informs Singh.

 

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Startups focus on the microbiome as an organic solution to increase crop yields

 

One of the multi-billion dollar problems facing the world these days is how to grow more food.

As the planet approaches adding another billion or more people, and as an increasing number of those people are wealthier than they’ve been before, the question of where our food comes from and how we raise it becomes more than an academic discussion, as farming is 10 percent of the world economy.

Venture investors, who are never known to shy away from throwing money at technological solutions for multi-billion dollar problems, have increasingly been turning their attention to the ag market.

These bets encompass everything from big data technologies to new sensing equipment, and… now… the study of the microbial life that surrounds all the things that grow in the dirt.

Biome science (as Vinod Khosla has told me) is an incredibly exciting area for investors to pursue, and one of the prime beneficiaries of this attention is a company in St. Louis called NewLeaf Symbiotics.

In fact, St. Louis is an emerging hub for all sorts of food and agricultural investment activity (a story for another time).

NewLeaf, which just closed on $6 million in new money to round out a $30 million round of funding, is one of a number of companies working at the forefront of agricultural technology research into the plant biome.

“There are going to be multiple winners in the category. It’s such a broad area,” says Sanjeev Krishnan, a managing director of S2G Ventures, an agriculture and food-focused fund whose main investor is the Walton family. “There are more things living under soil than on the surface of the entire planet, [so] there’s a lot of opportunity to figure out causality.”

For NewLeaf, the discovery of a bacteria that is found on pretty much everything that grows in the soil was the “eureka” moment that led to the company’s commercialization of technologies to ensure aspects of crop health.

It’s also what attracted S2G Ventures and The Yard, a fund comprised of Harvard alums that invest in companies with a connection to the university (in this case, the CFO is a Harvard graduate).

NewLeaf’s new round comes at a critical time for the company. It’s tripled the size of its R&D facility in St. Louis and is about to bring its first products to market.

The company’s first magic microbe is an additive to soybean seeds called rhizobia, and their second is a treatment for peanuts. Both are designed to make the seeds more resistant to disease and better able to withstand certain environmental conditions.

What makes all of this so compelling to both investors and big ag companies is the fact that none of these treatments involve genetic modification.

The bacteria are naturally occurring, and part of the special sauce to NewLeaf’s tech is the company’s index of thousands of different bacteria and their effects on plants, according to chief executive Tom Laurita.

“These bacteria are cost-free to the plant, because they use biological byproducts,” he says. “In some cases the bacteria are protection against a disease or predation. There might be a disease that an insect could turn into a viral disease in a particular plant, but bacteria could make that microbial disease harmless.

As S2G joins the company’s cap table, Laurita says it’s yet another sign that the technology is maturing and that companies from Monsanto (an earlier investor) to Walmart (through the Walton family’s fund) are recognizing the benefits of biome science.

“We’re at this nexus between the ag industry looking for cutting edge innovative, natural sustainable products and the consumer looking for the same thing,” Laurita tells me. “It’s the first time these two groups have invested in the same company. It’s a harbinger of how investment in ag and food might be changing.”

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EurekAlert

Public Release: 10-Aug-2017

Blocking pathogens in rice

Düsseldorf plant researchers funded by Bill & Melinda Gates Foundation

Heinrich-Heine University Duesseldorf

IMAGE
IMAGE: Rice plants; the research group led by Wolf B. Frommer wants to make rice resistant to the harmful rice blight that endangers rice harvests in Africa and South-East Asia. view more 

Credit: Wolf B. Frommer

What is known as “rice blight” is a dreaded plant disease that endangers rice harvests throughout the whole of South-East Asia, especially India, as well as large parts of Africa and can thus lead to great hardship amongst the local population. The disease is caused by the bacterial pathogen Xanthomonas oryzae oryzae.

Professor Wolf B. Frommer, plant researcher at the Institute of Mo-lecular Physiology at HHU, has assembled an international research group to fight rice blight. The team includes scientists from Iowa State University and the University of Florida in the USA, the Institut de Recherche pour le Développement in Montpellier, France, Colombia’s International Centre for Tropical Agriculture and the International Rice Research Institute in the Philippines. The researchers have found a way to make plants resistant to the pathogen.

Frommer is an expert on transport processes in plants. The sugar transporters known as SWEET identified by his research group play a key role in resistance. Plants need these transporters to bring the sugar produced during photosynthesis in the leaves to the seeds. And it is precisely this transport mechanism that the pathogens re-programme for their own purposes.

In independent studies, US-American researchers Professor Bing Yang and Professor Frank White (now at Iowa State University and the University of Florida) discovered that a protein (which later transpired to be SWEET) is responsible for plants’ resistance to rice blight. Joint trials then revealed that the bacteria systematically activate the transporters in the rice cells and in so doing gain access to nutrients. If such activation is prevented, the bacteria cannot multiply.

Wolf B. Frommer says: “This surprising discovery has provided us with a strategy for our joint research project: We cut off the pathogens’ route to their larder – the plants’ sugar stores – and starve them out.”

The research project “Transformative Strategy for Controlling Rice Disease in Developing Countries” began on 1 August 2017. The project is supported by a four-year grant from the Bill & Melinda Gates Foundation. In the framework of the project, Frommer will concentrate especially on the production of elite varieties for India and Africa. He will mostly conduct his research work within the working group led by Dr. Joon Seob Eom at the Max Planck Institute for Plant Breeding Research in Cologne.

The research results can prove valuable beyond the specific topic of rice blight. Wolf B. Frommer: “Our discovery might be just the tip of the iceberg. We could use the same approach to try and combat other plant diseases and in that way hopefully make a small contribution to protecting the world’s food supply.” And that would also be good for the climate and the environment, since if plant diseases can be combatted effectively, less pesticides and fertilisers would be needed worldwide to ensure sufficient harvests.

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Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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MILTECH

Fires, storms, insects: climate change increases risks for forests worldwide

“When climate is changing, there are initially direct effects on the growth of the trees. But the chain of climate impacts is considerably longer: if, for instance, more rain saturates the soils or if soils are less frequently frozen, the trees will have less stability to withstand storms and damage will increase. The many dead and dying trees will then provide ideal breeding material for insects such as bark beetles to reproduce quickly. At the same time, the trees that are still alive will be weakened and will thus be more vulnerable to insect attacks,” explains lead author Rupert Seidl from the University of Natural Resources and Life Sciences in Vienna. “Our study shows that climate change significantly influences disruptive factors all around the world – and that a further increase of disturbances in forests has to be expected in the future.”

Stress is normal for the forests – while the increase of disturbances is not

“Whether in the giant boreal forests of Scandinavia and Russia or in the wide woodlands of North America – fundamentally, natural disturbances like fires, insect attacks or storms are normal aspects of these ecosystems,” says project leader Christopher Reyer of the Potsdam Institute for Climate Impact Research. To get shaken up a little through natural disturbances can even be good for forests, as the natural renewal for instance promotes a greater biological diversity.

“But through climate change, these usual disturbances have already changed in the last years”, explains Reyer. “This has impacts on the ability of the forests to provide services for us humans – for example in terms of their wood, in terms of protection against avalanches, or simply as recreational spaces. If climate change keeps on increasing disturbances, this clearly is a risk for the coping capacities of the forests – in the long run, ecosystems as we know them today might change profoundly.”

Climate change as a challenge for forest management

For the review study, forest experts from Austria, Germany, Switzerland, Finland, Italy, Spain, the Czech Republic, Scotland, Slovakia and Slovenia analyzed more than 1600 different findings from academic publications which establish links between disruptions and climate factors. Additionally, the scientists examined how indirect climate impacts, such as the alteration of tree species in the forests, influence the occurrence of disturbances. In particular the indirect effects and the interactions between different disruptive factors were collated in an unprecedentedly comprehensive manner in the research on forest disturbances.

Already today it is clear that risks caused by fires, pests and fungi will increase in the context of climate change – the devastating forest fires in Canada and Russia in the last years are an example of possible impacts. Fires are currently the most significant disruptive factor in many forests around the world, and will become an even more serious threat in the coming decades, according to the scientists. The forests of Northern and Central Europe, however, have until present primarily been impaired by storms such as Cyclone Kyrill in 2007, and the insect damage that follows them – a type of damage which will also increase under climate change. Damage caused by ice and snow were the only disruptive factors examined by the study that will likely decrease under continuing climate change. However, this positive effect cannot compensate the negative effects from other factors.

“Our analysis clearly shows that climate change brings enormous challenges for forests – the forest sector has to adapt and to increase its resilience, as it seems impossible to prevent damage completely”, says Seidl. “In the long term, reductions of greenhouse-gas emissions and effective climate protection measures will help the most,” adds Reyer.

Article:  Rupert Seidl, Dominik Thom, Markus Kautz, Dario Martin-Benito, Mikko Peltoniemi, Giorgio Vacchiano, Jan Wild, Davide Ascoli, Michal Petr, Juha Honkaniemi, Manfred J. Lexer, Volodymyr Trotsiuk, Paola Mairota, Miroslav Svoboda, Marek Fabrika, Thomas A. Nagel, and Christopher P. O. Reyer (2017): Forest disturbances under climate change. Nature Climate Change [10.1038/NCLIMATE3303]

Weblink to the article: https://www.nature.com/nclimate/journal/v7/n6/full/nclimate3303.html

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