Category Archives: agriculture

Controlling agricultural pests with CRISPR-based technology

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CRISPR (clustered regularly interspaced short palindromic repeats) technology is often touted as being ‘precise’, which as far as I can tell, is not exactly the case (see my Nov. 28, 2018 posting about the CRISPR babies [scroll down about 30% of the way for the first hint that CRISPR isn’t]). So, it’s a bit odd to see the word ‘precise’ used as part of a new CRISPR-based technology’s name (from a January 8, 2019 news item on ScienceDaily,

Using the CRISPR gene editing tool, Nikolay Kandul, Omar Akbari and their colleagues at UC San Diego [UC is University of California] and UC Berkeley devised a method of altering key genes that control insect sex determination and fertility.

A description of the new “precision-guided sterile insect technique,” [emphasis mine] or pgSIT, is published Jan. 8 [2019] in the journal Nature Communications.

A January 8, 209 UCSD press release (also on EurekAlert) by Mario Aguilera, which originated the news item, delves further into the research,

When pgSIT-derived eggs are introduced into targeted populations, the researchers report, only adult sterile males emerge, resulting in a novel, environmentally friendly and relatively low-cost method of controlling pest populations in the future.

“CRISPR technology has empowered our team to innovate a new, effective, species-specific, self-limiting, safe and scalable genetic population control technology with remarkable potential to be developed and utilized in a plethora of insect pests and disease vectors,” said Akbari, an assistant professor in UC San Diego’s Division of Biological Sciences. “In the future, we strongly believe this technology will be safely used in the field to suppress and even eradicate target species locally, thereby revolutionizing how insects are managed and controlled going forward.”

Since the 1930s, agricultural researchers have used select methods to release sterile male insects into the wild to control and eradicate pest populations. In the 1950s, a method using irradiated males was implemented in the United States to eliminate the pest species known as the New World Screwworm fly, which consumes animal flesh and causes extensive damage to livestock. Such radiation-based methods were later used in Mexico and parts of Central America and continue today.

Instead of radiation, the new pgSIT (precision-guided sterile insect technique), developed over the past year-and-a-half by Kandul and Akbari in the fruit fly Drosophila, uses CRISPR to simultaneously disrupt key genes that control female viability and male fertility in pest species. pgSIT, the researchers say, results in sterile male progeny with 100 percent efficiency. Because the targeted genes are common to a vast cross-section of insects, the researchers are confident the technology can be applied to a range of insects, including disease-spreading mosquitoes.

The researchers envision a system in which scientists genetically alter and produce eggs of a targeted pest species. The eggs are then shipped to a pest location virtually anywhere in the world, circumventing the need for a production facility on-site. Once the eggs are deployed at the pest location, the researchers say, the newly born sterile males will mate with females in the wild and be incapable of producing offspring, driving down the population.

“This is a novel twist of a very old technology,” said Kandul, an assistant project scientist in UC San Diego’s Division of Biological Sciences. “That novel twist makes it extremely portable from one species to another species to suppress populations of mosquitoes or agricultural pests, for example those that feed on valuable wine grapes.”

The new technology is distinct from continuously self-propagating “gene drive” systems that propagate genetic alterations from generation to generation. Instead, pgSIT is considered a “dead end” since male sterility effectively closes the door on future generations.

“The sterile insect technique is an environmentally safe and proven technology,” [emphasis mine] the researchers note in the paper. “We aimed to develop a novel, safe, controllable, non-invasive genetic CRISPR-based technology that could be transferred across species and implemented worldwide in the short-term to combat wild populations.”

With pgSIT proven in fruit flies, the scientists are hoping to develop the technology in Aedes aegypti, the mosquito species responsible for transmitting dengue fever, Zika, yellow fever and other diseases to millions of people.

“The extension of this work to other insect pests could prove to be a general and very useful strategy to deal with many vector-borne diseases that plague humanity and wreak havoc an agriculture globally,” said Suresh Subramani, global director of the Tata Institute for Genetics and Society.

I have one comment about the ‘safety’ of the sterile insect technique. It’s been safe up until now but, assuming this technique works as described: What happens as this new and more powerful technique is more widely deployed possibly eliminating whole species of insects? Might these ‘pests’ have a heretofore unknown beneficial effect somewhere in the food chain or in an ecosystem? Or, there may be other unintended consequences.

Moving on, here’s a link to and a citation for the paper,

Transforming insect population control with precision guided sterile males with demonstration in flies by Nikolay P. Kandul, Junru Liu, Hector M. Sanchez C., Sean L. Wu, John M. Marshall, & Omar S. Akbari. Nature Communications volume 10, Article number: 84 (2019) DOI: https://doi.org/10.1038/s41467-018-07964-7 Published 08 January 2019

This paper is open access.

The researchers have made this illustrative image available,

Caption: This is a schematic of the new precision-guided sterile insect technique (pgSIT), which uses components of the CRISPR/Cas9 system to disrupt key genes that control female viability and male fertility, resulting in sterile male progeny. Credit: Nikolay Kandul, Akbari Lab, UC San Diego

Real-time tracking of UV (ultraviolet light) exposure for all skin types (light to dark)

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It’s nice to find this research after my August 21, 2018 posting where I highlighted (scroll down to ‘Final comments’) the issues around databases and skin cancer data which is usually derived from fair-skinned people while people with darker hues tend not to be included. This is partly due to the fact that fair-skinned people have a higher risk and also partly due to myths about how more melanin in your skin somehow protects you from skin cancer.

This October 4, 2018 news item on ScienceDaily announces research into a way to track UV exposure for all skin types,

Researchers from the University of Granada [Spain] and RMIT University in Melbourne [Australia] have developed personalised and low-cost wearable ultraviolet (UV) sensors that warn users when their exposure to the sun has become dangerous.

The paper-based sensor, which can be worn as a wristband, features happy and sad emoticon faces — drawn in an invisible UV-sensitive ink — that successively light up as you reach 25%, 50%, 75% and finally 100% of your daily recommended UV exposure.

The research team have also created six versions of the colour-changing wristbands, each of which is personalised for a specific skin tone  [emphasis mine]– an important characteristic given that darker people need more sun exposure to produce vitamin D, which is essential for healthy bones, teeth and muscles.

An October 2, 2018 University of Granada press release (also on EurekAlert) delves further,

Four of the wristbands, each of which indicates a different stage of exposure to UV radiation (25%, 50%, 75% and 100%)

The emoticon faces on the wristband successively “light up” as exposure to UV radiation increases

Skin cancer, one of the most common types of cancer throughout the world, is primarily caused by overexposure to ultraviolet radiation (UVR). In Spain, over 74,000 people are diagnosed with non-melanoma skin cancer every year, while a further 4,000 are diagnosed with melanoma skin cancer. In regions such as Australia, where the ozone layer has been substantially depleted, it is estimated that approximately 2 in 3 people will be diagnosed with skin cancer by the time they reach the age of 70.

“UVB and UVC radiation is retained by the ozone layer. This sensor is especially important in the current context, given that the hole in the ozone layer is exposing us to such dangerous radiation”, explains José Manuel Domínguez Vera, a researcher at the University of Granada’s Department of Inorganic Chemistry and the main author of the paper.

Domínguez Vera also highlights that other sensors currently available on the market only measure overall UV radiation, without distinguishing between UVA, UVB and UVC, each of which has a significantly different impact on human health.  In contrast, the new paper-based sensor can differentiate between UVA, UVB and UVC radiation. Prolonged exposure to UVA radiation is associated with skin ageing and wrinkling, while excessive exposure to UVB causes sunburn and increases the likelihood of skin cancer and eye damage.

Drawbacks of the traditional UV index

Ultraviolet radiation is determined by aspects such as location, time of day, pollution levels, astronomical factors, weather conditions such as clouds, and can be heightened by reflective surfaces like bodies of water, sand and snow. But UV rays are not visible to the human eye (even if it is cloudy UV radiation can be high) and until now the only way of monitoring UV intensity has been to use the UV index, which is standardly given in weather reports and indicates 5 degrees of radiation;  low, moderate, high, very high or extreme.

Despite its usefulness, the UV index is a relatively limited tool. For instance, it does not clearly indicate what time of the day or for how long you should be outside to get your essential vitamin D dose, or when to cover up to avoid sunburn and a heightened risk of skin cancer.

Moreover, the UV index is normally based on calculations for fair skin, making it unsuitable for ethnically diverse populations.  While individuals with fairer skin are more susceptible to UV damage, those with darker skin require much longer periods in the sun in order to absorb healthy amounts of vitamin D. In this regard, the UV index is not an accurate tool for gauging and monitoring an individual’s recommended daily exposure.

UV-sensitive ink

The research team set out to tackle the drawbacks of the traditional UV index by developing an inexpensive, disposable and personalised sensor that allows the wearer to track their UV exposure in real-time. The sensor paper they created features a special ink, containing phosphomolybdic acid (PMA), which turns from colourless to blue when exposed to UV radiation. They can use the initially-invisible ink to draw faces—or any other design—on paper and other surfaces. Depending on the type and intensity of the UV radiation to which the ink is exposed, the paper begins to turn blue; the greater the exposure to UV radiation, the faster the paper turns blue.

Additionally, by tweaking the ink composition and the sensor design, the team were able to make the ink change colour faster or slower, allowing them to produce different sensors that are tailored to the six different types of skin colour. [emphasis mine]

Applications beyond health

This low-cost, paper-based sensor technology will not only help people of all colours to strike an optimum balance between absorbing enough vitamin D and avoiding sun damage — it also has significant applications for the agricultural and industrial sectors. UV rays affect the growth of crops and the shelf life of a range of consumer products. As the UV sensors can detect even the slightest doses of UV radiation, as well as the most extreme, this new technology could have vast potential for industries and companies seeking to evaluate the prolonged impact of UV exposure on products that are cultivated or kept outdoors.

The research project is the result of fruitful collaborations between two members of the UGR BIONanoMet (FQM368) research group; Ana González and José Manuel Domínguez-Vera, and the research group led by Dr. Vipul Bansal at RMIT University in Melbourne (Australia).

Here’s a link to and a citation for the paper,

Skin color-specific and spectrally-selective naked-eye dosimetry of UVA, B and C radiations by Wenyue Zou, Ana González, Deshetti Jampaiah, Rajesh Ramanathan, Mohammad Taha, Sumeet Walia, Sharath Sriram, Madhu Bhaskaran, José M. Dominguez-Vera, & Vipul Bansal. Nature Communicationsvolume 9, Article number: 3743 (2018) DOI: https://doi.org/10.1038/s41467-018-06273-3 Published 25 September 2018

This paper is open access.

Altered virus spins gold into beads

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They’re not calling this synthetic biology but I’ m pretty sure that altering a virus gene so the virus can spin gold (Rumpelstiltskin anyone?) qualifies. From an August 24, 2018 news item on ScienceDaily,

The race is on to find manufacturing techniques capable of arranging molecular and nanoscale objects with precision.

Engineers at the University of California, Riverside, have altered a virus to arrange gold atoms into spheroids measuring a few nanometers in diameter. The finding could make production of some electronic components cheaper, easier, and faster.

An August 23, 2018 University of California at Riverside (UCR) news release (also on EurekAlett) by Holly Ober, which originated the news item, adds detail,

“Nature has been assembling complex, highly organized nanostructures for millennia with precision and specificity far superior to the most advanced technological approaches,” said Elaine Haberer, a professor of electrical and computer engineering in UCR’s Marlan and Rosemary Bourns College of Engineering and senior author of the paper describing the breakthrough. “By understanding and harnessing these capabilities, this extraordinary nanoscale precision can be used to tailor and build highly advanced materials with previously unattainable performance.”

Viruses exist in a multitude of shapes and contain a wide range of receptors that bind to molecules. Genetically modifying the receptors to bind to ions of metals used in electronics causes these ions to “stick” to the virus, creating an object of the same size and shape. This procedure has been used to produce nanostructures used in battery electrodes, supercapacitors, sensors, biomedical tools, photocatalytic materials, and photovoltaics.

The virus’ natural shape has limited the range of possible metal shapes. Most viruses can change volume under different scenarios, but resist the dramatic alterations to their basic architecture that would permit other forms.

The M13 bacteriophage, however, is more flexible. Bacteriophages are a type of virus that infects bacteria, in this case, gram-negative bacteria, such as Escherichia coli, which is ubiquitous in the digestive tracts of humans and animals. M13 bacteriophages genetically modified to bind with gold are usually used to form long, golden nanowires.

Studies of the infection process of the M13 bacteriophage have shown the virus can be converted to a spheroid upon interaction with water and chloroform. Yet, until now, the M13 spheroid has been completely unexplored as a nanomaterial template.

Haberer’s group added a gold ion solution to M13 spheroids, creating gold nanobeads that are spiky and hollow.

“The novelty of our work lies in the optimization and demonstration of a viral template, which overcomes the geometric constraints associated with most other viruses,” Haberer said. “We used a simple conversion process to make the M13 virus synthesize inorganic spherical nanoshells tens of nanometers in diameter, as well as nanowires nearly 1 micron in length.”

The researchers are using the gold nanobeads to remove pollutants from wastewater through enhanced photocatalytic behavior.

The work enhances the utility of the M13 bacteriophage as a scaffold for nanomaterial synthesis. The researchers believe the M13 bacteriophage template transformation scheme described in the paper can be extended to related bacteriophages.

Here’s a link to and a citation for the paper,

M13 bacteriophage spheroids as scaffolds for directed synthesis of spiky gold nanostructures by Tam-Triet Ngo-Duc, Joshua M. Plank, Gongde Chen, Reed E. S. Harrison, Dimitrios Morikis, Haizhou Liu, and Elaine D. Haberer. Nanoscale, 2018,10, 13055-13063 DOI: 10.1039/C8NR03229G First published on 25 Jun 2018

This paper is behind a paywall.

For another example of genetic engineering and synthetic biology, see my July 18, 2018 posting: Genetic engineering: an eggplant in Bangladesh and a synthetic biology grant at Concordia University (Canada).

For anyone unfamiliar with the Rumpelstiltskin fairytale about spinning straw into gold, see its Wikipedida entry.

Terahertz imagers at your fingertips

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It seems to me that I stumbled across quite a few carbon nanotube (CNT) stories in 2018. This one comes courtesy of Japan (from a June 28, 2018 news item on Nanowerk),

Researchers at Tokyo Tech have developed flexible terahertz imagers based on chemically “tunable” carbon nanotube materials. The findings expand the scope of terahertz applications to include wrap-around, wearable technologies as well as large-area photonic devices.

Here’s a peek at an imager,

Figure 1. The CNT-based flexible THz imager (a) Resting on a fingertip, the CNT THz imager can easily wrap around curved surfaces. (b) Just by inserting and rotating a flexible THz imager attached to the fingertip, damage to a pipe was clearly detected. Courtesy Tokyo Tech

A June 28, 2018 Tokyo Tech Institute press release (also on Eurekalert), which originated the news item, provides more detail,

Carbon nanotubes (CNTs) are beginning to take the electronics world by storm, and now their use in terahertz (THz) technologies has taken a big step forward.

Due to their excellent conductivity and unique physical properties, CNTs are an attractive option for next-generation electronic devices. One of the most promising developments is their application in THz devices. Increasingly, THz imagers are emerging as a safe and viable alternative to conventional imaging systems across a wide range of applications, from airport security, food inspection and art authentication to medical and environmental sensing technologies.

The demand for THz detectors that can deliver real-time imaging for a broad range of industrial applications has spurred research into low-cost, flexible THz imaging systems. Yukio Kawano of the Laboratory for Future Interdisciplinary Research of Science and Technology, Tokyo Tech, is a world-renowned expert in this field. In 2016, for example, he announced the development of wearable terahertz technologies based on multiarrayed carbon nanotubes.

Kawano and his team have since been investigating THz detection performance for various types of CNT materials, in recognition of the fact that there is plenty of room for improvement to meet the needs of industrial-scale applications.

Now, they report the development of flexible THz imagers for CNT films that can be fine-tuned to maximize THz detector performance.

Publishing their findings in ACS Applied Nano Materials, the new THz imagers are based on chemically adjustable semiconducting CNT films.

By making use of a technology known as ionic liquid gating1, the researchers demonstrated that they could obtain a high degree of control over key factors related to THz detector performance for a CNT film with a thickness of 30 micrometers. This level of thickness was important to ensure that the imagers would maintain their free-standing shape and flexibility, as shown in Figure 1 [see above].

“Additionally,” the team says, “we developed gate-free Fermi-level2 tuning based on variable-concentration dopant solutions and fabricated a Fermi-level-tuned p-n junction3 CNT THz imager.” In experiments using this new type of imager, the researchers achieved successful visualization of a metal paper clip inside a standard envelope (see Figure 2.)

Non-contact, non-destructive visualization

Figure 2. Non-contact, non-destructive visualization

The CNT THz imager enabled clear, non-destructive visualization of a metal paper clip inside an envelope.

The bendability of the new THz imager and the possibility of even further fine-tuning will expand the range of CNT-based devices that could be developed in the near future.

Moreover, low-cost fabrication methods such as inkjet coating could make large-area THz imaging devices more readily available.

1 Ionic liquid gating

A technique used to modulate a material’s charge carrier properties.

2 Fermi level

A measure of the electrochemical potential for electrons, which is important for determining the electrical and thermal properties of solids. The term is named after the Italian–American physicist Enrico Fermi.

3 p-n junction

Refers to the interface between positive (p-type) and negative (n-type) semiconducting materials. These junctions form the basis of semiconductor electronic devices.

Here’s a link to and a citation for the paper,

Fermi-Level-Controlled Semiconducting-Separated Carbon Nanotube Films for Flexible Terahertz Imagers by Daichi Suzuki, Yuki Ochiai, Yota Nakagawa, Yuki Kuwahara, Takeshi Saito, and Yukio Kawano. ACS Appl. Nano Mater., 2018, 1 (6), pp 2469–2475 DOI: 10.1021/acsanm.8b00421 Publication Date (Web): June 6, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

Therapeutic nanoparticles for agricultural crops

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Nanoscale drug delivery systems developed by the biomedical community may prove useful to farmers. The Canadian Broadcasting Corporation (CBC) featured the story in a May 26, 2018 online news item (with audio file; Note: A link has been removed),

Thanks to a fortuitous conversation between an Israeli chemical engineer who works on medical nanotechnology and his farmer friend, there’s a new way to deliver nourishment to nutrient-starved crops.

Avi Schroeder, the chemical engineer and cancer researcher from Technion — Israel Institute of Technology asked his friend what are the major problems facing agriculture today. “He said, ‘You know Avi, one of the major issues we’re facing is that in some of the crops we try to grow, we actually have a lack of nutrients. And then we end up not growing those crops even though they’re very valuable or very important crops.'”

This problem is only going to become more acute in many regions of the world as global population approaches eight billion people.

“Feeding them with healthy food and nutritious food is becoming a major limiting factor. And … the land we can actually grow crops on are also becoming smaller and smaller in every country because people need to build houses too. So what we want is to get actually more crops per hectare.”

The way farmers currently deliver nutrients to malnourished agricultural crops is very inefficient. Much of what is added to the leaves of the plant is wasted. Most of it washes away or isn’t taken up by the plants.

If plants don’t get the nutrients they need, their leaves start to yellow, their growth becomes stunted and they don’t produce as much food as nutrient-rich crops.

…

“We work primarily in the field of medicine,” says Schroeder. “What we do many times is we’ll load minuscule doses of medicine into nanoparticles — we’ll inject them into the patient. And those nanoparticles will actually be able to detect the disease site inside the body. That sounded very, very similar to the problem the farmers were actually facing — how do you get a medicine into a crop or a nutrient into a crop and get it to the right region within the crop where it’s actually necessary.”

The nanoparticles Schroeder developed are tiny packages that can deliver nutrients — any nutrients — that are placed inside.

A June 6, 2018 news item on Nanowerk offers a few more details,

An innovative technology developed at the Technion [Israel Institute of Technology] could lead to significant increases in agricultural yields. Using a nanometric transport platform on plants that was previously utilized for targeted drug delivery, researchers increased the penetration rate of nutrients into the plants, from 1% to approximately 33%.

A May 27,2018 Technion press release, which originated the news item, fleshes out the details,

The technology exploits nanoscale delivery platforms which until now were used to transport drugs to specific targets in the patient’s body. The work was published in Scientific Reports and will be presented in Nature Press.

The use of the nanotechnology for targeted drug delivery has been the focus of research activity conducted at the Laboratory for Targeted Drug Delivery and Personalized Medicine Technologies at the Wolfson Faculty of Chemical Engineering. The present research repurposes this technology for agricultural use; and is being pursued by laboratory director Prof. Avi Schroeder and graduate student Avishai Karny.

“The constant growth in the world population demands more efficient agricultural technologies, which will produce greater supplies of healthier foods and reduce environmental damage,” said Prof. Schroeder. “The present work provides a new means of delivering essential nutrients without harming the environment.”

The researchers loaded the nutrients into liposomes which are small spheres generated in the laboratory, comprised of a fatty outer layer enveloping the required nutrients. The particles are stable in the plant’s aqueous environment and can penetrate the cells. In addition, the Technion researchers can ‘program’ them to disintegrate and release the load at precisely the location and time of interest, namely, in the roots and leaves. Disintegration occurs in acidic environments or in response to an external signal, such as light waves or heat. The molecules comprising the particles are derived from soy plants and are therefore approved and safe for consumption by both humans and animals.

In the present experiment, the researchers used 100-nanometer liposomes to deliver the nutrients iron and magnesium into both young and adult tomato crops. They demonstrated that the liposomes, which were sprayed in the form of a solution onto the leaves, penetrated the leaves and reached other leaves and roots. Only when reaching the root cells did they disintegrate and release the nutrients. As said, the technology greatly increased the nutrient penetration rate.

In addition to demonstrating the effectivity of this approach as compared to the standard spray method, the researchers also assessed the regulatory limitations associated with the spread of volatile particles.

”Our engineered liposomes are only stable within a short spraying range of up to 2 meters,” explained Prof. Schroeder. “If they travel in the air beyond that distance, they break down into safe materials (phospholipids). We hope that the success of this study will expand the research and development of similar agricultural products, to increase the yield and quality of food crops.”

This is an illustration of the work,

Each liposome (light blue bubble) was loaded with iron and magnesium particles. The liposomes sprayed on the leaves, penetrated and then spread throughout the various parts of the plant and released their load within the cells. Courtesy: Technion

Here’s a link to and a citation for the paper,

Therapeutic nanoparticles penetrate leaves and deliver nutrients to agricultural crops by Avishai Karny, Assaf Zinger, Ashima Kajal, Janna Shainsky-Roitman, & Avi Schroeder. Scientific Reportsvolume 8, Article number: 7589 (2018) DOI: https://doi.org/10.1038/s41598-018-25197-y Published 17 May 2018

This paper is open access.

Agriculture and gene editing … shades of the AquAdvantage salmon

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Salmon are not the only food animals being genetically altered (more about that later in this post) we can now add cows, pigs, and more.

This November 15, 2018 article by Candice Choi on the Huffington Post website illustrates some of the excitement and terror associated with gene editing farm animals,

…

A company wants to alter farm animals by adding and subtracting genetic traits in a lab. It sounds like science fiction, but Recombinetics sees opportunity for its technology in the livestock industry.

But first, it needs to convince regulators that gene-edited animals are no different than conventionally bred ones. To make the technology appealing and to ease any fears that it may be creating Franken-animals, [emphasis mine] Recombinetics isn’t starting with productivity. Instead, it’s introducing gene-edited traits as a way to ease animal suffering.

“It’s a better story to tell,” said Tammy Lee, CEO of the St. Paul, Minnesota-based company.

For instance, animal welfare advocates have long criticized the way farmers use caustic paste or hot irons to dehorn dairy cows so the animals don’t harm each other. Recombinetics snips out the gene for growing horns so the procedure is unnecessary. [emphases mine]

Last year, a bull gene-edited by Recombinetics to have the dominant hornless trait sired several offspring. All were born hornless as expected, and are being raised at the University of California, Davis. Once the female offspring starts lactating, its milk will be tested for any abnormalities.

Another Recombinetics project: castration-free pigs.

When male piglets go through puberty, their meat can take on an unpleasant odour, something known as “boar taint.” To combat it, farmers castrate pigs, a procedure animal welfare advocates say is commonly performed without painkillers. Editing genes so that pigs never go through puberty would make castration unnecessary.

Also in development are dairy cows that could withstand higher temperatures, so the animals don’t suffer in hotter climates. [emphasis mine]

..

Before food from gene-edited animals can land on dinner tables, however, Recombinetics has to overcome any public unease about the technology.

Beyond worries about “playing God,” it may be an uncomfortable reminder of how modern food production already treats animals, said Paul Thompson, a professor of agriculture at Michigan State University.

“There’s an ethical question that’s been debated for at least the last 20 years, of whether you need to change the animal or change the system,” Thompson said.

Support for gene editing will also likely depend on how the technology is used: whether it’s for animal welfare, productivity or disease resistance. In August, a Pew study found 43 per cent of Americans supported genetically engineered animals for more nutritious meat.

…

Choi has written an interesting article, which includes a picture of the hornless cows embedded in the piece. One note: Choi makes reference to a milk glut. As far as I’m aware that’s not the case in Canada (at this time) but it is a problem in the US where in 2015 (?) farmers dumped some 43  million gallons of milk (October 12, 2016 article by Martha C. White for Money magazine).

As for the salmon, I’ve covered that story a few times during its journey to being approved for human consumption i Canada (my May 20, 2016 posting) to the discovery in 2017 that the genetically modified product, AquAdvantage salmon, had been introduced into the market, (from my Sept. 13, 2017 posting; scroll down about 40R of the way),

“Since the 2016 approval, AquAdvantage salmon, 4.5M tonnes has been sold in Canada according to an Aug. 8, 2017 article by Sima Shakeri for Huffington Post …”

After decades of trying to get approval by in North America, genetically modified Atlantic salmon has been sold to consumers in Canada.

AquaBounty Technologies, an American company that produces the Atlantic salmon, confirmed it had sold 4.5 tonnes of the modified fish on August 4 [2017], the Scientific American reported.

The fish have been engineered with a growth hormone gene from Chinook salmon to grow faster than regular salmon and require less food. They take about 18 months to reach market size, which is much quicker than the 30 months or so for conventional salmon.

The Washington Post wrote AquaBounty’s salmon also contains a gene from the ocean pout that makes the salmon produce the growth hormone gene all-year-round.

The company produces the eggs in a facility in P.E.I. [Prince Edward Island; a province in Canada], which is currently being expanded, and then they’re shipped to Panama where the fish are raised.

….

There was a bit of a kerfuffle about the whole affair but it seems Canadians have gone on to embrace the genetically modified product. At least that’s Christine Blank’s perspective in her Sept. 13, 2018 article (Canada, US embrace AquAdvantage GMO salmon, Brazil and China may be next) for the Genetic Literacy Project website,

Genetically modified salmon firm AquaBounty has found “very enthusiastic” buyers in Canada, according to president and CEO Ronald Stotish.

The first sale of the Maynard, Massachusetts, U.S.A.-based firm’s AquAdvantage salmon was made last June [2017], when unnamed buyers in Canada bought five metric tons at the going rate of traditional farmed Atlantic salmon, according to the company. Since then, AquaBounty has sold 10 additional metric tons of its AquAdvantage salmon to buyers in Canada

…

Meanwhile, Stotish revealed that AquAdvantage will be sold in the U.S. through established distributors.

“Once [AquaBounty salmon] is established in the market, the option for branding as a ‘sustainably produced’ food item can be considered,” he told investors.

…

Alex Gillis’ June 5, 2018 article for Macleans magazine suggests that Canadians may be a bit more doubtful about GM (genetically modified) salmon than Stotish seems to be believe,

…

An Ipsos Reid poll conducted for the Canadian Biotechnology Action Network in 2015 suggested that Canadians are concerned about GM foods, in spite of government assurances that they’re safe. About 60 per cent of respondents opposed genetically modifying crops and animals for food; nearly half supported a ban on all GM food. More than 20 years of surveys indicate that the vast majority of Canadians want to know when they’re eating GMOs. Fully 88 per cent of those polled in the 2015 survey said they want mandatory labelling.

Their concern hasn’t escaped the notice of those who raise and sell much of the salmon consumed in this country. Five years ago, Marine Harvest, one of the world’s largest producers of farmed salmon, called for labelling of GMOs. Today, it says that it doesn’t grow, sell or research GM salmon, a policy it shares with major salmon producers in Canada. And most big grocery retailers have stated they don’t want GM salmon. When contacted by Maclean’s for this story, Metro, Sobeys, Wal-Mart and Loblaws—four of Canada’s five largest food retailers—declared that none of AquaBounty’s GM salmon from 2017 was sold in their stores, saying neither Sea Delight Canada nor Montreal Fish Co. supplied them with Atlantic salmon at the time.

“I’m happy to report that we don’t source salmon from these two companies,” says Geneviève Grégoire, communications adviser with Metro Richelieu Inc., which operates or supplies 948 food stores in Quebec and Ontario, including Metro, Super C, Food Basics, Adonis and Première Moisson. “As we said before, we didn’t and will not sell GM Atlantic salmon.”

…

If you’re looking for a more comprehensive and critical examination of the issue, read Lucy Sharratt’s Sept. 1, 2018 article for the Canadian Centre for Policy Alternatives (CCPA).

Designer groundcherries by CRISPR (clustered regularly interspaced short palindromic repeats)

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I love the little things.. Groundcherries are just the right combination of sweet and tart.

Courtesy of Boyce Thompson Institute

They’re not in the stores very often and I wondered about that. Luckily, an  October 1, 2018 Boyce Thompson Institute news release by Mike Carroll (also on EurekAlert) explains why that is and how scientists are trying to overcome the difficulties,

You might not have heard of the groundcherry, or at least, never tasted one. But that could soon change thanks to research from the Van Eck Laboratory at Boyce Thompson Institute (BTI).

The groundcherry (Physalis pruinosa) is approximately the same size as a cherry tomato, but with a much sweeter flavor. The tropical-tasting fruit is also a powerhouse in terms of nutritional value. Packed with Vitamin C, Vitamin B, beta-carotene, phytosterols, and antioxidants, plus anti-inflammatory and medicinal properties, this tiny fruit might just be the next superfood.

“We feel there is potential for these to become a specialty fruit crop and to be grown on a larger scale in the US,” said Joyce Van Eck, associate professor at BTI.

However, even with their delicious flavor and nutritional value, groundcherries remain an underutilized crop in the United States. Several characteristics make them unsuitable for large-scale agriculture. [emphasis mine] In the October 1, 2018 issue of Nature Plants, Van Eck and colleagues present research which could change that and make groundcherries a common household name thanks to the genome editing tool CRISPR.

CRISPR has great promise for increasing crop productivity, especially for orphan crops such as groundcherries, which often contain undesirable characteristics resembling wild relatives. Leveraging knowledge from model crops (such as the tomato) can improve plant architecture (growth habit), flower production, fruit size, and more.

Selections for mutations in tomatoes have led to improvements in yield and Van Eck and her collaborator, Zach Lippman, at the Cold Spring Harbor Laboratory hypothesized that groundcherry genes could be similarly modified for immediate improvements. One concern with the groundcherry is its weedy growth habit. Genetic alterations have led to changes in the hormone that regulates flowering, producing plants which are more compact with fruit in clusters. They also targeted ways to increase fruit size and weight [emphases mine] through a CRISPR-generated mutation, leading to fifty-percent more fruit along a given stem and more seedy sections in each fruit.

“It’s exciting that we can take what we have learned in tomato and apply it to distantly related species,” said Van Eck.

Van Eck is also focused on fixing problems caused by fruit drop. [emphasis mine] Groundcherries drop to the ground, often before fully ripening.

This puts the fruit at risk for damage and creates a labor-intensive harvest process. In addition, fruit having to be gathered up from the ground causes concerns for food safety with potential for foodborne illness. A jointless mutation in tomatoes could provide the inspiration for using gene-editing to stop fruit drop in groundcherries.

“Physalis is the perfect candidate for looking at getting the fruit to not drop,” said Van Eck. “Gene editing might be the only way to fix this in the groundcherry.”

This study represents the first step towards improving the groundcherry and this work could be extended to target additional genes benefiting a range of consumer desirable traits.

Veronique Greenwood wrote an October 6, 2018 article for the New York Times about the scientists and the work featured in the October 1, 2018 issue of ‘Nature Plants’ and two scientists from Van Eck’s lab, Nathan T. Reem and Esperanza Shenstone, have written a November 14, 2018 essay about the work for The Conversation (h/t phys.org).

Here’s a link to and a citation for the research paper,

Rapid improvement of domestication traits in an orphan crop by genome editing by Zachary H. Lemmon, Nathan T. Reem, Justin Dalrymple, Sebastian Soyk, Kerry E. Swartwood, Daniel Rodriguez-Leal, Joyce Van Eck, & Zachary B. Lippman. Nature Plants volume 4, pages766–770 (2018) DOI: https://doi.org/10.1038/s41477-018-0259-x Published: 01 October 2018

This paper is behind a paywall.

All-natural agrochemicals

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Michael Berger in his May 4, 2018 Nanowerk Spotlight article highlights research into creating all natural agrochemicals,

Widespread use of synthetic agrochemicals in crop protection has led to serious concerns of environmental contamination and increased resistance in plant-based pathogenic microbes.

In an effort to develop bio-based and non-synthetic alternatives, nanobiotechnology researchers are looking to plants that possess natural antimicrobial properties.

Thymol, an essential oil component of thyme, is such a plant and known for its antimicrobial activity. However, it has low water solubility, which reduces its biological activity and limits its application through aqueous medium. In addition, thymol is physically and chemically unstable in the presence of oxygen, light and temperature, which drastically reduces its effectiveness.

…

Scientists in India have overcome these obstacles by preparing thymol nanoemulsions where thymol is converted into nanoscale droplets using a plant-based surfactant known as saponin (a glycoside of the Quillaja tree). Due to this encapsulation, thymol becomes physically and chemically stable in the aqueous medium (the emulsion remained stable for three months).

In their work, the researchers show that nanoscale thymol’s antibacterial and antifungal properties not only prevent plant disease but that it also enhances plant growth.

…

“It is exciting how nanoscale thymol is more active,” says Saharan [Dr. Vinod Saharan from the Nano Research Facility Lab, Department of Molecular Biology and Biotechnology, at Maharana Pratap University of Agriculture and Technology], who led this work in collaboration with Washington University in St. Louis and Haryana Agricultural University, Hisar. “We found that nanoscale droplets of thymol can easily pass through the surfaces of bacteria, fungi and plants and exhibit much faster and strong activity. In addition nanodroplets of thymol have a larger surface area, i.e. more molecules on the surface, so thymol becomes more active at the target sites.”

Here’s a link to and a citation for the paper,

Thymol nanoemulsion exhibits potential antibacterial activity against bacterial pustule disease and growth promotory effect on soybean by Sarita Kumari, R. V. Kumaraswamy, Ram Chandra Choudhary, S. S. Sharma, Ajay Pal, Ramesh Raliya, Pratim Biswas, & Vinod Saharan. Scientific Reportsvolume 8, Article number: 6650 (2018) doi:10.1038/s41598-018-24871-5 Published: 27 April 2018

This paper is open access.

Final note

There is a Canadian company which specialises in nanoscale products for the agricultural sector, Vive Crop Protection. I don’t believe they claim their products are ‘green’ but due to the smaller quantities needed of Vive Crop Protection’s products, the environmental impact is less than that of traditional agrochemicals.

Genetic engineering: an eggplant in Bangladesh and a synthetic biology grant at Concordia University (Canada)

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I have two bits of genetic engineering news.

Eggplants in Bangladesh

I always marvel at their beauty,

Bt eggplant is the first genetically engineered food crop to be successfully introduced in South Asia. The crop is helping some of the world’s poorest farmers feed their families and communities while reducing the use of pesticides. Photo by Cornell Alliance for Science.

A July 17, 2018 news item on phys.org describes a genetic engineering application,

Ansar Ali earned just 11,000 taka – about $130 U.S. dollars – from eggplant he grew last year in Bangladesh. This year, after planting Bt eggplant, he brought home more than double that amount, 27,000 taka. It’s a life-changing improvement for a subsistence farmer like Ali.

Bt eggplant, or brinjal as it’s known in Bangladesh, is the first genetically engineered food crop to be successfully introduced in South Asia. Bt brinjal is helping some of the world’s poorest farmers to feed their families and communities, improve profits and dramatically reduce pesticide use. That’s according to Tony Shelton, Cornell professor of entomology and director of the Bt brinjal project funded by the United States Agency for International Development (USAID). Shelton and Jahangir Hossain, the country coordinator for the project in Bangladesh, lead the Cornell initiative to get these seeds into the hands of the small-scale, resource-poor farmers who grow a crop consumed daily by millions of Bangladeshis.

A July 11, 2018 Cornell University news release by Krisy Gashler, which originated the news item, expands on the theme (Note: Links have been removed),

Bt brinjal was first developed by the Indian seed company Mahyco in the early 2000s. Scientists inserted a gene from the bacterium Bacillus thuringiensis (thus the name, Bt) into nine brinjal varieties. The plants were engineered to resist the fruit and shoot borer, a devastating insect whose larvae bore into the stem and fruit of an eggplant. The insects cause up to 80 percent crop loss.

The Bt protein produced by the engineered eggplant causes the fruit and shoot borer larva to stop feeding, but is safe for humans consuming the eggplant, as proven through years of biosafety trials. In fact, Bt is commonly used by organic farmers to control caterpillars but has to be sprayed frequently to be effective. The Bt eggplant produces essentially the same protein as in the spray. More than 80 percent of field corn and cotton grown in the U.S. contains a Bt gene for insect control.

“Farmers growing Bt brinjal in Bangladesh are seeing three times the production of other brinjal varieties, at half the production cost, and are getting better prices at the market,” Hossain said.

A recent survey found 50 percent of farmers in Bangladesh said that they experienced illness due to the intense spraying of insecticides. Most farmers work in bare feet and without eye protection, leading to pesticide exposure that causes skin and eye irritation, and vomiting.

“It’s terrible for these farmers’ health and the health of the environment to spray so much,” said Shelton, who found that pesticide use on Bt eggplant was reduced as much as 92 percent in commercial Bt brinjal plantings. “Bt brinjal is a solution that’s really making a difference in people’s lives.”

Alhaz Uddin, a farmer in the Tangail district, made 6,000 taka growing traditional brinjal, but had to spend 4,000 taka on pesticides to combat fruit and shoot borer.

“I sprayed pesticides several times in a week,” he said. “I got sick many times during the spray.”

Mahyco initially wanted to introduce Bt brinjal in India and underwent years of successful safety testing. But in 2010, due to pressure from anti-biotechnology groups, the Indian minister of the environment placed a moratorium on the seeds. It is still in effect today, leaving brinjal farmers there without the effective and safe method of control available to their neighbors in Bangladesh.

Even before the Indian moratorium, Cornell scientists hosted delegations from Bangladesh that wanted to learn about Bt brinjal and the Agricultural Biotechnology Support Project II (ABSP II), a consortium of public and private institutions in Asia and Africa intended to help with the commercial development, regulatory approval and dissemination of bio-engineered crops, including Bt brinjal.

Cornell worked with USAID, Mahyco and the Bangladesh Agricultural Research Institute to secure regulatory approval, and in 2014 the Bangladeshi government distributed a small number of Bt brinjal plants to 20 farmers in four districts. The next year 108 farmers grew Bt brinjal, and the following year the number of farmers more than doubled to 250. In 2017 the number increased to 6,512 and in 2018 to 27,012. The numbers are likely even higher, according to Shelton, as there are no constraints against farmers saving seeds and replanting.

“Farmers who plant Bt brinjal are required to plant a small perimeter of traditional brinjal around the Bt variety; research has shown that the insects will infest plants in the buffer area, and this will slow their evolutionary development of resistance to the Bt plants,” Shelton said.

In a March 2017 workshop, Bangladeshi Agriculture Minister Begum Matia Chowdhury called Bt brinjal “a success story of local and foreign collaboration.”

“We will be guided by the science-based information, not by the nonscientific whispering of a section of people,” Chowdhury said. “As human beings, it is our moral obligation that all people in our country should get food and not go to bed on an empty stomach. Biotechnology can play an important role in this effect.”

Here’s what an infested eggplant looks like,

Non-Bt eggplant infested with fruit and shoot borer. Photo by Cornell Alliance for Science

It looks more like a fig than an eggplant.

This is part of a more comprehensive project as revealed in a March 29, 2016 Cornell University news release issued on the occasion of a $4.8M, three-year grant from the U.S. Agency for International Development (USAID),

… The award supports USAID’s work under Feed the Future, the U.S. government’s global initiative to fight hunger and improve food security using agricultural science and technology.

In the Feed the Future South Asia Eggplant Improvement Partnership, Cornell will protect eggplant farmers from yield losses and improve their livelihoods in partnership with the Bangladesh Agricultural Research Institute (BARI) and the University of the Philippines at Los Baños. Eggplant, or brinjal, is a staple crop that is an important source of income and nutrition for farmers and consumers in South Asia.

…

Over the past decade, Cornell has led the Agricultural Biotechnology Support Project II (ABSPII), also funded by USAID, that prompted a consortium of institutions in Asia and Africa to use the tools of modern biotechnology, particularly genetic engineering, to improve crops to address major production constraints for which conventional plant breeding tools have not been effective.

…

In October 2013, Bangladesh became the first country in South Asia to approve commercial cultivation of a genetically engineered food crop. In February 2014, Matia Chowdhury, the Bangladesh minister of agriculture, released four varieties of Bt brinjal to 20 farmers. With the establishment of the 20 Bt brinjal demonstration plots in 2014 and 104 more in 2015, BARI reported a noticeable decrease in fruit and shoot borer infestation, increased yields, decreased use of pesticide and improved income for farmers.

…

The Feed the Future South Asia Eggplant Improvement Partnership addresses and integrates all elements of the commercialization process — including technology development, regulation, marketing, seed distribution, and product stewardship. It also provides strong platforms for policy development, capacity building, gender equality, outreach and communication.

Moving on from practical applications …

Canada’s synthetic biology training centre

It seems Concordia University (Montréa) is a major Canadian centre for all things ‘synthetic biological’. (from the History and Vision webpage on Concordia University’s Centre for Applied Synthetic Biology webspace),

History and vision

Emerging in 2012 from a collaboration between the Biology and Electrical and Computer Engineering Departments, the Centre received University-wide status in 2016 growing its membership to include Biochemistry, Journalism, Communication Studies, Mechanical, Industrial and Chemical Engineering.

Timeline

T17-36393-VPRG-Timeline-graphic-promo-v4

You can see the timeline does not yet include 2018 development(s). Also it started as “a collaboration between the Biology and Electrical and Computer Engineering Departments?” This suggests a vastly different approach to genetic engineering that that employed in the “eggplant” research. From a July 16, 2018 posting on the Genome Alberta blog,

The Natural Sciences and Engineering Research Council of Canada (NSERC) has committed $1.65 million dollars over six years to establish a research and training program at Concordia’s Centre for Applied Synthetic Biology.

The funds were awarded after Malcolm Whiteway (…), professor of biology and the Canada Research Chair in Microbial Genomics, and the grant application team submitted a proposal to NSERC’s Collaborative Research and Training Experience (CREATE) program.

The Synthetic Biology Applications CREATE program — or SynBioApps — will help students acquire and develop important professional skills that complement their academic education and improve their job-readiness.

‘Concordia is a natural fit’

“As the Canadian leader in synthetic biology and as the home of the country’s only genome foundry, Concordia is a natural fit for a training program in this growing area of research,” says Christophe Guy, vice-president of Research and Graduate Studies.

“In offering a program like SynBioApps, we are providing our students with both a fundamental education in science and the business skills they’ll need to transition into their professional careers.”

The program’s aims are twofold: First, it will teach students how to design and construct cells and proteins for the development of new products related to human health, green technologies, and fundamental biological investigations. Second, it will provide cross-disciplinary training and internship opportunities through the university’s District 3 Innovation Center.

SynBioApps will be open to students from biology, biochemistry, engineering, computing, and mathematics.

“The ability to apply engineering approaches to biological systems promises to revolutionize both biology and industry,” says Whiteway, who is also a member of the Centre for Applied Synthetic Biology.

“The SynBioApps program at Concordia will provide a training program to develop the students who will both investigate the biology and build these industries.”

…

You can find out more about Concordia’s Centre for Applied Synthetic Biology here (there are jobs listed on their home page) and you can find information about the Synthetic Biology Applications (SynBioApps) training programme here.

Carbon nanotubes for enhanced wheat growth?

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It’s been a long time (Oct. 22, 2009 posting; scroll down about 20% of the way) since I’ve written about carbon nanotubes and their possible use in agriculture but now a December 6, 2017 news item on ScienceDaily raises the topic again,

The introduction of purified carbon nanotubes appears to have a beneficial effect on the early growth of wheatgrass, according to Rice University scientists. But in the presence of contaminants, those same nanotubes could do great harm.

The Rice lab of chemist Andrew Barron grew wheatgrass in a hydroponic garden to test the potential toxicity of nanoparticles on the plant. To their surprise, they found one type of particle dispersed in water helped the plant grow bigger and faster.

They suspect the results spring from nanotubes’ natural hydrophobic (water-avoiding) nature that in one experiment apparently facilitated the plants’ enhanced uptake of water.

The research appears in the Royal Society of Chemistry journal Environmental Science: Nano.

A December 6, 2017 Rice University news release (also on EurekAlert), which originated the news item, expands on the theme,

The lab mounted the small-scale study with the knowledge that the industrial production of nanotubes will inevitably lead to their wider dispersal in the environment. The study cited rapid growth in the market for nanoparticles in drugs, cosmetic, fabrics, water filters and military weapons, with thousands of tons produced annually.

Despite their widespread use, Barron said few researchers have looked at the impact of environmental nanoparticles — whether natural or man-made — on plant growth.

The researchers planted wheatgrass seeds in multiple replicates in cotton wool and fed them with dispersions that contained raw single-walled or multi-walled nanotubes, purified single-walled nanotubes or iron oxide nanoparticles that mimicked leftover catalyst often attached to nanotubes. The solutions were either water or tetrahydrofuran (THF), an industrial solvent. Some of the seeds were fed pure water or THF as a control.

Rice University researchers tested the effects of carbon nanotubes on the growth of wheatgrass. While some showed no effect, purified single-walled nanotubes in water (5) enhanced the plants' growth, while the same nanotubes in a solvent (6) retarded their development. The photos at left show the plants after four days and at right after eight days, with odd-numbered plants growing in water and evens in a solvent. Numbers 1 and 2 are controls without nanotubes; 3-4 contain raw single-walled tubes; 5-6 purified single-walled tubes; 7-8 raw multi-walled tubes; 9-10 low-concentration iron-oxide nanoparticles and 11-12 high-concentration iron-oxide nanoparticles.

Rice University researchers tested the effects of carbon nanotubes on the growth of wheatgrass. While some showed no effect, purified single-walled nanotubes in water (5) enhanced the plants’ growth, while the same nanotubes in a solvent (6) retarded their development. The photos at left show the plants after four days and at right after eight days, with odd-numbered plants growing in water and evens in a solvent. Numbers 1 and 2 are controls without nanotubes; 3-4 contain raw single-walled tubes; 5-6 purified single-walled tubes; 7-8 raw multi-walled tubes; 9-10 low-concentration iron-oxide nanoparticles and 11-12 high-concentration iron-oxide nanoparticles. Click on the image for a larger version. Photos by Seung Mook Lee

After eight days, the plantings showed that purified single-walled nanotubes in water enhanced the germination rate and shoot growth of wheatgrass, which grew an average of 13 percent larger than plants in plain water. Raw single- and multi-walled nanotubes and particles in either solution had little effect on the plants’ growth, they found.

However, purified single-walled nanotubes in THF retarded plant development by 45 percent compared to single-walled nanotubes in water, suggesting the nanotubes act as a carrier for the toxic substance.

The concern, Barron said, is that if single-walled nanotubes combine with organic pollutants like pesticides, industrial chemicals or solvents in the environment, they may concentrate and immobilize the toxins and enhance their uptake by plants.

Nothing seen in the limited study indicated whether carbon nanotubes in the environment, and potentially in plants, will rise up the food chain and be harmful to humans, he said.

On the other hand, the researchers said it may be worth looking at whether hydrophobic substrates that mimic the positive effects observed in single-walled nanotubes could be used for high-efficiency channeling of water to seeds.

“Our work confirms the importance of thinking of nanomaterials as part of a system rather in isolation,” Barron said. “It is the combination with other compounds that is important to understand.”

Seung Mook Lee, a former visiting student research assistant from Memorial High School in Houston and now an undergraduate student at the University of California, Berkeley, is lead author of the paper. Co-authors are Rice research scientist Pavan Raja and graduate student Gibran Esquenazi. Barron is the Charles W. Duncan Jr.–Welch Professor of Chemistry and a professor of materials science and nanoengineering at Rice and the Sêr Cymru Chair of Low Carbon Energy and Environment at Swansea University, Wales (UK).

The Welsh Government Sêr Cymru Program and the Robert A. Welch Foundation supported the research.

Here’s a link to and a citation for the paper,

Effect of raw and purified carbon nanotubes and iron oxide nanoparticles on the growth of wheatgrass prepared from the cotyledons of common wheat (triticum aestivum) by Seung Mook Lee, Pavan M. V. Raja, Gibran L. Esquenazi, and Andrew R. Barron. Environ. Sci.: Nano, 2018, Advance Article DOI: 10.1039/C7EN00680B First published on 09 Nov 2017

This paper appears to be behind a paywall.