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Archive for the ‘RNA’ Category

ucr-today

Researchers develop strategy that could lead to environmentally friendly fungicide to fight pathogens that cause billions of dollars in crop loss

gray mold on fruit, vegetables and flowersThe images third from the bottom and at the bottom show fruit, vegetables and flowers treated with pathogen gene-targeting RNA molecules. The other images represent various control methods.

 

RIVERSIDE, Calif. (www.ucr.edu) — Have you ever bought strawberries or other fruits and vegetables, forgot to put them in the refrigerator and later noticed they had gray mold on some of them?

That’s Botrytis cinerea, a fungal pathogen that can infect more than 1,000 plant species, including almost every fruit and vegetable and many flowers. Wine grapes are also a notable host – in grapes the condition is known as bunch rot. It causes billions of dollars in crop loss annually.

A team of researchers, led by Hailing Jin, a University of California, Riverside professor of plant pathology and microbiology, have developed a new strategy that could provide an easy-to-use and environmentally friendly fungicide to fight B. cinerea and other fungal pathogens that harm crops.

The findings were just published in the journal Nature Plants.

These findings build on a paper by Jin’s group published in 2013 in the journal Science. In that paper, they outlined how they discovered the mechanism by which B. cinerea infects plants.

Many pathogens secrete protein effectors molecules to manipulate and – eventually – compromise host immunity. The researchers, led by Jin, found three years ago for the first time that B. cinerea can deliver small RNA effector molecules to the host cells to induce cross-kingdom RNA interference (RNAi) to suppress host immunity.

Building on that work, in the just-published study in Nature Plants, they discovered that such cross-kingdom RNAi is bidirectional, meaning small RNAs can flow from the pathogen to the host and from the host to the pathogen.

Furthermore, they found that B. cinerea is capable of taking up RNA molecules from the environment, which makes it possible to use such external RNAs in fungicidal sprays to manage diseases.

The researchers tested that idea and found that applying those pathogen gene-targeting RNA molecules to the surface of fruits and vegetables and flowers – they used tomato, strawberry, grape, lettuce, onion, and rose – can control gray mold diseases.

The findings outlined in the Science and Nature Plants papers have significant implications for farmers looking to control fungal pathogens. Currently, fungicides and chemical spraying are still the most common disease control strategy. But, these treatments pose serious threats to human health and environments. RNA, which is present in all living organisms, doesn’t present problems for human health and it naturally degrades in soil.

While the research focused on the fungal pathogens B. cinerea and Verticillium dahliae, another fungal pathogen that causes wild disease on dozens of trees, shrubs, vegetables, and fields crops, the researchers believe this RNAi-based technique could be used to control multiple pathogens at the same time.

While the research focused on the fungal pathogen B. cinerea, the researchers believe the technique could be used to control other fungal pathogens, such as Verticllium dahliae, which causes wild disease on dozens of trees, shrubs, vegetables, and fields crops.

It also has the potential to decrease the use of GMOs by providing an effective, environmentally friendly way to control plant diseases.

The Nature Plants paper is called “Bidirectional cross-kingdom RNAi and fungal uptake of external RNAs confer plant protection.” In addition to Jin, the authors are Ming Wang and Arne Weiberg, both of UC Riverside; Arne Weiberg, who recently got a faculty position at the University of Munich; Feng-Mao Lin and Hsien-Da Huang, both of National Chiao Tung University in China; and Bart P. H. J. Thomma of Wageningen University in the Netherlands.

This research was supported by grants Jin received from the National Science Foundation and National Institutes of Health.

The invention has a patent pending status.

 

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DukeToday

planthopper_SmallOne of the leading pests of rice, brown planthoppers can grow up to have either short or long wings, depending on conditions such as day length and temperature in the rice fields where they suck sap. The hormone insulin controls the switch that tells young planthoppers whether to develop into short- or long-winged adults, finds a new study. Photo by Chuan-Xi Zhang of Zhejiang University in China

Insulin tells young planthoppers whether to develop short or long wings

DURHAM, NC – Each year, rice in Asia faces a big threat from a sesame seed-sized insect called the brown planthopper, Nilaparvata lugens. Now, a study reveals the molecular switch that enables some planthoppers to develop short wings and others long — a major factor in their ability to invade new rice fields.

Lodged in the stalks of rice plants, planthoppers use their sucking mouthparts to siphon sap. Eventually the plants turn yellow and dry up, a condition called “hopper burn.”

Each year, planthopper outbreaks destroy hundreds of thousands of acres of rice, the staple crop for roughly half the world’s population.

The insects have a developmental strategy that makes them particularly effective pests. When conditions in a rice field are good, young planthoppers develop into adults with stubby wings that barely reach their middles.

Short-winged adults can’t fly but they’re prolific breeders. A single short-winged female can lay more than 700 eggs in her lifetime.

“The short-winged ones have great big fat abdomens. They’re basically designed to stay put and reproduce,” said biologist Fred Nijhout of Duke University, who co-authored the study with colleagues at Zhejiang University in China.

But in the fall as days get shorter and temperatures begin to drop — signs that the rice plants they’re munching on will soon disappear — more planthopper nymphs develop into slender adults with long wings. Long-winged planthoppers lay fewer eggs but are built for travel, eventually flying away to invade new rice fields.

Until now, scientists did not know exactly how the shorter days and cooler temperatures triggered the shift between short and long wings, or which hormones were involved.

To find out, the researchers used a technique called RNA interference (RNAi) to silence the genes for two different insulin receptors — regions on the cell membrane that bind to the hormone insulin — and measured the effects on the animals’ wings.

“Previously it had been assumed that all insects only had a single insulin receptor gene. We discovered that brown planthoppers have two,” Nijhout said.

When the researchers silenced the first insulin receptor, short-winged adults emerged. Silencing the second receptor produced adults with long wings.

Further study revealed that long wings are the default design. But when planthoppers secrete a particular type of insulin in response to changing temperatures or day length, the second insulin receptor deactivates the first receptor in the developing wings, leading to short-winged adults.

“The second insulin receptor acts by interfering with the first one, therefore shutting down the signal,” Nijhout said.

It’s too early to say whether the findings could lead to techniques to treat planthopper populations so they are unable to invade new rice fields, Nijhout says.

But the researchers have found similar mechanisms in other planthopper species, and are now trying to find out if insulin plays a similar role in other insect pests with flying and flightless forms, such as aphids.

This research was supported by the National Basic Research Program of China (973 Program, no. 2010CB126205) and by the National Science Foundation of China (no. 31201509 and no. 31471765).

https://today.duke.edu/2015/03/planthoppers

The appeared Mar. 18 in the journal Nature.

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Colo pot beetle rnaiThe Colorado potato beetle, also known as an international super pest, munches on a potato plant leaf.
Credit: MPI for Molecular Plant Physiology and MPI for Chemical Ecology

 

Insecticides: Researchers stop the Colorado potato beetle in its tracks by preventing the insect from synthesizing essential proteins
By Sarah Everts
Department: Science & Technology
News Channels: Biological SCENE, Environmental SCENE

 

The Colorado potato beetle, also known as an international super pest, munches on a potato plant leaf.
Credit: MPI for Molecular Plant Physiology and MPI for Chemical Ecology
The Colorado potato beetle costs the agricultural industry billions of dollars per year and devours so many crops around the world that the insect has been branded an “international super pest.” Because the pest has become resistant to all major classes of insecticides and has few natural enemies, crop scientists are seeking a strategy to rein in the beetle’s feeding frenzies.
A team of researchers led by Ralph Bock at the Max Planck Institute for Molecular Plant Physiology, in Potsdam, Germany, now reports that it has found a way to protect crops from the Colorado potato beetle with a new insecticidal tool: RNA interference, or RNAi (Science 2015, DOI: 10.1126/science.1261680).
To use RNAi against the pest, the researchers first identified a gene the insect can’t do without—one that encodes a cytoskeleton protein vital to maintaining a cell’s shape. Researchers then engineered vulnerable plants to produce a custom double-stranded RNA. As the insect pest dines on the plant, the double-stranded RNA gets converted into small interfering RNA. These fragments prevent the insect’s ribosome from reading the messenger RNA for the essential protein. The obstruction blocks production of the essential protein, and the insect dies.
The inspiration to use RNAi to kill pests dates back nearly a decade, says Jiang Zhang, the study’s first author.
Although the RNAi strategy was implemented in plants years ago, it failed as a powerful insecticide because the pests didn’t all die, explains Steve Whyard, at the University of Manitoba, in Winnipeg, in an associated commentary (Science 2015, DOI: 10.1126/science.aaa7722). Bock, Zhang, and their colleagues, however, have now made a “clever modification” to the earlier, partially successful strategy, Whyard notes, by inserting the instructions to make the double-stranded insecticidal RNA into plant cells’ chloroplasts, instead of into their nuclei. The result of putting the insecticidal RNA into chloroplasts, a plant’s photosynthesis hot spot, was full crop protection from the Colorado potato beetle.
Previous attempts probably didn’t work well because the cytoplasm within plant cells has machinery that metabolizes double-stranded RNA before pests such as the Colorado potato beetle can consume it. Conversely, chloroplasts have no machinery to metabolize double-stranded RNA, allowing the insecticidal molecules to accumulate and be stored until a pest dines on the plant.
One general benefit of the RNAi approach, Zhang says, is that researchers can selectively target specific insect pests by targeting species-specific gene sequences; this avoids the blanket destruction of other insect species seen with many insecticides, he explains.
Whether the new approach will work on other insect pests is an open question, comments Niels Wynant, who studies pest control at KU Leuven, in Belgium. And it remains to be seen how quickly pests will develop resistance mechanisms to the RNAi insecticides. That being said, Wynant adds, the findings could have a “significant impact” on pest control strategies and should be further investigated by agricultural companies.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2015 American Chemical Society

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Wheat streak mosaic KSU(1)

Wheat streak mosaic virus is one of the most damaging and costly diseases wheat producers encounter, but plant pathologists have recently uncovered a way for the wheat plant to defend itself against this particular virus and others.

 

Helping Wheat Defend Itself Against Damaging Viruses

Patent-pending technology has shown success in disease resistance to wheat streak mosaic virus and triticum mosaic virus, among others.

Released: 18-Nov-2014 10:30 AM EST
Source Newsroom: Kansas State University Research and Extension

Newswise — MANHATTAN, Kan. – Wheat diseases caused by a host of viruses that might include wheat streak mosaic, triticum mosaic, soil-borne mosaic and barley yellow dwarf could cost producers 5 to 10 percent or more in yield reductions per crop, but a major advance in developing broad disease-resistant wheat is on the horizon.
John Fellers, molecular biologist for the U.S. Department of Agriculture’s Agricultural Research Service, and Harold Trick, plant geneticist for Kansas State University, have led an effort to develop a patent-pending genetic engineering technology that builds resistance to certain viruses in the wheat plant itself. And although genetically engineered wheat is not an option in the market today, their research is building this resistance in non-genetically engineered wheat lines as well.
“(Wheat viruses) are a serious problem,” Trick said. “Wheat streak mosaic virus is one of the most devastating viruses we have. It’s prevalent this year. In addition to that, we have several other diseases, triticum mosaic virus and soil-borne mosaic virus, that are serious diseases.”
Knowing how costly these diseases can be for producers, Fellers has worked on finding solutions for resistance throughout his career. As a doctoral student at the University of Kentucky, he used a technology in his research called pathogen-derived resistance, or RNA-mediated resistance—a process that requires putting a piece of a virus into a plant to make it resistant to that particular virus. Most of the viruses that infect wheat are RNA viruses, he said.
“The plant has its own biological defense system,” Fellers said. “We were just triggering that with this technology.”
Now Fellers, with the help of Trick, his wheat transformation facility and K-State graduate students, have developed transgenic wheat lines that contain small pieces of wheat streak mosaic virus and triticum mosaic virus RNA.
“It’s kind of like forming a hairpin of RNA,” Fellers said. “What happens is the plant recognizes this RNA isn’t right, so it clips a piece of it and chops it up, but then it keeps a copy for itself. Then we have a resistance element.”
Fellers compared the process to the old days of viewing most wanted posters on the post office wall. The piece of foreign RNA from the virus, which is a parasite, is one of those most wanted posters. Because the virus is a parasite, it has to seize or hijack part of the plant system to make proteins that it needs to replicate.
When the virus comes into the plant, the plant holds up that poster from the post office wall, recognizes the virus, and doesn’t allow the virus to replicate and go through its lifecycle.
A broad resistance goal
Trick said it wasn’t difficult to incorporate the RNA into the wheat, as it involved a standard transformation process where the DNA encoding the RNA was introduced into plant cells, plants were regenerated from these transformed cells, and then the transgenic plants underwent testing for disease resistance.
“The problem with this technology is the most wanted poster is only for one individual,” Trick added. “If we were trying to target multiple genes, we’d have to make another vector for a second virus, then create that transgenic, which we have done. So, we have different plants that are genetically resistant to wheat streak mosaic virus and plants that are resistant to triticum mosaic virus. We would like to get something that has broad resistance to many different viruses.”
Knowing again that the viruses are parasites that rely on part of the plant system to replicate, it may be possible to shut off these plant systems to prevent viral replication, Trick said, which in essence means making a most wanted poster for specific plant genes.
Fellers and Trick have made additional transgenic plants with a most wanted poster for these plant genes and tested their new plants for resistance to a number of wheat viruses.
“We’re now able to target barley yellow dwarf and soil-borne mosaic viruses,” Fellers said. “We’ve also done mixed infection tests with wheat streak mosaic and triticum mosaic (viruses), and our initial results now are that they’re all resistant. We’re very cautious, but our initial indications show we have come up with something that provides broad resistance to these four viruses. We thought it was important enough to file for a patent.”
Fellers said this work is a proof of concept, meaning it shows that researchers have an ability now to address these virus issues. The fact that the process uses genetic engineering would mean that getting broad-resistance wheat would take some time considering the public and industry would have to accept it first.
However, Trick said they are now pursuing a non-genetically engineered method that involves turning off specific plant genes using mutations. With this method, the researchers could develop the technology and incorporate it into the K-State breeding program without regulations.
“We would hope the turn around time would be quick, but it’s still classical breeding,” Fellers said of using mutations. “It’s a matter of developing markers and getting them in the varieties. We have been using Jagger and Karl 92, varieties that are already past their prime, so we have to get them in some newer varieties.”
The Kansas Wheat Commission has provided funding for this research. More information about K-State’s Department of Plant Pathology is available online (http://www.plantpath.ksu.edu). A video interview with Fellers and Trick can be found on the K-State Research and Extension YouTube page (http://youtu.be/mXiw78MpS0E).

 

 

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Phys.Org

Aug 22,2014

http://phys.org/news/2014-08-virus-dna.html

dnaplantscanswi

A team of virologists and plant geneticists at Wageningen UR has demonstrated that when tomato plants contain Ty-1 resistance to the important Tomato yellow leaf curl virus (TYLCV), parts of the virus DNA (the genome) become hyper-methylated, the result being that virus replication and transcription is inhibited. The team has also shown that this resistance has its Achilles heel: if a plant is simultaneously infected with another important (RNA) virus, the Cucumber mosaic virus (CMV), the resistance mechanism is compromised.

Antiviral defence via RNAi
Plant defence to viruses usually depends on RNA interference (RNAi). The genetic material of many viruses consists of RNA. A complex process in the plant causes the virus RNA to be chopped up into pieces, which means the virus can no longer multiply. In contrast to most other disease-causing plant viruses, the genetic material in TYLCV is DNA, not RNA. Therefore antiviral RNAi defence to these viruses has to happen somewhat different.

TYLCV is one of the most economically important plant viruses in the world; for this virus a number of resistance genes (Ty-1 to Ty-6) are available to commercial plant breeders. In 2013 the researchers in Wageningen succeeded in identifying and cloning the Ty-1 gene, which happened to present a member from an important class of RNAi-pathway genes. This led to a publication in PLoS Genetics. Their recent publication in the journal PNAS shows that although Ty-1 resistance depends on RNAi, instead of the genetic material being chopped up, it is being ‘blocked’ by methylation of the virus DNA.

No cross protection
A well-known phenomenon in the plant world is the ‘immunisation’ of plants by infecting them with relatively harmless viruses. The latter ensures that the defence mechanisms in plants are activated and provide ‘cross protection’ against more harmful, related viruses.

To their great surprise, the Wageningen researchers discovered that infection with CMV, a virus that contains RNA as genetic material and that, as a result, is not affected by the Ty-1 resistance mechanism, actually compromised resistance to the TYLCV virus. According to the researchers, this is a warning to plant breeders. The use of the Ty-1 gene does provide resistance, but the mechanism will be at risk in plants grown in greenhouses and fields if the plants are attacked by various other types of viruses.

Explore further: Virus rounds up enzymes, disarms plant
More information: Patrick Butterbach, Maarten G. Verlaan, Annette Dullemans, Dick Lohuis, Richard G. F. Visser, Yuling Bai, and Richard Kormelink. “Tomato yellow leaf curl virus resistance by Ty-1 involves increased cytosine methylation of viral genomes and is compromised by cucumber mosaic virus infection.” PNAS 2014 ; published ahead of print August 18, 2014, DOI: 10.1073/pnas.1400894111
Journal reference: PLoS Genetics Proceedings of the National Academy of Sciences
Provided by Wageningen University

Read more at: http://phys.org/news/2014-08-virus-dna.html#jCp

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