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Inner Mongolia Agricultural University in China: Novel strategies for antiviral resistance in potatoes.

Posted in Biotechnology, CRISPR, GMOs, Host plant resistance, RNA, Viruses on June 1, 2023| Leave a Comment »

Across Regions, All latest News, News May 2023, Pests and Diseases, Research, Studies/Reports

The battle against viral diseases: Novel strategies for antiviral resistance in potatoes

on May 17, 2023

This article was written by Jorge Luis Alonso G., an information consultant specializing
in the potato crop.

Scientists at the Inner Mongolia Agricultural University in China recently published a review in the journal Plants describing the advancement of antiviral strategies in potatoes through the engineering of both viral and plant-derived genes.

The article below is a summary of the information presented in this scientific paper.

1. Introduction

Potatoes, as a nutritious and staple food crop, have the potential to address food insecurity in developing countries. However, a major impediment to this aptitude is the prevalence of viral diseases in potato production, which result in the destruction of seed potatoes and often cause yield losses of 20–30%. Major viruses, including Potato virus Y (PVY), Potato leafroll virus (PLRV), and Potato virus X (PVX), cause various damaging symptoms such as leaf curling, necrosis, and stunted growth.

Complicating disease prevention, these viruses enter the plant through various vectors and use plant resources to replicate. Although virus-free seed potato technology can limit disease damage, some viruses are persistent and can re-infect during the growing season.

In addition, the hetero-tetraploid nature of the plant limits conventional breeding methods in developing antiviral potato varieties. On the positive side, advances in molecular biology and plant genetic engineering have opened the door to creating virus-resistant crops. Promising strategies have emerged, such as RNA interference (RNAi)-mediated resistance, which targets the viral coat proteins of the major potato viruses.

Eventually, genetically modified (GM) potatoes, including virus-resistant varieties, are now being introduced and commercialized in certain countries. This progress represents a major step forward in the fight against potato virus diseases.

2. Engineering Virus-Derived Viral Resistance in Potato

Researchers have developed genetically engineered virus-resistant plants, including potatoes, by using the coat protein (CP) gene of viruses such as tobacco mosaic virus (TMV), PVY, PVX, and PLRV. CP has several functions, including protection of the viral nucleic acid and regulation of the host range of infection. However, CP-mediated resistance is often limited, providing protection only against the CP donor virus or related strains and only at low viral doses. Additional complications in virus transmission can arise when the plant is transformed with the CP of an insect-borne virus.

To overcome these challenges, investigators are attempting to combine different viral CPs in the same plant or to incorporate coat protein genes with satellite RNA for a broader antiviral spectrum. An alternative approach involves replicase, an RNA polymerase encoded by viral genes. This enzyme synthesizes the positive and negative strands of viral RNA during replication. Although researchers have shown that replicase-mediated resistance is stronger than CP-mediated resistance, its specificity limits its use in the field due to the rapid mutation rate of plant RNA viruses.

In addition, antisense RNAs (asRNAs), which are complementary to messenger RNA (mRNA), have also been used for viral resistance. Although some success has been achieved in acquiring antiviral infection ability and protecting plants, antisense RNA-directed resistance is generally weak due to insufficient expression, which limits its practical application. However, there are still ways to improve the expression level of antisense RNA, which keeps this avenue open for exploration.

3. Engineering Virus-Resistant Plants Using Plant Endogenous Genes in Potato

Scientists are increasingly focusing on creating virus-resistant plants by using the plant’s own genes. They have discovered antiviral genes in both wild and cultivated potato species. These can be categorized into two distinct groups: extreme resistance (ER) genes and hypersensitive resistance (HR) genes. ER genes are known to resist many viruses and thwart viral reproduction in the early stages of infection. On the other hand, HR genes resist various virus species, triggering cell necrosis after a virus infection to limit its spread.

In potatoes, the Ry genes confer ER to all PVY strains, including the Rysto, Ryadg, and Rychc genes. Breeders have incorporated these into potato breeding programs and have identified Rysto as recognizing the central 149 amino acids of the PVY coat protein domain, suggesting its potential utility in engineering virus resistance.

The Y-1 gene is unique in its action as it induces cell death without preventing the systemic spread of PVY, thus hinting at its possible use in potato breeding. The G-Ry gene, a Y-1 homolog, has been detected to enhance resistance to PVY. Meanwhile, Ny genes, such as Ny-1 and Ny-2, have demonstrated HR against PVY in many potato cultivars. The Nytbr gene exhibits hypersensitivity to PVY, showing necrosis symptoms upon infection. Interestingly, scientists have identified the HCPro cistron of PVY as influencing necrotic reactions and resistance in plants carrying certain resistance genes.

As for resistance to PVX, it is mediated by the Rx1 gene, which causes a rapid termination of viral replication. A transcription factor that interacts with Rx1 mediates antiviral immunity, thereby enabling the Rx1 gene to confer ER to PVX.

One major and two minor quantitative trait loci (QTL) for resistance to potato leaf roll virus (PLRV), a potato disease, have been identified. The major QTL has mapped to potato chromosome XI. These identified genes associated with potato virus resistance can be used for antiviral breeding and for the development of potato varieties resistant to a single virus or many viruses. However, further research is needed to use these resistance genes and to discover new ones.

4. RNAi-Mediated Viral Resistance in Potato

RNA silencing, a common gene regulation mechanism in eukaryotes, plays a central role in protecting against viruses. This mechanism involves the interaction of small interfering RNAs (siRNAs), Dicer-like (DCL) endonucleases, and AGO family proteins. Specifically, DCL4 and DCL2 are responsible for generating siRNAs that mount a defense against RNA viruses. Further amplifying this system, RNA-dependent RNA polymerases (RDRs) convert aberrant single-stranded RNA into double-stranded RNA precursors of secondary siRNAs. This strategy is particularly promising for the development of virus-resistant transgenic plants.

In the specific context of viroid infection in plants, RNA silencing plays an important role. For example, replication of potato spindle tuber viroid in tomato plants induces resistance to RNA silencing, suggesting the critical role of secondary structures in resistance to RNAi.

The process of RNAi silencing can be manipulated to change miRNA sequences, creating artificial miRNAs (amiRNAs) that can target specific sequences. This ingenious approach has been used to engineer virus-resistant plants by creating resistant plants by creating amiRNAs that can actively fight viral infections.

In nature, however, viruses often encode silencing suppressors to counteract host RNAi-based defenses. To improve viral resistance, research is focused on enhancing RNAi activity by increasing the efficiency of AGO proteins and modifying siRNAs.

Despite extensive studies on RNA silencing as a strategy in plant antiviral protection, the beneficial effect of RNA silencing in viral infection remains somewhat puzzling. In particular, the mechanism by which some components of RNA silencing systems contribute to viral infection is not well understood. A deeper understanding of this could open up new opportunities for engineering viral resistance in various crops, such as potato.

5. CRISPR/Cas9-Mediated Viral Resistance in Potato

CRISPR/Cas, a system created to provide immune protection against invading nucleic acids in bacteria, has been repurposed for efficient genome engineering and the development of antiviral immunity in plants. This was amply demonstrated by the ability of CRISPR/Cas systems to effectively control Beet Severe Curly Top Virus (BSCTV) in N. benthamiana and A. thaliana. In addition, the CRISPR/Cas9 system has been ingeniously used to mutate susceptibility genes in rice and tobacco to confer resistance to Rice Tungro Spherical Virus (RTSV) and Potato Virus Y (PVY), respectively.

Besides these applications, the CRISPR/LshCas13a system was used in potato crops to generate resistance to Potato Virus Y, further demonstrating the potential of CRISPR technology in crop protection. Taken together, these studies underscore the significant capacity of CRISPR/Cas9 to control plant RNA viruses in major crops such as potato.

6. Future Prospects and Conclusions

As the battle against genetically complex virus strains in potato varieties escalates, researchers are moving to strengthen virus resistance. They are gearing up for a multi-pronged strategy.

First and foremost, they aim to disrupt the virus-host interaction by editing the potato genome. Using the available potato genome sequences, their goal is to construct an effective shield to protect potato plants from viral invasion. In this regard, they’ve identified CRISPR editing technology as a possible powerhouse in the fight against plant virus infections, a tool that could outperform RNAi.

Second, they are embarking on a mission to discover resistance genes that are key to antiviral response. This discovery could provide a significant boost to potato breeding efforts. Once identified, these genes will be introduced into potato plants through genetic transformation.

Third, they are formulating plans to harness the power of inducible responses in naturally virus-resistant plants. Because these plant defenses have broad-spectrum capabilities, their goal is to identify viral components that activate plant immune mechanisms. This promising area of study could reveal resistance genes that control these protective mechanisms. This, in turn, would pave the way for the development of strategies to engineer the broad-spectrum components of natural defenses.

Fourth, armed with an increasing understanding of the molecular functions of viral proteins, they plan to manipulate these proteins to create cross-protection against further viral infection in potato plants.

Finally, they see the transgenic expression of antiviral proteins of non-plant origin, including antibodies, as a promising frontier in the search for increased resistance to specific potato viruses. This approach underscores the relentless pursuit of new strategies to strengthen potatoes against viral threats.

Source: Liu, J., Yue, J., Wang, H., Xie, L., Zhao, Y., Zhao, M., & Zhou, H. (2023). Strategies for Engineering Virus Resistance in Potato. Plants, 12(9), 1736. https://doi.org/10.3390/plants12091736
Photo: Potato leafroll virus causes stunted plants. Credit Government of Western Australia

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Bioluminescence May Shine Light on Parasitic Nematode Secrets

Posted in Nematodes, RNA on February 25, 2023| Leave a Comment »

 Grahame Jackson

 Sydney NSW, Australia

 For your information

 2 days ago

 0

Bioluminescence May Shine Light on Roundworm Secrets

USDA

For media inquiries contact: Jan Suszkiw
Even though roundworms are nearly too small to be seen, they can pose major problems in corn, soybean, peanut and other crops. Collectively, these roundworms are known as plant-parasitic nematodes, and they cause $173 billion in crop losses worldwide each year.

These losses to crop yield and quality can occur even though chemical controls, resistant cultivars and other methods are available to farmers. So, a team of Agricultural Research Service (ARS) and university scientists decided to take a deeper dive into the basic biology of these nematodes and, more specifically, their genes for reproducing.

But the furtive nature of these millimeter-long pests and peculiarities of their lifecycle evaded the latest high-tech tools that the scientists had hoped to study them with.

Fortunately, they found a “work-around” in the form of electroporation. In short, the technique involves immersing nematodes in a plexiglass chamber with a buffer solution and pulsing it with small jolts of electricity. This stuns the creatures and temporarily opens pores in their bodies through which the solution’s chief “active ingredient” can enter—namely, bits of genetic material called NanoLuc luciferase mRNA.

Luciferase is an enzyme that oxidizes a compound called luciferin, producing a type of light called bioluminescence, such as that emitted by fireflies. In this instance, scientists “retooled” a luciferase coding sequence taken from a bioluminescent, deep-sea shrimp and electroporated it into the nematodes.

“Nematodes have primitive nervous systems,” explained Leslie Domier, a plant pathologist (retired) with the ARS Soybean/Maize Germplasm, Pathology, and Genetics Research unit in Urbana, Illinois. “When they were electroporated, they were immobilized for up to an hour, but then recovered and behaved normally.” Scientists then harvested the nematodes so that the contents of their cells, including luciferase, could be blended into a mixture called a “homogenate.” Next, they mixed the homogenate with a luciferin-like chemical called furamazine and presto—bioluminescence achieved!

Rather than observe this with the naked eye, the scientists used biochemical assays and sensitive light-detecting equipment to gauge the strength of the homogenate’s bioluminescence and determine how well their experiments had worked. So far, the researchers have successfully electroporated luciferase mRNA into the likes of soybean cyst nematodes (SCN) and root-knot nematodes—both costly crop pests—and Caenorhabditis elegans, a free-living species that doesn’t require a host in which to reproduce. 

According to Glen Hartman, another plant pathologist (ARS retired) on the research team, the approach opens the door to introducing other synthetic mRNAs into nematodes to reveal how they change and where, as well as when the nematode’s own genes are activated in cells.

There may be pest-control applications, as well. For example, electroporation could offer a way to rear laboratory colonies of soybean cyst nematodes that carry pieces of genetic code whose sole purpose is to skew the ratio of male- to-female offspring. In theory, releasing these lab-reared nematodes to mate with those in the wild would eventually cause a generational population crash.

“We hypothesized that if we could interfere with the sex determination in nematodes, we could reduce nematode populations below crop-damaging thresholds,” said Domier. That, in turn, could diminish the need for chemical controls or help prolong the effectiveness of elite, resistant cultivars favored by growers, among other potential benefits.

More details about the technique and its implications for nematode control were reported in the journal Molecular & Biochemical Parasitology by Domier, Hartman and co-authors Thanuja Thekke-Veetil and Kris Lambert—both with the University of Illinois—Nancy McCoppin (ARS), Reza Hajimorad (University of Tennessee) and Hyoun-Sub Lim (Chungnam National University).

The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.

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Iron treatment boosts rice immunity to blast

Posted in Fungi, Host plant resistance, RNA on February 25, 2023| Leave a Comment »

FEBRUARY 22, 2023

Iron treatment boosts rice immune system, shows study

by Center for Research in Agricultural Genomics (CRAG)

Iron boosts rice immune system
Rice plant leaves which have been treated or not with iron (5 days) and infected with the fungus M. oryzae. Credit: CRAG

Rice (Oryza sativa L) is the world’s most widely used cereal for human consumption and the second most produced in the world after maize. However, rice production is seriously threatened by rice blast, a fungal disease that has been reported in more than 80 countries on all continents, including the growing areas of almost all rice-producing regions in Spain (Andalusia, Extremadura, Catalonia, Valencia, etc.).

A study recently published in the journal Rice and led by Blanca San Segundo, CSIC researcher at CRAG, has revealed that exposing rice plants to moderately high levels of iron increases resistance to infection by the pathogenic fungus Magnaporthe oryzae, the agent causing rice blast, the most common disease in this crop and responsible for large production losses worldwide.

Iron is an essential nutrient for plant growth and development. Although it is an abundant element in most agricultural soils, its availability to crops might be low. Depending on the soil characteristics, iron is found in its insoluble or soluble form, and therefore the plant can absorb it more or less effectively. In addition, both a deficiency and an excess of iron can become toxic to the plant. Thus, the precise control of the amount of iron as well as its bioavailability turn out to be crucial for the correct growth and productivity of the crops.

Using RNA sequencing methods, which enables the analysis of expression levels of different genes, the research team has detected the activation of several genes related to plant defenses when rice has been treated with iron for a short period of time. In addition, the presence of iron increases the expression of genes related to the generation of phytoalexins, molecules with antifungal activity which are able to inhibit the growth of Magnaporthe oryzae. Thus, it has been possible to demonstrate that a moderate treatment with iron activates the innate immune system of rice.

This work reveals that, under infection conditions, in the leaves of plants treated with iron, an accumulation of both reactive oxygen species (ROS) and iron is observed in specific and very localized regions of the infected leaf, which correspond to the pathogen entry points. This triggers a process of programmed cell death in the plant cells, known as ferroptosis, which limits the progression of the fungus in the infected tissue and therefore the infection is controlled by the plant itself.

“The cell suicide response or ferroptosis has been described in rice varieties resistant to infection by M. oryzae (incompatible interactions). However, it is the first time that this response has been observed in rice plants that are susceptible to infection by this fungus as a result of iron treatment. Iron has a function that enhances the immune response in the rice plant,” says Blanca San Segundo, the leading researcher of the study.

Previous studies by the same group already pointed out that nutrients could play a key role in the resistance or susceptibility to infection by this fungus. The same research team published in 2020 that excess of phosphate, as a consequence of the excessive use of phosphate fertilizers, has the opposite effect since it makes rice more susceptible to infection by the same fungus.

Understanding the relationship between the supply of nutrients (macronutrients and micronutrients) and the defense response of the plant against pathogens can be very useful when designing new protection strategies against blast disease and hence minimize the associated economic losses. In addition, this knowledge will contribute to establish more sustainable practices for growing rice by reducing the use of agrochemicals (fertilizers and pesticides).

More information: Ferran Sánchez-Sanuy et al, Iron Induces Resistance Against the Rice Blast Fungus Magnaporthe oryzae Through Potentiation of Immune Responses, Rice (2022). DOI: 10.1186/s12284-022-00609-w

Provided by Center for Research in Agricultural Genomics (CRAG)

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Australia: Whitefly farming pest in the crosshairs of the same RNA solution behind advanced COVID-19 vaccines

Posted in Control tactics, Insects, RNA on June 24, 2022| Leave a Comment »

ABC RURAL

Whitefly farming pest in the crosshairs of the same RNA solution behind advanced COVID-19 vaccines

ABC Rural

 / By Jodie Gunders

Posted Tue 17 May 2022 at 9:15pmTuesday 17 May 2022 at 9:15pm

Ritesh Jain and Professor Neena Mitter test their new bio clay spray on a plant trial at the University of Queensland. 
Ritesh Jain (left) and Professor Neena Mitter with their non-toxic bio-clay technology.(Supplied: QAAFI)

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The breakthrough RNA technology behind the Pfizer and Moderna COVID-19 vaccines could be set to revolutionise pest control in agriculture, according to new Australian research published in the peer-reviewed Nature Plants journal.

Key points:

  • New technology developed by UQ could provide a solution to hamper the global agricultural pest whitefly
  • A bio-clay spray uses the breakthrough technology behind the Pfizer and Moderna COVID vaccines
  • The RNA technology would allow farmers to target whitefly without the toxicity and residue found in conventional chemical pesticides

The University of Queensland’s Alliance for Agriculture and Food Innovation (QAAFI) said its new bio-clay technology uses double-stranded RNA to protect plants from whitefly, one of global agriculture’s worst pests.

“What we are doing is targeting the essential genes of the whitefly by using their own RNA,” said research team leader Professor Neena Mitter.

“We use clear particles as carriers, so it’s almost like nature versus nature, using the RNA from the whitefly to kill the whitefly itself and using degradable clay particles as the delivery vehicle.”

Professor Mitter said the five-year research project aimed to target a significant pest in a way that was environmentally friendly and free of the toxicity and residue found in conventional pesticides.

Getting to the root of worldwide pest

Close-up of a whitefly.
The whitefly is destroying half of East Africa’s main food source, and yet it’s no bigger than the head of a pin.(Supplied: Laura Boykin)

Whitefly is a sap-sucking pest affecting multiple crops including cotton, pulses and vegetables.

Professor Mitter said it was responsible for both crop damage and the transmission of more than 200 viruses.

“Not only can the adult whitefly pick up the RNA, but this technology can target multiple life stages so the eggs won’t hatch, the nymphs won’t develop properly,” she said.

“This is the first time we’ve been able to target multiple life stages through RNA.”

Professor Mitter said the cost of producing RNA had decreased significantly over the past five years thanks to an increase in the number of companies working with the technology.

“When I started working with RNA my worry was that we would not be able to make it in a cost-effective manner,” she said.

“The price we are getting now may be $2 to $5 per gram, as opposed to nearly $2,000 per gram when we first started this work.”

a man spraying a plant with a small spray bottle.
PhD candidate Ritesh Jain using the environmentally friendly spray.(Supplied: QAAFI)

But the growth of RNA technology did not begin with the development of human vaccines, Professor Mitter said.

“This work on RNA production for agriculture, or double stranded RNA, started way earlier than the COVID vaccine [and] mRNA technologies.

“Those companies were actually working on producing RNA for agriculture and then shifted,” she said.

Testing comes next

The bio-clay technology must still pass research and development hurdles before it can be adopted by industry, with trials set to begin under greenhouse conditions.

“It does open us a window now to test it in protected cropping or controlled environment agriculture,” Professor Mitter said.

“We know that a large number of crops like tomatoes, cucumbers, and others are being grown in greenhouse conditions and this technology should work very well.”

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Senior research and development manager at the Cotton Research and Development Corporation, Susan Maas, said whitefly was also a major pest for the cotton industry due to its ability to contaminate and downgrade lint quality.

But she said QAAFI’s solution would not be commercially viable for some years and price would be a factor.

“It’s too early to say, but any product will need to be competitive[ly priced] for farmers,” she said.

“We anticipate that bio-clay will add to the options farmers have for pest and disease control, expanding the tools they have available.”

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Australia: Enviro-friendly spray targets crop killer

Posted in Insects, RNA on May 18, 2022| Leave a Comment »

Enviro-friendly spray targets crop killer

Canberra Times

By Liv Casben

Updated May 16 2022 – 11:06pm, first published 11:02pm

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Ritesh Jain (left) and Neena Mitter say the chemical-free spray only targets silverleaf whitefly.

An environmentally friendly spray targeting one of the world’s most damaging agricultural pests has been created by Australian scientists.

Heralded as a crop production game-changer, the technology is chemical free and has been developed by University of Queensland researchers over the past decade.

Research team leader Neena Mitter said it was a breakthrough for crop protection because it was effective against silverleaf whitefly, a small insect responsible for the loss of billions of dollars in crops around the world.

The whitefly attacks more than 500 plant species including cotton, pulses, chilli, capsicum, and many other vegetable crops.

“We silence the genes of whitefly using their own RNA,” Professor Mitter told AAP.

RNA is a molecule present in all living cells that has structural similarities to DNA.

The scientists sprayed the RNA on the plant so when the insect feeds it kills them. The RNA is specific to the targeted species.

Prof Mitter said the research, published in the scientific journal Nature Plants on Tuesday, had worked out how to silence genes in the pest and is carried in an environmentally friendly clay called BioClay.

“If we want to kill whiteflies we make the RNA specific to whitefly, if we want to kill another insect we make the RNA specific to that,” she said.

“The insect lays eggs on the underside of the leaves and the nymphs and adults suck the sap from the plant resulting in reduced yields.

“The uniqueness of our technology is partnering the RNA with clay particles … which makes it possible for the RNA to last longer on the plants so it does not get washed off by rain, it sticks to the leaves and slowly releases the RNA.

“The world wants to move away from chemical pesticides and this is one of the tools.”

To identify suitable gene targets, PhD candidate Ritesh Jain went through the global database of genome sequences.

“Initially, we had to screen hundreds of genes specific to SLW (silverleaf whitefly) to see which ones would affect their growth,” Mr Jain said.

“Importantly, the RNA proved harmless when fed to other insects, such as stingless bees and aphids.”

Susan Maas from the Cotton Research and Development Corporation said silverleaf whitefly was a major pest for cotton across the globe due to its ability to contaminate and downgrade lint quality.

She said the technology was a game-changer for the cotton industry.

“It is highly specific to the target pest, in this case it is whitefly, so that any impact on beneficial crop insects is negligible,” Ms Maas said.

“It also has a very low impact on the environment with no residues remaining after application.

“BioClay sets up a framework for the potential development of other targeted pest specific products in the future, tackling different pest control challenges in a highly focused, environmentally safe way.”

Cotton Australia Chief Executive Adam Kay said growers were also involved in the project and shared their on farm experience.

“This development is an exciting breakthrough for cotton farmers and all farmers impacted by whitefly.”

Australian Associated Press

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Fighting Plant Pathogens with RNA

Posted in Biotechnology, Fungi, RNA on September 22, 2016| Leave a Comment »

ucr-today

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

By on September 20, 2016

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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How the Rice Brown Planthopper Switches from Sluggish Super Breeder to Flying Invader

Posted in Biotechnology, Insects, Research, RNA, tagged , on March 24, 2015| Leave a Comment »

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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New Insecticidal Strategy Kills Crop Pests With RNA Interference

Posted in Research, RNA, tagged , , on March 4, 2015| Leave a Comment »

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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KSU research: Helping Wheat Defend Itself Against Damaging Viruses

Posted in Biotechnology, Research, RNA, Viruses, tagged , , , on November 19, 2014| Leave a Comment »

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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Plants can ‘switch off’ virus DNA

Posted in Crop protection, Research, RNA, tomato yellow leaf curl virus, TYLCV, Uncategorized, Viruses, Weeds, tagged , , , , on August 26, 2014| Leave a Comment »

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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