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Archive for the ‘Insect-plant interaction’ Category

Wednesday, 12 January 2022 14:02:00

From PestNet

Grahame Jackson posted a new submission ‘Device Sniffs Out the “Smell-fingerprints” of Pestered Plants’

Submission

Device Sniffs Out the “Smell-fingerprints” of Pestered Plants

USDA ARS

For media inquiries contact: Jan Suszkiw, (202) 734-1176
January 11, 2022

A team of Agricultural Research Service (ARS) and university scientists has developed an electronic nose to sniff out whitefly infestations of tomato plants.

The “E-Nose” works by detecting a specific cocktail of chemicals, called volatile organic compounds (VOCs), that tomato plants release into the air when attacked by whiteflies.  In nature, these chemicals put other plants on high alert. Scientists are hoping the E-nose will also warn growers so they can fine-tune their use of whitefly-killing insecticides, biocontrol agents like parasitic wasps or other measures.  

According to Heping Zhu, an agricultural engineer with the ARS Application Technology Research Unit in Wooster, Ohio, who co-developed the E-nose with collaborators at The Ohio State and University of Tennessee-Knoxville, whiteflies are top insect pests of U.S. fresh-market tomatoes, which were valued at $721 million in 2020.

Left unchecked, adult whiteflies and their immature nymphs probe the undersides of tomato plant leaves for sap, causing them to turn yellow, curl or drop off. Whitefly feeding can also cause uneven ripening of fruit and transmit viral diseases that weaken the plants further. 

Whitefly monitoring typically involves checking for a threshold number of the pests per leaf on a sampling of plants or captured in sticky traps—both a time-consuming process. 

Towards that end, the researchers designed a prototype E-nose device about the size of a shoebox that can operate in the greenhouse. According to Zhu, the device mimics the mammalian sense of smell and brain’s ability to recognize certain odors. But instead of a nasal passage, receptor cells and an olfactory bulb, the E-nose uses gas sensors, data acquisition modules and other components.

A key feature of the E-nose is a nerve-like circuitry board that helps convert VOC samples from the air into digital signals. These signals in turn are transmitted to the system’s “brain,” namely, a mathematical algorithm programmed to recognize specific types and concentrations—or “smell-fingerprints”—of VOCs that tomato plants give off when attacked. 

In greenhouse tests, the E-nose displayed the VOC fingerprints of such plants as different lines with different colors that rose sharply and steadily to the right of an LED screen. Moreover, the system distinguished the smell-fingerprints of whitefly-infested tomato plants from un-infested ones, as well as plants whose leaves were punctured with pins for comparison. 

With additional testing and development, the E-nose could give greenhouse growers another monitoring tool to use in deciding where, when, and how best to tamp down whitefly infestations before they reach economically damaging levels. Besides whiteflies, the E-nose also successfully sniffed out tomato-infesting aphids and insect pests of other greenhouse crops.

“The future E-nose system can be designed as a hand-held device for growers to take samples from individual plants,” Zhu said. “It can also be designed as a computer-controlled cloud networking system which consists of multiple smart sensors placed at different locations in the greenhouse, so the computer can automatically collect samples and monitor infestations 24 hours a day.”

Details of the team’s findings were published in the October 2021 issue of Chemosensors and in the August 2019 issue of Sensors.

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 agricultural research results in $17 of economic impact.


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Monarchs evolved mutations to withstand milkweed toxins; so did their predators

by University of California – Berkeley

What it takes to eat a poisonous butterfly
A cluster of monarch butterflies overwintering in California. Credit: Mark Chappell, UC Riverside

Monarch butterflies and their close relatives thrive on poisonous milkweed, thanks to genetic mutations that block the effects of the plant’s toxins while allowing the poisons to accumulate in the caterpillar or adult insects as deterrents to hungry predators.

Turns out some of those insect-eating predators evolved similar mutations in order to feast on monarchs.

In a study appearing this week in the journal Current Biology, researchers at the University of California, Berkeley, and UC Riverside report monarch-like genetic mutations in the genomes of four organisms that are known to eat monarchs: the black-headed grosbeak, a migratory bird that snacks on the butterflies at their overwintering home in Mexico; the eastern deer mouse, a close relative of the Mexican black-eared deer mouse that feeds on butterflies that fall to the ground; a tiny wasp that parasitizes monarch eggs; and a nematode that parasitizes insect larvae that feed on milkweed.

All four organisms have evolved mutations in one or more copies of a gene for the sodium-potassium pump—the same mutations, in fact, as milkweed butterflies, and ones that the researchers and their collaborators showed two years ago were critical to the monarch’s ability to eat milkweed without succumbing to its toxins.

The toxins are cardiac glycosides that interfere with this pump, which helps enable heartbeats and nerve firing. It’s so important in humans that we use a third of all the energy we generate from food to power the pump. It’s not surprising, then, that when the toxins throw a wrench in the pump, the heart and other organs stop, too. Even horses and humans can die of cardiac arrest if they consume enough of the milkweed toxins, which are still used as an arrow poison by hunter-gatherer groups in Africa. Until recently, small amounts of related chemicals from foxglove were widely used to treat congestive heart failure.

“The toxins move up the food chain from plants—what biologists call the first trophic level—to insect herbivores, the second, and then to predators and parasitoids—a third trophic level,” said evolutionary biologist Noah Whiteman, UC Berkeley professor of integrative biology and of molecular and cell biology. “In response, the predators and parasitoids have evolved resistance to the toxins at the same sites that we discovered were changing in the monarch, and sometimes to the same amino acids. This might be the first time that the same resistance mutations have been found in the third and second trophic levels that evolved in response to the latter feeding on toxic plants. “

“It’s remarkable that convergent evolution occurred at the molecular level in all these animals,” said co-author Simon “Niels” Groen, assistant professor of evolutionary systems biology in UC Riverside’s nematology department and a former UC Berkeley postdoctoral fellow. “Plant toxins caused evolutionary changes across at least three levels of the food chain.”

What it takes to eat a poisonous butterfly
In places like Mexico where monarch butterflies overwinter by the thousands to millions, the black-headed grosbeak is one of few birds that can eat them without vomiting. Researchers discovered that the bird has evolved similar genetic mutations as those found in the monarch that allow both to handle milkweed toxins, which accumulate in the butterfly and are deterrents to most predators. Credit: Mark Chappell, UC Riverside

Birds do it, wasps do it. Even nematodes do it.

Since the 1980s, biologists have known that monarchs and a few other butterflies, and even some beetles, aphids and other insects, have adapted to feeding on milkweed plants and storing the toxins in their bodies—even through metamorphosis—to deter predators. In the last decade, geneticists tracked down the actual genetic mutations that allowed this, all of which were in the sodium pump and allowed the pump to work, despite the toxins. Whiteman speculated that those animals that eat the butterflies must have evolved resistance mutations as well. But were they the same?

When the genome of the black-headed grosbeak was published last year, Whiteman and Groen immediately looked for and found sodium pump mutations nearly identical to those that evolved in the monarch. The researchers subsequently expanded the study, scanning previously sequenced genomes from other monarch-eating animals, and found similar mutations.

The black-headed grosbeak (Pheucticus melanocephalus), a summer resident of California, migrates to Mexico and is known for gobbling up monarchs at the places where they overwinter in the mountains of Michoacán state. One study found that the black-headed grosbeak and another bird, the black-backed oriole (Icterus abeillei), consumed hundreds of thousands to 1 million monarchs over a single winter.

It was evident from their behavior, however, that the two birds were not equally resistant to the milkweed toxins stored in the butterfly’s body. While the grosbeak would tear off the wings and consume the abdomen whole, the oriole would gut the abdomen after de-winging the butterfly and eat only the insides. The outside, or cuticle, has a higher concentration of cardiac glycoside toxins, as do the wings. Orioles also discarded monarchs with higher levels of cardiac glycosides.

The new study reveals how the grosbeak can tolerate the toxins in the monarch: It has evolved single-nucleotide mutations in its sodium pump genes in two of the same three locations where monarchs evolved mutations that help make them the most resistant organism to the milkweed’s cardiac glycosides. None of the other 150 or so sparrow-related “passerine” birds whose genomes are known has these mutations in both of the most widely expressed copies of the sodium pump gene. The oriole’s genome has yet to be sequenced.

What it takes to eat a poisonous butterfly
This graphic shows how milkweed toxins move from the plant through monarch caterpillars and butterflies into the black-headed grosbeak that feasts on them. To become resistant to the toxins, the grosbeak evolved mutations in its sodium pump (lower left) that are identical to two of the three mutations the monarch itself developed to make it resistant. Credit: UC Berkeley image by Julie Johnson

“It solves this mystery from 40 years ago where the biology was pretty well worked out, but we just couldn’t go down to the lowest level of organization possible, the genome, to see how grosbeaks are doing this,” Whiteman said. “It looks like, amazingly, they are evolving resistance using the same kind of machinery in the same places in the genetic code as the monarch and the aphids, the bugs and the beetles, that feed on milkweeds, as well.”

The biologists found that the wasp (Trichogramma pretiosum) also has two mutations in the same place as the monarch in the sodium pump gene. The nematode (Steinernema carpocapsae) has changes at all three locations in the sodium pump gene that also evolved in the monarch butterfly, including the one location that confers the most resistance. These nematodes have been found in the soil around milkweed plants in New York and may parasitize the grubs of beetles that feed on milkweed roots and presumably the larvae of other insects, including butterflies.

The fact that the eastern deer mouse (Peromyscus maniculatus)—a close relative of the black-eared deer mouse (P. melanotis), a monarch-feeding specialist—has all three mutations in its most widely expressed copies of the sodium pump gene was already known and not surprising, Whiteman said. The rat and other rodents have mutations in their sodium pump genes that allow them to resist cardiac glycosides and other substances that would be toxic to other mammals.

It’s unclear whether there are additional adaptations that help the black-headed grosbeak and other monarch predators like the black-eared deer mouse deal with the toxins, Groen said. He is planning to explore this question in future studies. Whiteman suspects that other organisms in the food chain that starts with milkweed will be found to have mutations similar to those found in the monarch.

“My guess is, there are other parasitoids out there, and predators that have also evolved resistance mutations that are interacting with monarchs, and it’s just a matter of time before they’re discovered,” he said. “We know that this isn’t the only way to evolve resistance to cardiac glycosides, but it seems to be the predominant way—targeting this particular pump.”


Explore furtherScientists recreate in flies the mutations that let monarch butterfly eat toxic milkweed with impunity


More information: Convergent evolution of cardiacglycoside resistance in predators and parasites of milkweed herbivores, Current Biology (2021). doi.org/10.1016/j.cub.2021.10.025Journal information:Current BiologyProvided by University of California – Berkeley

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Complexity Untangled: For Plant Defenses, Pest Attack Order Matters

ENTOMOLOGY TODAY1 COMMENT

A study on insect pests of pea plants finds that which pest attacks first changes how the plant mounts defenses, how effective those defenses are, and the eventual nutritional quality of the plants. The experiment examined scenarios in which pea plants were first attacked by pea aphid (Acrythosiphon pisum, left) and pea leaf weevil (Sitona lineatus, right). Pea aphid also affects plants by transmitting pea enation mosaic virus. (Aphid photo by Joseph Berger, Bugwood.org; weevil photo by Pest and Diseases Image Library , Bugwood.org)

By Saumik Basu, Ph.D.

The order of arrival and feeding of different insect pests impact a plant’s ability to fight back by altering its defense response and nutritional quality. My colleagues and I have unfolded the complexity of these interactions in our research to understand potential implications in pest control strategies.

The Palouse region of eastern Washington and northern Idaho is home for cultivation of cool-season legumes such as peas, lentils, chickpeas, and fava beans. A piercing-sucking vector herbivore, pea aphid (Acyrthosiphon pisum) and an aphid-borne pathogen, pea enation mosaic virus (PEMV), have long worried farmers in the Palouse with crop yield loss ranging from 30–40 percent and major outbreaks of pea aphids reported every 6–9 years. In addition to the pea aphid-PEMV mediated pathosystem, a more innocuous-seeming, chewing, non-vector herbivore, the pea leaf weevil (Sitona lineatus), takes tiny feeding bites from pea leaves and has also been found to significantly affect plant susceptibility. These organisms co-occur in the Palouse region, and interactions between them can affect plant signaling pathways and nutritional status.

Saumik Basu, Ph.D., is a postdoctoral research associate in the Department of Entomology at Washington State University in Pullman, Washington. (Photo courtesy of Saumik Basu, Ph.D.)

Pea leaf weevil adults overwinter outside of pea fields and migrate into fields in the late spring to lay eggs. After hatching of eggs, larvae burrow into the soil to feed and pupate before adults re-emerge in the summer and continue feeding on peas. First-generation pea leaf weevil adults typically attack plants before arrival of pea aphids and PEMV, but second-generation pea leaf weevils typically attack plants after pea aphid and PEMV have arrived. However, the responses of pea plants based on the number of stressors and their order of attack and the underlying molecular mechanisms that mediate these interactions are largely unknown.

Many studies have already investigated the effects of single pest on plants. But managing multiple pests concurrently is highly challenging. Our recent study published in August in Molecular Ecology is among the few published works that investigate complex plant-mediated interactions of multiple biotic stressors. To better understand plant responses to multiple stressors and to assess how these responses are affected by order of arrival of stressors and food web complexity, we investigated the response of pea plants to various attack sequences from these two pests and PEMV.

In a series of greenhouse experiments performed in collaboration with colleagues at Washington State University and Cornell University, we investigated what happens to pea plants when they face different sequences of pest attacks and virus exposure. We created experiments in which weevils and then pea aphids feasted on pea plants, and we contrasted the results with the reverse attack order. We also included scenarios where some pea plants were infected with PEMV while others remained uninfected. After removing the pests, we let the plants grow, and then we measured the plant’s defense phytohormone levels, expressions of associated defense genes, and nutritional status.

We found that, when pea leaf weevils feast on peas first, it enhances some of the anti-pathogen defense responses of the pea plants, helping them to become more resilient to PEMV infection. But, when the weevilsdine after the aphids, it lowers the anti-pathogen defenses, allowing the virus to spread more easily. In turn, PEMV-infected plants had stronger anti-herbivore defense responses, since they induce production of compounds that interfere with the pest feeding. Further complicating the issue, we also found in this study that, when weevils induced anti-pathogen defense responses, the nutritional quality of pea plants was lowered by decreasing the plant’s available amino acids.

pea aphids
pea aphids

We strongly believe that these complex interactions convey important implications to design sustainable pest- and pathogen-management strategies. If we know beforehand when these interactions are happening, that information will give farmers a best possible remedy to prevent their fields from these attacks by choosing proper timing, using appropriate pest control agents, and controlling the pests during the most susceptible stage of their life cycles. While using broad spectrum insecticides (e.g., pyrethroids) may enhance pest management efficiency against multiple pests in different attack orders, this approach comes with problems associated with non-target insects. Better understanding of the dynamics of pest-attack orders, however, can allow for more effective use of targeted approaches, such as biological control agents (e.g., lady beetles); pesticides that are less harmful to natural enemies, non-target insects, and pollinators; and biofertilizers (e.g., soil mutualistic rhizobia).

This study is a part of our ongoing series of investigations to assess complex interactions among many organisms that a plant may encounter in a food web ecosystem. Our earlier study published in May in Functional Ecology investigated the antagonistic relationship between PEMV and a root-colonizing and nitrogen-fixing bacteria called rhizobia. Our next study in this series looks at the interactions between the pea leaf weevil and soil rhizobia.

These complex relationships of multiple biotic stressors are crucial to understanding how plants respond to these attackers and are critical for developing sustainable management strategies against devastating pests and pathogens to boost crop yield and agroeconomy.

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Responses of pea plants to multiple antagonists are mediated by order of attack and phytohormone crosstalk

Molecular Ecology

Saumik Basu, Ph.D., is a postdoctoral research associate in the Department of Entomology at Washington State University in

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WUR research finds: Plants can prepare for insect attack sequence

Plants are under attack by a variety of insect species. They have defence mechanisms to deal with this, including chemicals or sturdier leaves. It has now been found that, when wild black mustard plants defend themselves against an initial enemy, they already anticipate the need to later fend off other, different enemies. In fact, they even prepare for the most likely sequence of attackers. This research has now been published in the scientific journal Nature Plants.

The article is based on doctoral research carried out by Daan Mertens and Maite Fernandéz de Bobadilla, working in the team headed by Erik Poelman, associate professor in the Laboratory of Entomology at Wageningen University & Research.

“We’re increasingly moving towards sustainable forms of agriculture and horticulture, which includes drastically reducing the use of pesticides,” says Poelman. “For arable farmers, that means having to deal with a greater variety of insects attacking their crops. Plant breeders used to focus on resistance to the most problematic insects, while broad-spectrum pesticides were used to deal with other herbivores. Now we have to change our approach, and in doing so we can learn from wild plant species and how they deal with a diversity of insects.”



This is a substantial change of direction, explains Mertens. “Previously, there would be a focus on breeding plants that deal with a specific insect problem. Now, plant breeding has to create crops that are flexible in their defences and can deal with all kinds of enemies. It’s about moving toward a systems approach.”

Specific reaction for each enemy
Plants can never be sure if or when they will be subjected to an attack. Most species resolve this uncertainty by only fully investing in defences (such as the production of defensive chemicals) when they are actually being attacked. This means that, when herbivorous insects are absent, the plants can fully invest their resources (products of photosynthesis such as sugars and starch) into their own growth and reproduction.

“Plants have a fairly specific sense of which insects are attacking them,” says Mertens. “They notice insect attack from the way the cells are damaged, the compounds that are then released, and the characteristics of the insects’ saliva. They can interpret those signals to mount a targeted defence.”

However, the defences targeted at one insect species may not be effective against attack by other insect species.

An added complication is that a plant’s specific reaction to aphids, for example, can reduce its resistance to caterpillars, as plants have a variety of mechanisms to develop different kinds of defences. These mechanisms are triggered by plant hormones that may interact when regulating a defence response.

How do plants defend themselves against multiple attacks from herbivores? (WUR)

Risk management
So how can a wild plant, with insects literally swarming around it, still manage to look after itself so well? “They’re prepared for the damaging insects to arrive in a specific sequence,” says Mertens. “Early in the season it might be a particular species of aphid, and later a particular species of caterpillar. They organize their defences and ensure that they can deal with these different insects over time. It seems like a conscious form of risk management, but it has emerged through natural selection. They can handle the most common sequence of events.”

By means of an unusually large experiment, the researchers showed that this is indeed how the plant’s strategy works. They observed the defence mechanism used by black mustard on 90 combinations of insect attacks and linked these results to three years of research into the frequency of the interactions on plants in the wild. Similar tests in the past were limited to perhaps five combinations.

This ambitious approach has resulted in valuable new insights. “We’ve linked our understanding of plant physiology to ecology,” explains Poelman. “The old idea that insects feeding on plant sap trigger a reaction which then diminishes a plant’s potential defence against caterpillars has turned out to be too simple. Our work confirms research on the physiological reactions of the plant against aphids and caterpillars, but also reveals that in many instances the plant does not become more susceptible to insects with a different feeding pattern. The presence of a particular combination or sequence of insects in the wild appears to be a better predictor of resistance than the characteristics of the individual insect species.”

For more information:
Wageningen University & Research
www.wur.nl 

Publication date: Tue 19 Oct 2021

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New species has longest tongue of any insect

Malagasy moth uses its giant proboscis to get into orchids

A long proboscis of a Wallace Sphinx moth compared to a Morgan’s Sphinx moth
© PATRICK BASQUIN/ALEXANOR

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On the island of Madagascar there lives a large moth with a tongue long enough to make Gene Simmons green with envy. Its name? Xanthopan praedicta. Its business? Sucking the pollen out of a very long and skinny orchid.

This moth’s whole history is absurd. Charles Darwin predicted its existence when he first saw the shape of the Angraecum sesquipedale orchid (which apparently prompted him to exclaim, “Good heavens, what insect can suck it?”). About 2 decades later, in 1903, the moth was actually discovered, and ever since, the Malagasy variant has been considered a subspecies of its mainland counterpart, X. morganii. But no longer.

Using a slew of morphological and genetic tests, scientists argue the island moth is substantially different enough from its mainland counterpart to merit its elevation to the species level, the Natural History Museum announced yesterday.

Working with a combination of wild moths and museum specimens, the team reports that DNA barcoding, a technique that can be used to identify organisms by looking at DNA sequence differences in the same gene or genes, shows the moth’s genetics differ by as much as 7.8% in key gene sequences, which actually makes the morganii moths more closely related to a few other mainland subspecies than praedicta.

But what about the tongues? The Malagasy moths take the prize here, with proboscises that measure 6.6 centimeters longer on average, as seen in the picture above. Adding to their legend, the team also reported finding one individual praedicta specimen with a proboscis that measured a whopping 28.5 centimeters when fully stretched, which would constitute “an absolute record” for any moth tongue ever measured. Congratulations!


doi: 10.1126/science.acx9280

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David Shultz

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How Insect Saliva is Helping Crops Protect Against Pest Damage

Cowpea is one of Africa’s most important cash crop, and has been found to detect larvae and reduce feeding damage (Image by Toby Hudson)

A new study has unlocked the hidden ways in which important cash crops such as cowpea (Vigna unguiculata) tackle localised pest invasion and damage using natural defence mechanisms. Insights such as these are key for the future protection of our global agricultural production in the light of increasing pest outbreaks and crop damage.

Scientists have published research in which they have found an immune receptor in cowpea cells that can detect the saliva of caterpillars feeding on their leaves, causing a series of natural defence responses such as the release of chemicals that limit the rapid growth capabilities of the larvae. An example of such a defence mechanism is found when the bean pod borer (Maruca vitrata) larvae feed on cowpea, causing the release of a pheromone which attracts parasites to then feed on the larvae.

“Despite chemical controls, crop yield losses to pests and diseases generally range from 20 to 30 percent worldwide. Yet many varieties are naturally resistant or immune to specific pests,” explains biologist Adam Steinbrenner from the University of Washington. “Our findings are the first to identify an immune recognition mechanism that sounds the alarm against chewing insects.”

As of yet, very little is known about how plants are able to identify and combat pest threats, however this new study which is built on previous research by the same team has found that certain peptides known as inceptins are found in the saliva of the larval pests such as the beet armyworm (Spodoptera exigua) larvae – which is one of greatest threats to cowpea crops across Asia and North America. The beet armyworm is native to Southeast Asia and has colonised parts of America since the late 1800s. This pest is extremely damaging to crop foliage, with larvae being found to consume more than other major crop pests such as the diamondback moth (Plutella xylostella).  

Beet armyworm larvae (Image by Russ Ottens, University of Georgia)

The inceptins are the spark that causes the cowpea defence mechanisms against feeding pests, ultimately resulting in larval damage or death. The research found inceptin receptors (INRs) on cowpea plant calls specifically. Unfortunately, there are limited ways to study cowpea crops, resulting in the team having to use tobacco plants to test how the INRs work in practice.

By inserting the gene for INR production into tobacco crops, the team were able to test what would happen in the presence of armyworm larvae. It was found that the INRs were triggered in response to the presence of certain protein fragments in the saliva of feeding caterpillars, as well as in response to direct feeding damage on leaves. The fragments of saliva protein that caused the defence response was found to be pieces of cowpea proteins that were broken down by the caterpillar during feeding. In the tobacco test crops, the presence of these proteins triggered the release of a plant hormone that is known to occur when under threat, resulting in the suppression of insect growth.

“Like many plant immune receptors, this receptor is encoded only by certain plant species but can be transferred across families to confer new signalling and defence functions,” the author wrote.

With the genomic techniques used in this study, the team were able to discover hidden information about plants natural defence mechanisms against pest damage. With the increasing global demand for food as well as more prevalent agricultural pest outbreaks, such studies must be conducted on numerous important food crops and a variety of environmental climates so we can better prepare for and mitigate future threats.

If you would like to read more on this subject, please see the links below:

armywormbeet armywormcowpeaAgriculture and International DevelopmentCrop healthFood and nutrition securityPlant Sciences

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Tomato fruits send electrical warnings to the rest of the plant when attacked

A recent study in Frontiers in Sustainable Food Systems shows that the fruits of a type of tomato plant send electrical signals to the rest of the plant when they are infested by caterpillars. Plants have a multitude of chemical and hormonal signaling pathways, which are generally transmitted through the sap (the nutrient-rich water that moves through the plant). In the case of fruits, nutrients flow exclusively to the fruit and there has been little research into whether there is any communication in the opposite direction–i.e. from fruit to plant.

“We usually forget that a plant’s fruits are living and semiautonomous parts of their mother plants, far more complex than we currently think. Since fruits are part of the plant, made of the same tissues of the leaves and stems, why couldn’t they communicate with the plant, informing it about what they are experiencing, just like regular leaves do?” says first author Dr. Gabriela Niemeyer Reissig, of the Federal University of Pelotas, Brazil. “What we found is that fruits can share important information such as caterpillar attacks–which is a serious issue for a plant–with the rest of the plant, and that can probably prepare other parts of the plant for the same attack.”

To test the hypothesis that fruits communicate by electrical signals, Niemeyer Reissig and her collaborators placed tomato plants in a Faraday cage with electrodes at the ends of the branches connecting the fruits to the plant. They then measured the electrical responses before, during and after the fruits had been attacked by Helicoverpa armigera caterpillars for 24 hours. The team also used machine learning to identify patterns in the signals.

The results showed a clear difference between the signals before and after attack. In addition, the authors measured the biochemical responses, such as defensive chemicals like hydrogen peroxide, across other parts of the plant. This showed that these defenses were triggered even in parts of the plant that were far away from the damage caused by the caterpillars.

Read the complete article at www.eurekalert.org.

Reissig Gabriela Niemeyer, Oliveira Thiago Francisco de Carvalho, Oliveira Ricardo Padilha de, Posso Douglas Antônio, Parise André Geremia, Nava Dori Edson, Souza Gustavo Maia, “Fruit Herbivory Alters Plant Electrome: Evidence for Fruit-Shoot Long-Distance Electrical Signaling in Tomato Plants” Frontiers in Sustainable Food Systems 5 (2001) DOI=10.3389/fsufs.2021.657401 https://www.frontiersin.org/article/10.3389/fsufs.2021.657401

Publication date: Mon 9 Aug 2021

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Science Newsfrom research organizations


Fruit fly offers lessons in good taste

Study shows food choice decisions require taste input

Date:July 27, 2021Source:University of California – RiversideSummary:The fruit fly has multiple taste organs throughout its body to detect chemicals, called tastants, that signal whether a food is palatable or harmful. It is still unclear, however, how individual neurons in each taste organ act to control feeding. To explore this question, a team used the fly pharynx as a model to study whether taste information regulates sugar and amino acid consumption at the cellular level.Share:FULL STORY


What can the fruit fly teach us about taste and how chemicals cause our taste buds to recognize sweet, sour, bitter, umami, and salty tastes? Quite a lot, according to University of California, Riverside, researchers who have published a study exploring the insect’s sense of taste.

“Insect feeding behavior directly impacts humans in many ways, from disease-carrying mosquitos that seek human blood to pests whose appetite can wreak havoc on the agricultural sector,” said Anupama Dahanukar, an associate professor of molecular, cell and systems biology, who led the study appearing in the Journal of Neuroscience. “How insect taste neurons are organized and how they function is critical for a deeper understanding of their feeding behavior.”

The fruit fly has multiple taste organs throughout its body to detect chemicals, called tastants, that signal whether a food is palatable or harmful. It is still unclear, however, how individual neurons in each taste organ act to control feeding. To explore this question, Dahanukar’s team used the fly pharynx as a model to study whether taste information regulates sugar and amino acid consumption at the cellular level.

Dahanukar explained animals rely heavily on the sense of taste to make feeding decisions, such as consuming nutritive foods while avoiding toxic ones.

“In mammals, taste information is encoded by specialized cells present in taste buds of the tongue,” she said. “Taste receptors expressed in these cells can detect different chemicals. Molecular and functional differences in receptors expressed in different cells allow recognition of different tastes, such as salty, sour, sweet, bitter, or umami.”

Several new studies in flies indicate individual taste neurons can detect compounds belonging to more than one taste category, raising some questions about the distinct behavioral roles of individual taste neurons. If many classes of taste neurons are activated by sugar, for example, how does activation of just one class of taste neurons affect behavior?

Dahanukar’s team answered this question by genetically engineering a fly in which only a single defined class of pharyngeal neurons is active. The team then tested this fly in different feeding experiments to understand what the fly can or cannot do compared to animals that have all their taste neurons intact.

“We found single-taste neurons are capable of responding and activating behavioral responses to more than one tastant category — sweet and amino acids in our study,” said Yu-Chieh David Chen, the first author of the research paper. “We also found that a single tastant category — amino acids in our study — can activate multiple classes of taste neurons.”

The team also tested flies that had no functional taste neurons. Such flies were incapable of making any proper feeding decisions, no matter the food choices — whether these were two attractive stimuli, one attractive and one aversive, or one nutritive and the other nonnutritive.

The researchers found food choice decisions cannot be made in the absence of taste input; the latter is critical for ensuring appropriate food choice and feeding behavior. Further, flies that had pharyngeal sweet taste neurons as the only source of taste input were consistently able to select more palatable food.

“Altogether, our results argue for the existence of a combinatorial coding system, wherein multiple neurons coordinate the response to any given tastant,” Dahanukar said.

The study is the first to directly test the impact of loss of all taste neurons on behavioral responses to tastants of different categories. It is also the first to test whether a single class of taste neurons is sufficient for food choice and feeding behavior.

“Along with several other recent studies in the field, our work also invites revisiting some established ideas about how insect taste is organized,” Dahanukar said. “Rather than encoding tastes as in mammals, flies appear to encode some combination of valence — attractive versus aversive — and tastant identity.”

Her team anticipates that knowing how taste neurons work in flies will facilitate insect studies of greater health or agricultural importance.

“We are building tools for asking the same sorts of questions in mosquitoes,” Dahanukar said. “Such studies could offer potential targets for manipulating feeding behaviors of pests or disease vectors in surveillance or control strategies.”

She acknowledged that her lab has only evaluated a single taste neuron within the system it set up, with many more remaining to be studied.

“We are interested in understanding what these neurons sense and how they act, individually and as part of a group, to control parameters that lead to either promotion or cessation of food intake,” said Vaibhav Menon, a graduate student in Dahanukar’s lab and a co-author on the study.

The team plans to apply some of the same strategies to investigate how feeding behavior is controlled in mosquitoes.

The study was supported by the Whitehall Foundation, National Institutes of Health, National Institute of Food and Agriculture of the U.S. Department of Agriculture, and UCR Agricultural Experimental Station. Chen was a Howard Hughes Medical Institute International Student Research Fellow at UCR.


Story Source:

Materials provided by University of California – Riverside. Original written by Iqbal Pittalwala. Note: Content may be edited for style and length.


Journal Reference:

  1. Yu-Chieh David Chen, Vaibhav Menon, Ryan Matthew Joseph, Anupama Arun Dahanukar. Control of Sugar and Amino Acid Feeding via Pharyngeal Taste NeuronsThe Journal of Neuroscience, 2021; 41 (27): 5791 DOI: 10.1523/JNEUROSCI.1794-20.2021

Cite This Page:

University of California – Riverside. “Fruit fly offers lessons in good taste: Study shows food choice decisions require taste input.” ScienceDaily. ScienceDaily, 27 July 2021. <www.sciencedaily.com/releases/2021/07/210727171549.htm>.

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University Of São Paulo: The Conductor Of An Orchestra: Red-Rot Fungus Controls Insect And Plant To Spread

By Iednewsdesk On Jun 15, 2021Share

Infestations by pests and fungi in the sugarcane crop are one of the biggest problems faced by the sugar-alcohol industry and often occur together. Red rot, caused by the fungus Fusarium verticillioides, and the sugarcane borer, for example, are almost always in association. It was believed that the borer opened the way for the fungus to contaminate the sugarcane, but researchers at USP’s Luiz Queiroz School of Agriculture (Esalq) in Piracicaba, in an innovative discovery, point out that the relationship between the two is much closer than that it seems and the fungus is the master of this whole scheme.

Until then, it was understood that the fungus F. verticillioides was opportunistic, that is, it took advantage of holes made by the insect Diatraea saccharalis (sugarcane borer) in the cane stalks to infest the plant. However, the work Fungal phytopathogen modulates plant and insect responses to promote its dissemination , published in The ISME Journal, a journal of the International Society for Microbial Ecology published by the group Nature, revealed that this is not quite the truth. The result of seven years of research by the teams of professors Marcio de Castro Silva Filho, from the Laboratory ofMolecular Biology of Plants, and José Maurício Simões Bento, from the Laboratory of Chemical Ecology and Insect Behavior, both from Esalq, the study points out that the fungus F. verticillioides manipulates the borer and the plant in order to spread on the largest possible scale.

Relationship of the fungus with the sugarcane borer

All plants have natural defenses that resist different types of infestations and the fungus F. verticillioides cannot, by itself, infest sugarcane. He needs a facilitator to be able to contaminate it, since the healthy plant has in hand structural and biochemical mechanisms to resist the penetration of the fungus. In an environment where it is present, for example, but there is no borer, contamination of the sugarcane by the fungus is difficult.

Unlike other fungi, F. verticillioides has the advantage of an intimate interaction with the sugarcane borer, which allows its dispersion in a potentiated way. It produces volatile compounds that strongly attract D. saccharalis and when consumed, it infects the caterpillar and becomes part of its life cycle, remaining until the next generation, even in the absence of the fungus.

“As soon as the borer becomes an adult, like a moth, the fungus is transmitted to its descendants, who continue the cycle by inoculating the fungus into healthy plants”

This phenomenon is known as vertical transfer, a rare event in the biological realm and the first recorded case of a fungus-insect interaction. Professor Marcio de Castro Silva Filho, from the Genetics Department at Esalq and one of those responsible for this discovery, explains that “as soon as the borer becomes an adult, like a moth, the fungus is transmitted to its descendants, who continue the cycle by inoculating the fungus on healthy plants”.

In this way, the caterpillar becomes not a facilitator for the penetration of the fungus in the plant, as previously thought, but its own vector. One of the experiments in the study showed, for example, that when placing F. verticillioides and the caterpillar next to the sugarcane, its distribution throughout the plant is ten times greater than if the fungus were only using a mechanical perforation in the sugarcane.

The caterpillar, despite not having any direct benefit from this interaction, is also not harmed by its association with the fungus. The F. verticillioides remains in the drill throughout their life cycle without interfering, but he, in turn, is immensely benefited from this relationship.

Fungus-plant interaction

When infecting the plant, the fungus causes the cane stalk rot because it is a necrotrophic pathogen, that is, it destroys plant tissues through the release of toxins. The infestation causes a reduction in the sugar content and contamination of the sugarcane juice, which affects the quality and yield of the product. According to data from the Sugarcane Technology Center (CTC), the contamination of sugarcane fields by the association of the fungus with the insect causes annual losses in the range of R$ 5 billion, that is, around 400 thousand tons of sugarcane are not crushed per year.

In addition, the fungus alters the composition of the volatile compounds naturally produced by the plant to make it produce specific volatiles that attract healthy adult female borers. These, in turn, will ovipose uncontaminated plants in order to enhance the fungus’ dispersion. Professor at the Department of Entomology and Acarology at Esalq and also coordinator of the research, José Maurício Simões Bento, says that these volatiles “reduce the parasitism efficiency of the natural enemy of the sugarcane borer, the wasp Cotesia flavipes , making it difficult to biological control, because because the plant changes the composition of volatiles, the wasp has more difficulty in finding the caterpillar in the plantations”.

The way in which the fungus, aided by the borer, spreads in sugarcane fields reinforces the need for increased attention to biological control from the lowest infestations of the disease, in order to reduce as much as possible the population of the sugarcane borer, D. saccharalis, since it is the vector of the disease. For this, explains Professor Simões, “pest infestations should be kept, whenever possible, in low infestations, both by means of the larval parasitoid ( Cotesia flavipes ) and by the egg parasitoid ( Trichogramma galloi )”.

Fungus-plant-insect interaction

The fungus created a practically perfect strategy for its dissemination, in which it controls the insect in the caterpillar and adult (moth) stages, in addition to manipulating the plant, which makes it, in the words of Professor Castro Silva, the “great conductor of an orchestra”.

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Molecular Connections from Plants to Fungi to Ants

Lipids transfer energy and serve as an inter-kingdom communication tool in leaf-cutter ants’ fungal gardens.

22-Jun-2021 7:05 AM EDT, by Department of Energy, Office of Sciencefavorite_border

Newswise: Molecular Connections from Plants to Fungi to Ants

Illustration by Stephanie King, Pacific Northwest National Laboratory.

Nutrient-rich gongylidia in the center of leaf-cutter ants’ fungal gardens consist mainly of lipids that contain linoleic acid (18:2). Leaf material and the top of the garden consist mainly of lipids that contain alpha-linolenic acid (18:3).

The Science

Leaf-cutter ants tend gardens of fungi that efficiently deconstruct plant biomass. This process converts lipids in the leaves into lipids the ants can use. Lipids in these gardens are an energy source, a component of cells, and a chemical for communication between organisms. A multi-institutional team studied the variation in lipid content at the top, middle, and bottom regions of these fungal gardens. The three regions correspond to different stages of leaf degradation. The team also analyzed the lipids in the leaves that ants feed to the gardens and in nutrient-rich swellings called gongylidia that the fungi produce, and the ants eat. Using advanced chromatography and mass spectrometry techniques, the team found that the leaves and fungal garden components were enriched with different lipids.

The Impact

This study examines the role of lipids in the relationship between leaf-cutter ants and the fungi they cultivate. Both the ants and the fungi benefit, and the organisms co-evolved to create this symbiotic relationship. This study is the first global analysis of lipids in a symbiotic system. Understanding the lipid composition of ants’ fungal gardens provides new knowledge on communications between organisms in different kingdoms of life. It also advances the development of microbial systems that can produce useful compounds from plant biomass.

Summary

A team of scientists examined spatiotemporal changes in lipid content across six Atta leaf-cutter ants’ fungal gardens using advanced mass spectrometry technologies at the Environmental Molecular Sciences Laboratory, a Department of Energy (DOE) Office of Science user facility at Pacific Northwest National Laboratory. To understand which lipids existed initially, the scientists evaluated the lipid content of leaves that the ants feed to their fungal gardens. Then, they assessed the fungal gongylidia, as well as the top, middle, and bottom regions of the gardens at initial, intermediate, and advanced stages of leaf degradation, respectively. They compared the lipid content of the leaf material to the different regions of the fungal garden to track how the fungal cultivar consumed leaf lipids and synthesized its own lipids through the various regions. Leaf material at the top region of fungal gardens was enriched in alpha-linolenic acid (18:3). The team also compared the lipid content of the gongylidia to the middle region of the fungal garden to evaluate the hyphal swelling’s specific properties versus the area where the ants harvest it. Gongylidia was enriched in linoleic acid (18:2), which attracted the ants in a behavioral experiment. By restricting the enrichment of 18:2 lipids to the gongylidia, the fungus can focus the ants’ consumption to these specialized structures, thereby preventing damage to its growing filaments. This type of fungal metabolic regulation could be harnessed to develop microbial systems for sustainable bioproduct production.

Funding

This research was supported by an Early Career Research Program award to Kristin Burnum-Johnson and the DOE Great Lakes Bioenergy Research Center funded by the DOE Office of Science, Biological and Environmental Research program. The research was also supported by the USDA National Institute of Food and Agriculture, and the National Institutes of Health.

SEE ORIGINAL STUDY

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Joe Louis Studies the Molecular Battles Between Plants and Insects
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Joe Louis Studies the Molecular Battles Between Plants and Insects

The University of Nebraska–Lincoln entomologist wants to help pave the way for creating environmentally friendly tools to replace insecticides to control agricultural pests.

Shawna Williams
Mar 1, 2020

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ABOVE: © KATHY PLUNKETT PHOTOGRAPHY

It’s not easy to monitor electrical activity in an aphid. But it can be done with wire and glue. This electrical penetration graph technique involves gluing a wire onto an aphid’s back so that the insect is still able to walk around. When the animal is allowed to eat a plant conducting an electrical current, the resulting readout from the plant can provide valuable information about its feeding behavior. As an entomology master’s student at Kansas State University in the mid-2000s, Joe Louis set out to learn how to use the technique.

“He had to learn to apply the electronics and the technical side of that, which not many people have ever mastered,” says John Ruberson, who worked at Kansas State at the time and is now head of the entomology department at the University of Nebraska–Lincoln (UNL), where Louis is an associate professor. It might not have been obvious to others why Louis needed to go to the trouble, Ruberson explains, but mastering the technique would pay off.

When a wired aphid pricks its needle-like stylet into a plant conducting electricity, it completes an electrical circuit and generates a voltage spike in the readout from the wire. By using RNAi to block a gene’s product in insects and then employing their technique to monitor the feeding behavior, Louis was part of a team that figured out that a saliva protein in pea aphids (Acyrthosiphon pisum) called C002 is essential for the insects to feed on fava bean plants. It was the first aphid saliva protein identified.

After completing his master’s in 2006, Louis stayed at Kansas State to begin working toward a PhD with plant biologist Jyoti Shah, using the same electrical monitoring system in combination with molecular and biochemical approaches to study defenses the plant Arabidopsis thaliana deploys against hungry insects. Working with colleagues, they discovered an Arabidopsis gene, MPL1, that’s expressed in response to aphid infestation and is critical to the plant’s protection against the pests. While the exact mechanism wasn’t clear, the enzyme the gene codes for breaks down lipids, and appeared to limit the insects’ ability to reproduce, the researchers reported in 2010. Shah and Louis both moved to the University of North Texas in 2007.

Louis was “a go-getter,” Shah says. Rather than needing to be pushed to publish his work, for example, he would take the initiative to draft papers. “He was ambitious. . . . Even at that early stage of his career, he was quite independent with how he did things,” Shah recounts. “At the same time, he was open to advice.”

After earning his PhD from the University of North Texas, Louis went on to a postdoc with Gary Felton and Dawn Luthe at Pennsylvania State University before starting his own lab at UNL. There, he’s continued to delve into what he calls the “tug-of-war” between pest and plant. “We are trying to understand how plants can recognize those insects . . . so that they can rapidly and accurately activate . . . defenses,” he says. In a study published last year, he worked with graduate student Suresh Varsani and other colleagues to identify a chemical called 12-oxo-phytodienoic acid that is produced by aphid-resistant maize. The acid enhances the deposition of a protective polysaccharide called callose along the inside of cell walls, boosting the plant’s defenses. 

Ultimately, Louis hopes that findings like these will lead to innovative ways to protect crops from pests without harming the environment as today’s insecticides do. “This kind of research helps to [attain] a cleaner environment, and we can reduce the usage of these pesticides or chemical insecticides.” 

Shawna Williams is a senior editor at The Scientist. Email her at swilliams@the-scientist.com or follow her on Twitter @coloradan.

Keywords:

aphidsArabidopsiscropsecology & environmentelectricitygenetics & genomicsplant biologyplant defensesproteinScientist to watch

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