Grahame Jackson posted a new submission ‘A single laccase acts as a key component of environmental sensing in a broad host range fungal pathogen’

Saturday, 23 March 2024 08:16:28

PestNet

Submission

A single laccase acts as a key component of environmental sensing in a broad host range fungal pathogen

Nature

• Nathaniel M. Westrick, 
• Eddie G. Dominguez, 
• Madeline Bondy, 
• Christina M. Hull, 
• Damon L. Smith & 
• Mehdi Kabbage 

Communications Biology volume 7, Article number: 348 (2024) 

Abstract

Secreted laccases are important enzymes on a broad ecological scale for their role in mediating plant-microbe interactions, but within ascomycete fungi these enzymes have been primarily associated with melanin biosynthesis. In this study, a putatively secreted laccase, Sslac2, was characterized from the broad-host-range plant pathogen Sclerotinia sclerotiorum, which is largely unpigmented and is not dependent on melanogenesis for plant infection. Gene knockouts of Sslac2 demonstrate wide ranging developmental phenotypes and are functionally non-pathogenic. These mutants also displayed indiscriminate growth behaviors and enhanced biomass formation, seemingly as a result of their inability to respond to canonical environmental growth cues, a phenomenon further confirmed through chemical stress, physiological, and transcriptomic analyses. Transmission and scanning electron microscopy demonstrate apparent differences in extracellular matrix structure between WT and mutant strains that likely explain the inability of the mutants to respond to their environment. Targeting Sslac2 using host-induced gene silencing significantly improved resistance to S. sclerotiorum, suggesting that fungal laccases could be a valuable target of disease control. Collectively, we identified a laccase critical to the development and virulence of the broad-host-range pathogen S. sclerotiorum and propose a potentially novel role for fungal laccases in modulating environmental sensing.

Read on: https://www.nature.com/articles/s42003-024-06034-7

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Saturday, 23 March 2024 08:16:28

Grahame
Jackson posted a new submission ‘A single laccase acts as a key component of
environmental sensing in a broad host range fungal pathogen’

Submission

A single laccase acts as a key component of environmental sensing in a
broad host range fungal pathogen

Nature

• Nathaniel M. Westrick, 
• Eddie G. Dominguez, 
• Madeline Bondy, 
• Christina M. Hull, 
• Damon L. Smith & 
• Mehdi Kabbage 

Communications
Biology volume 7,
Article number: 348 (2024) 

Abstract

Secreted laccases are important enzymes on a broad ecological scale for
their role in mediating plant-microbe interactions, but within ascomycete fungi
these enzymes have been primarily associated with melanin biosynthesis. In this
study, a putatively secreted laccase, Sslac2, was characterized
from the broad-host-range plant pathogen Sclerotinia sclerotiorum,
which is largely unpigmented and is not dependent on melanogenesis for plant
infection. Gene knockouts of Sslac2 demonstrate wide ranging
developmental phenotypes and are functionally non-pathogenic. These mutants
also displayed indiscriminate growth behaviors and enhanced biomass formation,
seemingly as a result of their inability to respond to canonical environmental
growth cues, a phenomenon further confirmed through chemical stress,
physiological, and transcriptomic analyses. Transmission and scanning electron
microscopy demonstrate apparent differences in extracellular matrix structure
between WT and mutant strains that likely explain the inability of the mutants
to respond to their environment. Targeting Sslac2 using
host-induced gene silencing significantly improved resistance to S.
sclerotiorum, suggesting that fungal laccases could be a valuable target of
disease control. Collectively, we identified a laccase critical to the
development and virulence of the broad-host-range pathogen S.
sclerotiorum and propose a potentially novel role for fungal laccases
in modulating environmental sensing.

Read on: https://www.nature.com/articles/s42003-024-06034-7

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The genetic composition of fungi and its role in plant health

Exploring the genetic composition of fungi and its role in plant health

by University of Ottawa

Population analyses of R. irregularis. Credit: Nature Microbiology (2023). DOI: 10.1038/s41564-023-01495-8

The complex and very diverse world of fungi is often referred to as the fifth kingdom of organisms. It includes various yeasts, molds, and mushrooms. A team of scientists from the University of Ottawa (uOttawa) has uncovered the genetic secrets of a mysterious fungus, revealing the presence of two distinct nuclear populations within them, each playing distinct roles in how they interact with plants.

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Arbuscular mycorrhizal fungi (AMF) are tiny fungi that live in harmony with plants, sharing their genetic diversity and creating a vibrant atmosphere in plant roots and with below-ground microbes. Scientists have been studying AMF for years but are still puzzled by it. Its bodies are like bags packed with thousands of nuclei cells, and how these fungi cooperate with plants has long been unclear.

“There were numerous unresolved questions regarding AMF, mainly because these fungi are always multinucleated and do not exhibit observable sexual characteristics,” says Professor Nicolas Corradi, who holds the Chair in Microbial Genomics at the Department of Biology, University of Ottawa. “It has been proposed that AMF possess unique genetics and have undergone an unconventional evolution.”

Professor Corradi and colleagues investigated the asexual reproduction of AMF, specifically Rhizophagus irregularis. In 2016, they discovered strains that showed signs of sexual reproduction, with two populations of nuclei co-existing in large cells. “We found that strains having two populations (AMF heterokaryons) are more resilient and could access plant roots more easily, an indication they could be better bio-stimulants.”

However, without their complete genome, the researchers could not know why these strains are more successful plant symbionts.

Phylogenetic tree constructed with 65 R. irregularis strains. Haplotypes from AMF heterokaryons are shown in yellow squares. Based on relative branch lengths, the phylogeny resolves at least nine clades, which are highlighted in color. The tree was made using IQTREE algorithm, in GTR-FO mode with 1,000 bootstrap replicates. Scale bar represents 0.05 substitutions per site. When available, the MAT type of the strain is shown in parentheses. Note: the G1 strain located in clade VI noted with an asterisk is homokaryotic and does not represent the heterokaryotic isolate G1 (DAOM-970895) from clade IV. Credit: Nature Microbiology (2023). DOI: 10.1038/s41564-023-01495-8

To address this, Professor Corradi and his team employed advanced sequencing techniques, including RNA sequencing and third-generation DNA sequencing, to analyze differences in structure, content, and expression between the co-existing genomes.

“AMF heterokaryons have two haplotypes that physically separate among a large number, possibly millions, of co-existing nuclei. This phenomenon is unprecedented in any other organism,” explains Professor Corradi.

Their analyses also demonstrated that the two populations act very differently depending on their surrounding environment and their plant host. “Not only did we find that the two populations differ dramatically in the genes they harbor, but also that these are differently expressed and change in abundance depending on which plant they interact with,” adds Professor Corradi.

The symbiotic interactions between AMF and host plants are crucial for nutrient exchange, pathogen protection, and ecosystem sustainability. Studying these interactions will help improve agricultural practices by producing tailored biostimulants, enhancing plant growth, and promoting ecosystem health.

The study, titled “Arbuscular mycorrhizal fungi heterokaryons have two nuclear populations with distinct roles in host–plant interactions,” was published in Nature Microbiology.

More information: Jana Sperschneider et al, Arbuscular mycorrhizal fungi heterokaryons have two nuclear populations with distinct roles in host–plant interactions, Nature Microbiology (2023). DOI: 10.1038/s41564-023-01495-8

Journal information: Nature Microbiology 

Provided by University of Ottawa 

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In symbiosis: Plants control the genetics of microbes

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Double-stranded RNA prevents and cures infection by rust fungi

Friday, 08 December 2023 07:17:55

Grahame Jackson posted a new submission ‘Double-stranded RNA prevents and cures infection by rust fungi’

Submission

Double-stranded RNA prevents and cures infection by rust fungi

Nature

• Rebecca M. Degnan, 
• Louise S. Shuey, 
• Julian Radford-Smith, 
• Donald M. Gardiner, 
• Bernard J. Carroll, 
• Neena Mitter, 
• Alistair R. McTaggart & 
• Anne Sawyer 

Communications Biology volume 6, Article number: 1234 (2023) 

ABSTRACT
Fungal pathogens that impact perennial plants or natural ecosystems require management strategies beyond fungicides and breeding for resistance. Rust fungi, some of the most economically and environmentally important plant pathogens, have shown amenability to double-stranded RNA (dsRNA) mediated control. To date, dsRNA treatments have been applied prior to infection or together with the inoculum. Here we show that a dsRNA spray can effectively prevent and cure infection by Austropuccinia psidii (cause of myrtle rust) at different stages of the disease cycle. Significant reductions in disease coverage were observed in plants treated with dsRNA targeting essential fungal genes 48 h pre-infection through to 14 days post-infection. For curative treatments, improvements in plant health and photosynthetic capacity were seen 2–6 weeks post-infection. Two-photon microscopy suggests inhibitory activity of dsRNA on intercellular hyphae or haustoria. Our results show that dsRNA acts both preventively and curatively against myrtle rust disease, with treated plants recovering from severe infection. These findings have immediate potential in the management of the more than 10-year epidemic of myrtle rust in Australia.

Read on: https://www.nature.com/articles/s42003-023-05618-z

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New fungus is the oldest disease-causing species found to date

by Natural History Museum

Artistic rendition of the Rhynie Chert in the Early Devonian period. Credit: Victor O. Leshyk

The earliest disease-causing fungus has been discovered within the Natural History Museum’s fossil collections. The new fungal plant pathogen, Potteromyces asteroxylicola, which is 407-million-years-old, has been named in honor of celebrated Tales of Peter Rabbit author, and fungi enthusiast, Beatrix Potter.

The paper, “A fungal plant pathogen discovered in the Devonian Rhynie Chert,” has been published in Nature Communications

Beatrix’s drawings and study of the growth of fungi, which were in some cases decades ahead of scientific research, have garnered her a reputation as a significant figure in mycology.

Potteromyces was discovered in fossil samples from the Rhynie Chert, a crucial geological site in Scotland. The site is known for a remarkably preserved Early Devonian community of plants and animals, including bacteria and fungi.

The new study, completed in collaboration with mycologists at the Royal Botanic Gardens, Kew, suggests that disease-causing fungi, such as ash die-back currently decimating the UK’s native ash trees, and fungi which can circulate nutrients that plants and other organisms depend on to survive, have a historical precedent in Potteromyces.

Dr. Christine Strullu-Derrien, Scientific Associate at the Natural History Museum and lead author of the study describing the new species, says, “Although other fungal parasites have been found in this area before, this is the first case of one causing disease in a plant. What’s more, Potteromyces can provide a valuable point from which to date the evolution of different fungus groups, such as Ascomycota, the largest fungal phylum.”

“Naming this important species after Beatrix Potter seems a fitting tribute to her remarkable work and commitment to piecing together the secrets of fungi.”

Christine found the first Potteromyces specimen in 2015. Its reproductive structures, known as conidiophores, had an unusual shape and formation unlike anything seen before.

Equally unusual was the fact this mysterious fungus was found attacking an ancient plant called Asteroxylon mackiei. The plant had responded by developing dome-shaped growths, showing that it must have been alive while the fungus making its attack.

In order for the team to determine that it was indeed a new species, another case of the fungus needed to be found. This is due to the nature of fungi differing greatly between individuals.

The confirmation was achieved when a second specimen was found in the collections of the National Museums of Scotland in another specimen slide from the Rhynie Chert.

“New technology available to us, such as confocal microscopy, has enabled us to unlock more secrets from fossils housed in museum collections, such as those within the Natural History Museum,” said Christine.

“When I first started work on the Rhynie Chert, it was only meant to take two or three years,” Christine says, “It’s now been 12, and I still think there is a lot to discover from this fabulous site.

More information: Christine Strullu-Derrien et al, A fungal plant pathogen discovered in the Devonian Rhynie Chert, Nature Communications (2023). DOI: 10.1038/s41467-023-43276-1

Journal information: Nature Communications 

Provided by Natural History Museum 

This story is republished courtesy of Natural History Museum. Read the original story here

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Ancient bacteria species among the first of its kind to colonize land

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The future of agriculture may be too small to see. Think microbes

PRI’s The World
Reporter Cynthia Graber
July 02, 2014 · 2:15 PM EDT

http://www.pri.org/stories/2014-07-02/future-agriculture-may-be-too-small-see-think-microbes

Thin filaments of fungi form a dense network between the roots of most of the world’s food crops. Some researchers believe that working with such microbes rather than against them, as has often been the case in conventional agriculture, will help the world grow more food with less environmental impact.

 

 

 

Geneticist Ian Sanders and his colleagues grew cassava in this field in Colombia using a fungal gel that he says improved yields by 20 percent. Cassava, which is native to Colombia, is one of the world’s most important food crops, feeding over a billion people.

 

Thin filaments of fungi form a dense network between the roots of most of the world’s food crops. Some researchers believe that working with such microbes rather than against them, as has often been the case in conventional agriculture, will help the world grow more food with less environmental impact.

Stick a shovel in the ground and you’ll dig up some soil, maybe a few little rocks and, of course, some roots.

Now — take those roots inside for a closer look and you’ll see something else as well.

“When you hold this thing up to the light, what you can see is little tiny filaments,” says geneticist Ian Sanders, holding up a root in his lab at the University of Lausanne in Switzerland.

The filaments look like tiny strands of cotton..

“That’s the fungus,” says Sanders.

Sanders is obsessed with fungi, because he thinks they can play a big role in solving the world’s big food challenges in a time of rapid climate change and population growth.

In particular, Sanders is obsessed with a type of fungi that live on the roots of about 80 percent of the plants on the planet. Their tiny filaments help plants grow by drawing water and nutrients to the plant. In return, the plants feed sugars to the fungi.

It’s a symbiotic relationship that Sanders says is incredibly important.

“Almost all our food plants naturally form this association with these fungi,” he says.

And these species of fungi aren’t alone. There are thousands, maybe millions of kinds of fungi, bacteria and other microbes that help plants in a variety of ways.

But their role has been almost invisible to people. In fact, critics say, modern agriculture actively works against them.

“What we’ve done over the last hundred years in agriculture, is to try to take microorganisms out of the picture,” says Seattle microbiologist Rusty Rodriguez.

“And by doing that, by disrupting the soil with tillage, by using chemical pesticides, we have greatly altered the agricultural microbiome.”

Rodriguez is also obsessed with fungi. And like Sanders, he wants to re-alter the agricultural mircobiome. Both are part of a growing field of researchers and entrepreneurs working to bring microorganisms like fungi back into the agricultural mix, but in a new and targeted way. Sanders is breeding new varieties in the lab, while Rodriguez’s company gathers fungi from extreme environments all over the US and cultivates them in their lab and greenhouse in Seattle.

Right now, Rodriguez is using the fungi to help grow tomatoes, soybeans and corn. His hope is that the microbes will help crops like these survive growing climate stresses like droughts and floods and extreme heat and cold.

Rodriguez is working with different kinds of fungi than Sanders. His grow throughout the plant, not just on roots. But his goal is the same — to find and develop fungi that make agriculture both more productive and more sustainable. And, he says, his first two products using these microbes are just about ready for prime time, with a possible launch later this year.

Sanders’s work isn’t quite there yet. He and his colleagues are still conducting field tests in places like Colombia. But he says the results so far have been very promising.

Columbia is home to cassava, a root crop that feeds more than a billion people around the world. Sanders and a group of Colombian researchers set up experimental plots there to grow cassava using a new fungal gel that they hoped would significant increase yields while significantly reducing fertilizer use.

When they harvested their first crop a year later, Sanders says, they were “delighted” by the results — the plants had grown up to 20 percent more roots.

Sanders says the result actually surprised him, but that it was just the beginning. The research team has since grown cassava with different varieties of lab-bred fungi, and so far, he says, the impact has been even more dramatic.

Rodriguez, in Seattle, shares Sanders’s bullish view of the future of agricultural fungi and bacteria.

“Biologics,” he believes, “are the next paradigm for agriculture.”

Of course we’ve heard talk like that before. Think chemical pesticides, synthetic fertilizers and GMOs, all of which brought big initial benefits, but also big environmental problems, or at least big concerns.

So far, there hasn’t been much push-back on biologics from environmentalists, but just because something’s natural doesn’t mean it’s safe. Which is why both Sanders and Rodriguez say they’re working to make sure the fungi they’re developing won’t bring any unwanted impacts.

“You have to know the organism is safe,” Rodriquez says. “I never want to be in a situation where I stand up in front of an audience and they ask me that question and I say ‘I don’t know.’”

What Rodriguez does know is that lots of tools will be needed to help produce more food, more sustainably.

And Sanders says we’ve been standing on some of those tools all along.

“Sometimes people think you have to go to unexplored wilderness to find something completely new,” Sanders says. “But we just have to look in the soil that’s beneath our feet.”

 

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