Saturday, October 12, 2024

 

Red milkweed beetle genome offers insight into plant-insect interactions



Genome of host-specialist red milkweed beetle compared to generalist relative


University of Arkansas System Division of Agriculture

Mating pair of Red Milkweed Beetles 

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A mating pair of red milkweed beetles pictured in the spring of 2024 on the University of Arkansas campus in Fayetteville.

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Credit: U of A System Division of Agriculture photo by Rich Adams



FAYETTEVILLE, Ark. — Studying the secrets of how the common red milkweed beetle can safely feed on a toxic plant helps illuminate the ecological, evolutionary and economic impact of insect-plant interactions from a genomic perspective.

Although the relationship between the red milkweed beetle and milkweed plants has been studied for nearly 150 years, an Arkansas Agricultural Experiment Station scientist joined colleagues at the University of Memphis and the University of Wisconsin Oshkosh to do what no one else has done — curate the beetle’s genome and its arsenal of genes related to plant-feeding and other biological traits.

With support from the National Science Foundation, they sequenced and assembled the entire genome of the host-specialist milkweed beetle (Tetraopes tetrophthalmus). They then compared aspects of genome biology to a relative, the host-generalist Asian longhorned beetle (Anoplophora glabripennis), which is an invasive exotic species that feeds on a variety of trees important to forestry.

Their study, “Functional and evolutionary insights into chemosensation and specialized herbivory from the genome of the red milkweed beetle,” was published in the Journal of Heredity by the American Genetic Association this summer.

“From a biological standpoint, there is a lot of correspondence that suggests that longstanding interactions between milkweed beetles and their toxic milkweed hosts should influence the biology of both interacting partners,” said Rich Adams, a lead author of the study. “But, to date, no one had assembled a milkweed beetle genome, which opens the door for targeting a lot of interesting questions at the interface between insect and plant.”

Adams is an assistant professor of agricultural statistics in the department of entomology and plant pathology for the University of Arkansas System Division of Agriculture. He is also a member of the Center for Agricultural Data Analytics, a new initiative of the experiment station, and he teaches statistics courses in the Dale Bumpers College of Agricultural, Food and Life Sciences.

Scientific development

Milkweeds and milkweed beetles (genus Tetraopes) have been studied as valuable models for over a century of research into ecology, evolution, developmental biology, biochemistry of toxins and more, Adams said. They are also providing an interesting and compelling case of co-divergence patterns between insect and plant — meaning the plants and insects share similarities in the timing of co-evolution across their histories of interaction, Adams explained.

The research team showed that the red milkweed beetle has an apparent expansion of genes from the ABC transport family, which may help them feed on milkweeds and sequester its toxins inside beetle tissues. Milkweeds are renowned for their toxic latex cocktails, which affect the balance of sodium, calcium and potassium that keeps heart cells pumping. Adams said this genome provides insights into the genes the beetle has evolved to safely interact with its toxic milkweed hosts.

“Milkweeds produce a particularly nasty type of toxin called cardiac glycosides alongside other types of toxins that come with it,” Adams said. “For many insects that eat it, the toxin will block their sodium-potassium pumps. But this beetle developed a way to not only resist the toxin, but also sequester it, hold on to it, to keep the beetles themselves safe from would-be predators.”

The study also pinpointed differences in genes responsible for smell, taste and metabolic enzymes that degrade the plant cell well. Adams said it provides a new vantage point for exploring the ecology and evolution of specialized plant-feeding in longhorned beetlesand other plant-eating beetles.

Applications in agriculture, human health

These findings may help us understand and identify the genetic factors that shape agricultural and forestry pests and allow them to successfully feed on plants, as well as evade control efforts. Most animals that can digest woody plant material depend on microbes in their gut to break down plant cell walls; however, many plant-eating beetles do not.

Adams said many plant-feeding beetles, including longhorn beetles, acquired the ability to break down plant cell walls through horizontal gene transfers from microbes. By looking at the diversity of proteins encoded within beetle genomes, he said scientists can learn about the genomic basis of beetle biology, evolution and diversity, as well as their propensity for interactions with plants.

“Nature has made an incredible diversity of genes and genomes already out there that we have not yet deciphered,” Adams said. “Understanding this diversity holds great promise for informing agriculture, forestry and human health. Herbivorous beetles would have a difficult time feeding on plants without their metabolic enzymes, because they can’t eat effectively without them.”

In addition to studying the genomic DNA of the milkweed beetle, the team collected RNA from male and female red milkweed beetle antennae to learn more about how they seek out mates and food through chemosensation.

“Learning more about chemosensory biology — how an organism senses its environment, like sensing a host plant or reproductive partner — has broad relevance for understanding insect-plant interactions, which is intensively relevant to agriculture and forestry,” Adams said.

The RNA profile provided the first transcriptomic resource for Tetraopes. A transcriptome contains a range of genes that are transcribed into RNA molecules an organism expresses in a tissue or set of cells.

The DNA provides a gene sequence, the RNA offers “a better resolution of the gene and its expression, including how often the gene is getting made,” Adams explained.

Co-authors of the study included Terrence Sylvester (also a lead author) and Rongrong Shen, postdoctoral researchers at the University of Memphis with Duane D. McKenna, William Hill Professor in the department of biological sciences and director of the Center for Biodiversity; Matthew A. Price, formerly with the University of Wisconsin Oshkosh and now with the University of Hawaii at Manoa; and Robert F. Mitchell, formerly at the University of Wisconsin Oshkosh and now associate professor in the department of entomology at Pennsylvania State University.

The study was funded by National Science Foundation grants DEB-1355169 and DEB-2110053.

To learn more about the Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website. Follow us on X at @ArkAgResearch, subscribe to the Food, Farms and Forests podcast and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. Follow us on X at @AgInArk. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.

About the Division of Agriculture

The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.

The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on five system campuses.

The University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.

 

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European forest plants are migrating westwards, nitrogen main cause




German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig

Oxalis acetosella 

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The common wood sorrel (Oxalis acetosella) migrates westwards at a speed of around 5 kilometres per year and northwards at around 0.1 kilometres per year. The main driver is nitrogen deposition

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Credit: Petr Harant




New research reveals nitrogen pollution, and to a lesser extent climate change, unexpectedly as the key driver behind surprising westward shifts in the distribution of plants.

A recent study has uncovered that many European forest plant species are moving towards the west due to high nitrogen deposition levels, defying the common belief that climate change is the primary cause of species moving northward. This finding reshapes our understanding of how environmental factors, and in particular nitrogen pollution, influence biodiversity.

While it is widely assumed that rising temperatures are pushing many species toward cooler, northern areas, this research shows that westward movements are 2.6 times more likely than northward shifts. The primary driver? High levels of nitrogen deposition from atmospheric pollution, which allows a rapid spread of nitrogen-tolerating plant species from mainly Eastern Europe. The establishment of these highly competitive species in areas with high nitrogen deposition rates often comes at the expense of the more specialized plant species.

The results highlight that future biodiversity patterns are driven by complex interactions among multiple environmental changes, and not due to the exclusive effects of climate change alone. Understanding these complex interactions is critical for land managers and policymakers to protect biodiversity and ecosystem functioning.

Key findings:

  • European forest plants shift their distributions at an average velocity of 3.56 kilometer per year.
  • 39% of the plant species shift westward. Northward shifts are only observed for 15% of the species.
  • Nitrogen pollution rather than climate change is surprisingly the main factor behind westward distribution shifts in European forest plants.
  • The study analyzed the shifts in the distribution area of 266 forest plant species across Europe over several decades, with the first measurements being taken in the year 1933 at some locations.
  • Several of Europe’s most emblematic forests were included in this study, such as the primeval forest Białowieża in Poland.

This research was financed inter alia by the Deutsche Forschungsgemeinschaft (DFG; FZT-118). It is a product of the sDiv working group sREplot. iDiv’s synthesis centre sDiv supports working group meetings where international scientists work together on scientific issues.

 

Discovered by drones: World-first method reveals new plant species in endemic Hawaiian genus Schiedea



Pensoft Publishers
Drone collection of plant. 

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Drone collection of plant.

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Credit: Ben Nyberg, National Tropical Botanical Garden and Outreach Robotics





Schiedea waiahuluensis, a newly discovered species from Hawaii in the carnation family, is likely the first plant to be identified and collected using drone technology.

Researchers used drone photography to spot the unknown species growing on steep, inaccessible cliffs in the Waiahulu region of the island of Kauaʻi, in an area previously unexplored due to its extreme terrain.

This discovery, published in the open-access journal PhytoKeys, was made possible through the National Tropical Botanical Garden's (NTBG) botanical drone program, which deploys unmanned aircraft to explore remote cliff environments.

In collaboration with Quebec-based Outreach Robotics, NTBG developed ‘the Mamba,’ a remote plant collection device specifically designed for vertical cliff work. This device was suspended from a drone and used to grab, cut, and collect the plant for study.

The new species belongs to a well-studied Hawaiian lineage in the carnation family. Its genus, Schiedea, consists of 36 species spread across the Hawaiian Islands, with 12 species found only on Kauaʻi.

Schiedea waiahuluensis is found only on the dry cliffs of Waiahulu, with an estimated population of around 345 individuals, primarily growing on bare rock surfaces in small pockets of soil. The fragile habitat is under threat from invasive plant species and feral goats, making conservation efforts crucial. Further surveys are planned to assess the full distribution and conservation needs of the species.

Authors Stephen Weller and Ann Sakai from the University of California, Irvine note, “S. waiahuluensis has a combination of traits that would have been very difficult to predict, and upended our notions about diversity in Schiedea, even after decades of research on this genus.”

Lead author Warren Wagner, a research botanist at the Smithsonian Institution, states,“the new development of the NTBG drone program provides a major new tool in biodiversity research that has allowed for better assessment of species distribution and status as shown by drone missions on the inaccessible cliffs of the major canyons on Kauaʻi.

It has revealed populations of species presumed extinct such as the recent rediscovery of Hibiscadelphus woodii, a relative of Hibiscus, mapped populations of Schiedea waiahuluensis, and collected seeds via drone for establishment of a conservation collection of this species.”

This discovery, following more than 40 years of research on Schiedea on Kauaʻi, demonstrates the vast potential for future discoveries of native plants across the Hawaiian Islands through drone technology, and highlights the burgeoning role of drones in advancing conservation efforts and preventing plant extinctions.

Original study:

Wagner WL, Weller SG, Sakai AK, Nyberg B, Wood KR (2024) Schiedea waiahuluensis (Caryophyllaceae), an enigmatic new species from Kaua'i, Hawaiian Islands and the first species discovered by a drone collection system. PhytoKeys 247: 111-121. https://doi.org/10.3897/phytokeys.247.130241


Schiedea waiahuluensis habitat. A) Waiahulu branch of Waimea Canyon, drone photo. B) non-collected individual, drone photo.

 

Plants save energy when absorbing potassium




University of Würzburg

Potassium Uptake Systems of Plant Roots 

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Plants have two separate potassium uptake systems, the transporter HAK5 and the channel AKT1. Depending on the potassium concentration in the soil, one or the other system is responsible for the uptake of potassium into the roots. This ensures a constant supply of potassium even when potassium availability varies.

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Credit: Tobias Maierhofer / University of Wuerzburg




Potassium is one of the nutrients that plants need in large quantities. However, the amount of potassium in the soil can vary greatly: potassium-poor soils can contain up to a thousand times less of this nutrient than potassium-rich soils. To be able to react flexibly to these differences, plants have developed mechanisms with which they adapt their potassium uptake to the respective soil condition.

Like the cells of the human body, plant cells also work with an operating potassium concentration of around 100 millimolar. If the roots find a potassium source with a significantly lower concentration or only traces of it, they can only absorb the potassium into their cells by expending energy. This is achieved by the interaction between the potassium ion channel AKT1 and the potassium transporter HAK5.

Research is Relevant for Plant Breeding

‘Although HAK5 has been known since the late 1990s, its transport mechanism has so far remained largely unknown,’ says Professor Rainer Hedrich from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany. A team led by the Würzburg biophysicist now wanted to elucidate this mechanism: ‘Knowledge about this is important when it comes to breeding crops that also produce yields on non-fertilised or only lightly fertilised fields, i.e. that can manage with less fertiliser.’

In their experiments, the Würzburg research group led by first authors Tobias Maierhofer and Sönke Scherzer benefited from their extensive experience with the potassium channel AKT1. The group now describes their results in detail in the journal Nature Communications.

Establishing a pH Gradient Costs Energy

For the AKT1 channel to transport potassium into the cells, higher soil potassium concentrations are required. The normal electric field of the cell membrane is sufficient as an energy source. The HAK5 transporter, on the other hand, already works at low soil potassium levels. In addition to the electric field, it needs the energy of the pH gradient. The plant must build up this gradient across the cell membranes, and this costs energy.

Further experiments showed that the potassium transporter HAK5 and the potassium channel AKT1 co-operate in an energy-saving manner when the potassium concentration in the soil fluctuates.

Transporter Must Have a Potassium Sensor

At high concentrations, the energy-guzzling transporter HAK5 is switched off. This means that the transporter must have a potassium sensor. In their search for the sensor, the Frankfurt structural biologist Inga Hänelt and her Würzburg colleague Thomas Müller made progress: they found a mutant of the transporter in which the affinity for potassium is 100 times lower.

‘Now it is important to explore in more detail the molecular reactions that trigger the mutation,’ says Rainer Hedrich, describing the next research goals. He also wants to find out how potassium transport into the root cell is mechanically and energetically coupled to proton transport.