Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The right hitchhiker can save an aphid’s life

25.08.2005


Carrying the right bacterial hitchhiker can make the difference between life and death for an aphid.


A parasitoid wasp stalks pea aphids so she can lay eggs in them. The wasp is a tad bigger than 0.01 inches long. Photo credit: (c) 2005 Kerry M. Oliver.



Pea aphids are often under attack by wasps seeking to lay their eggs inside aphids, turning them into an all-you-can-eat buffet for the larval wasps.

The aphids vary in their resistance to the wasps, which scientists had chalked up to genetic differences between aphids.


But it’s not in their genes at all -- the wasp-resistant aphids owe their lives to the symbiotic bacteria carried inside them, according to new research.

"We knew there was a tremendous amount of variation in resistance to parasitism among different aphid lineages," said Kerry M. Oliver, lead author on the report. "We were definitely surprised – we assumed the bulk of the resistance was due to the aphids’ genotype."

Figuring out what makes insects resistant to natural enemies is important to farmers. Pea aphids can be agricultural pests on plants in the pea family including lentils and peas.

The new finding suggests why some lineages of aphids readily succumb to the wasps and others don’t.

"This work shows the difference can be attributed to the symbionts, not to the aphid genotype," said Oliver, a postdoctoral research associate in The University of Arizona’s department of entomology and a member of UA’s Center for Insect Science.

Oliver added that this implies aphids could acquire resistance to natural enemies by picking up bacterial symbionts, rather than having changes in the aphids’ genes. Such a newly acquired resistance is heritable, because the bacteria get passed down from mother to her offspring.

The article by Oliver and his co-authors Nancy A. Moran, UA Regents’ Professor of ecology and evolutionary biology, and Martha S. Hunter, UA associate professor of entomology, is published this week in the online early edition of the Proceedings of the National Academy of Sciences. The U.S. Department of Agriculture funded the research.

Many insects harbor bacterial symbionts that are passed from mother to offspring. LIttle is known about whether such symbionts can boost the host insects’ resistance to natural enemies.

As part of his doctoral research in UA’s Interdisciplinary Program in Insect Science, Oliver investigated the pea aphid, Acyrthosiphon pisum, an aphid known to vary in resistance to one of its major enemies, the parasitoid wasp Aphidius ervi. The aphids can also host one of several bacterial symbionts known as secondary symbionts.

One of his previous experiments indicated the symbiotic bacteria contribute at least some of the observed variation in resistance to the wasps.

"But we still thought most of the variation in resistance was due to the aphids’ genotype," he said.

To tease out how much of the resistance was from the aphids’ genes and how much from their symbionts, Oliver did another series of experiments. He took advantage of the fact that in the lab, aphids reproduce asexually -- female aphids produce more female aphids who produce more female aphids -- which means the offspring are identical genetically, generation after generation after generation.

Oliver injected several uninfected lineages of aphids with a secondary symbiont called Hamiltonella defensa. As a result, he had five genetically distinct colonies of pea aphids that all carried Hamiltonella defensa.

To test resistance to the wasps, he caged the different groups of infected aphids on individual fava bean plants by inverting plastic drink cups over the potted plants with aphids. Each plant had 30 aphids, all with the same bacteria inside.

Then he introduced a female wasp into each enclosure. Each wasp set about laying one egg per aphid in as many aphids as she could manage in the time allotted. Oliver removed the wasps after 6 hours.

Ten days later, he looked for evidence of wasp parasitism by counting the "mummies" -- the golden, hardened carcasses of aphids that had become homes for wasp larvae.

Oliver compared the rates of parasitism in uninfected aphids to infected aphids and found that carrying the H. defensa symbiont reduced parasitism by about 40 percent, no matter what the aphid’s genotype.

He also did another experiment by taking uninfected aphids and injected them with various different secondary symbionts, so he had five colonies of pea aphids that were genetically identical but harbored different bacteria.

In this case, the infected aphids varied from 19% to almost 100% resistance, depending on which symbiont they carried.

The experiments show that aphids’ variation in resistance to wasp parasitism stems from their bacteria, not their genes.

"Aphids are just completely nailed by natural enemies. Having these symbiotic defenders is really important to the aphids," Oliver said.

"Now we know symbionts confer resistance, but we don’t know the mechanism of resistance -- we don’t know the how." He said figuring that out is the team’s next step.

Mari N. Jensen | EurekAlert!
Further information:
http://www.arizona.edu

More articles from Life Sciences:

nachricht Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>