How do insects survive on a sugary diet?

May 25, 2018 by Sarah Nightingale, University of California - Riverside
How do insects survive on a sugary diet?
UC Riverside researchers are the first to show that DNA methylation patterns in symbiotic aphid cells are related to host plant diet. Credit: Daniel Villafruela

There's a reason parents tell their kids to lay off the sugar: too much isn't good for you.

But small sap-sucking insects called aphids can survive quite nicely on a largely sugar-based diet, despite their inability to make important nutrients from scratch. The key to their success is , which live inside aphid cells and make amino acids, the building blocks of proteins needed for growth.

In research published in G3: Genes, Genomes, Genetics, researchers at the University of California, Riverside, show that bacteriocytes—specific aphid cells that house the symbiotic —have different DNA methylation patterns depending on what type of plant sap the aphid is consuming.

DNA methylation is a way of regulating that doesn't involve changes to the DNA sequence itself, meaning can be turned "on" or "off" depending on environmental factors. The study is the first to show that DNA methylation patterns in symbiotic insect cells are related to host plant diet.

Allison Hansen, an assistant professor of entomology at UCR, said the differences in DNA methylation and resulting changes in gene expression point to shared metabolic pathways between the aphid and its symbiotic bacteria. By changing gene expression, the aphid can make sure the bacteria have the ingredients they need to produce essential nutrients from a sugar-rich diet.

"This study provides interesting insight into the close relationship that aphids have developed with their symbiotic bacteria as they have co-evolved together for approximately 150-200 million years," Hansen said. "DNA methylation of bacteriocytes likely enables the aphids to work together with their resident bacteria to survive, especially when they switch to a plant sap that is not rich in nutrients."

Hansen and Dohyup Kim, a doctoral student in UCR's entomology department and lead author on the paper, analyzed one of the largest DNA methylation datasets for insects that rely on nutritional symbionts. The pair used a model insect-microbe system comprising pea aphids and the bacterium Buchnera.

The researchers found that key aphid genes involved in nutritional symbiosis were activated in bacteriocytes—the cells housing the bacteria—in low-nutrient diets. One of these genes is for a protein that recycles ammonia into glutamine, an essential ingredient needed by the bacteria in sustaining aphids on a nitrogen-limited diet. Another gene codes for a protein that transports glutamine into bacteriocytes, where it can be used by the bacteria.

"In long-term, co-evolved animal-microbe relationships, many microbes form shared metabolic pathways with their animal hosts, but how these processes are reciprocally regulated has remained a mystery," Hansen said. "Our research points to epigenetic gene regulation through DNA methylation as one way to induce this regulatory response. However, more work is needed to fully understand our observations."

The title of the paper is "Key Transport and Ammonia Recycling Gene Involved in Aphid Symbiosis Respond to Host-Plant Specialization."

Explore further: Researchers discover a 'simple and elegant mechanism' that regulates relationships between insects, bacteria

More information: Dohyup Kim et al. Key Transport and Ammonia Recycling Genes Involved in Aphid Symbiosis Respond to Host-Plant Specialization, G3: Genes, Genomes, Genetics (2018). DOI: 10.1534/g3.118.200297

Related Stories

Researchers discover a 'simple and elegant mechanism' that regulates relationships between insects, bacteria

May 5, 2014
Symbiosis is the process that occurs when two different organisms live together to form a mutually beneficial partnership. In many symbiotic relationships, host animals and their microbial symbionts are partners that make ...

Recommended for you

Critical role of DHA on foetal brain development revealed

August 17, 2018
Duke-NUS researchers have found evidence that a natural form of Docosahexaenoic Acid (DHA) made by the liver called Lyso-Phosphatidyl-Choline (LPC-DHA), is critical for normal foetal and infant brain development, and that ...

New algorithm could improve diagnosis of rare diseases

August 17, 2018
Today, diagnosing rare genetic diseases requires a slow process of educated guesswork. Gill Bejerano, Ph.D., associate professor of developmental biology and of computer science at Stanford, is working to speed it up.

Gene silencing critical for normal breast development

August 17, 2018
Researchers have discovered that normal breast development relies on a genetic 'brake', a protein complex that keeps swathes of genes silenced.

Officials remove special rules for gene therapy experiments

August 16, 2018
U.S. health officials are eliminating special regulations for gene therapy experiments, saying that what was once exotic science is quickly becoming an established form of medical care with no extraordinary risks.

Genetic link discovered between circadian rhythms and mood disorders

August 15, 2018
Circadian rhythms are regular 24-hour variations in behaviour and activity that control many aspects of our lives, from hormone levels to sleeping and eating habits.

Ovarian cancer genetics unravelled

August 14, 2018
Patterns of genetic mutation in ovarian cancer are helping make sense of the disease, and could be used to personalise treatment in future.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet May 25, 2018
Don't most insects die in a few days?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.