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  The influence of Regiella insecticola on legume plant – pea aphid interactions


   International Max Planck Research School

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  Dr Grit Kunert, Prof Jonathan Gershenzon, Prof Martin Kaltenpoth, Dr Alexandra Furch  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

About the Project

Background:

Insects have established many mutualistic associations with microbes. Herbivorous insects harbor a large diversity of endosymbiotic bacteria that influence insect growth, development and survival. However, how these bacteria actually change insect performance is not fully understood. Endosymbionts supplement essential nutrients in the insect diet and degrade plant defense compounds, but might also influence how plants react to herbivore attacks.

In our research group, we have long used the pea aphid (Acyrthosiphon pisum) as a model for investigating speciation. The pea aphid comprises at least 15 distinct biotypes, each specialized on one or a few host plant species of the legume family. The phloem sap ingested by aphids, while rich in carbohydrates, is deficient in many nitrogen-containing compounds. To compensate for this nutritional deficiency, all aphids contain the obligatory bacterial endosymbiont, Buchnera aphidicola, which provides essential amino acids. In addition, many aphids harbor other bacteria as facultative endosymbionts, such as strains of Regiella, Serratia, and Rickettsia. Their biological roles are much less clear than those of the obligatory endosymbiont. We found that Regiella insecticola influences the performance of pea aphids on some of their host plants. We now aim to explore how R. insecticola triggers such changes in insect performance.

Project description:

R. insecticola might influence pea aphid performance either indirectly via changes in the plant or directly via changes inside the aphid. To test the first hypothesis, we want to investigate whether aphids with and without the facultative endosymbiont R. insecticola elicit a different defense reaction in plants.

One way plants recognize aphids is via herbivore associated molecular patterns, like peptides and proteins present in the aphid saliva and injected into plants whilst aphids are feeding. Therefore, we will investigate whether and how R. insecticola might change the saliva composition.

Aphid saliva not only allows the plant to recognize aphids, but components of the saliva might also help aphids to overcome plant defense responses. Calcium-scavenging proteins present in the saliva might suppress the plant’s early defense reaction. Therefore, we plan to investigate whether saliva from aphids with and without R. insecticola differs in its calcium-scavenging capacity.

Additionally, we want to investigate whether R. insecticola directly changes the metabolome of the aphids. Special interest lies in lipid metabolism, amino acid composition and the fate of plant derived defense compounds.

Candidate profile:

We are looking for a PhD student motivated to work in an interdisciplinary way in the fields of microbiology, insect and plant physiology and biochemistry. Prior knowledge in at least two of these fields would be of great advantage.

Biological Sciences (4)

 About the Project