What are the mechanisms for maintaining the diversity of host races in the pea aphid?

Supervisors: Dr. Grit Kunert and Prof. Jonathan Gershenzon, Department of Biochemistry, MPI-CE; Dr. Alexandra Furch and Prof. Ralf Oelmüller, Plant Physiology, Friedrich Schiller University Jena

There are more species of herbivorous insects on our planet than almost any other group of animals outside of microbes. To explain this enormous proliferation of species, we are studying how insect herbivore species diversify by host plant shifting using the pea aphid ( Acyrthosiphon pisum ) as our model. This phloem-feeding herbivore consists of at least 11 distinct host races, each specialized on a different range of host plants of the legume family. Some aphid races are able to survive on a few plant species, while others survive on just one plant species. However, all pea aphid host races can develop on the broad bean, Vicia faba . This ecological specialization can be considered as one of the first steps towards sympatric speciation since the separation of races reduces gene flow among them.

We now wish to investigate the mechanisms that determine why pea aphid host races are able to feed on the phloem of some plants, but not others. Legumes regulate phloem mass flow with giant proteins called forisomes. Plants that recognize aphid attack might use forisomes to block the mass flow of phloem in sieve elements on which aphids are feeding. In addition, plants may employ hormones to trigger a variety of defensive responses, including the formation of metabolites toxic to aphids. On the other hand, aphids could strike back with saliva proteins that restore phloem mass flow and suppress defensive responses.

To explore these potential plant-aphid interactions, we will measure the phloem mass flow, forisome configuration, hormone levels and defense metabolites and genes in selected combinations of pea aphid host races and legume host plants. And, we will manipulate plant hormone signaling with transgenic approaches. On the insect side, we will analyze the saliva of various pea aphid host races and assess its protein degradation capacity. The results will establish the factors controlling the plant choice of pea aphid host races, and help understand what keeps the races separate.

The ideal candidate should have a background and experience in plant physiology, molecular biology, biochemistry or insect physiology. The project will provide excellent training in plant biochemistry, cell biology and microscopy, as well as molecular biology and analytical chemistry.

!!Application deadline is September 11, 2015!!

How to apply:
Please apply online at https://imprs-reg.ice.mpg.de
Send application to
The International Max Planck Research School (IMPRS)
Max-Planck-Institute for Chemical Ecology
Beutenberg Campus Hans-Knoell-Str. 8
D - 07745 Jena
You can also contact us via email: imprs2015@ice.mpg.de
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About International Max Planck Research School

In a joint initiative, the Max Planck Institute for Chemical Ecology, the Friedrich Schiller University, Jena, the Leibniz Institute for Natural Product Research and Infection Biology and the Leibniz Institute of Plant Genetics and Crop Plant Research are offering an international PhD program. This International Max Planck Research School (IMPRS) gives PhD students the possibility to prepare...

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