Molecular mechanisms underlying plant specialization in the pea aphid complex

Research

Context and Issues

Aphids are insect pests that feed on plant phloem sap and cause feeding damages and transmission of plant pathogens. The pea aphid (Acyrthosiphon pisum) complex is consisted of multiple biotypes each of which adapted to specific legume plants (e.g. clover, pea and medicago) and cannot perform well on non-adapted legumes. However, molecular mechanisms by which the aphids specialize to certain plant species are not yet understood. Aphids use a specialized mouth part to puncture plant phloem sieve cells and suck plant nutrients. During the feeding process, aphids secrete saliva which contains various proteins that might interact with plant proteins. Indeed, some aphid saliva proteins were shown to promote aphid colonization and some were shown to have negative impact. Another factor that is involved in plant-aphid interaction is facultative symbionts of aphids. Interestingly, the pea aphids carry various facultative symbionts and one of which, Regiella, is known to increase aphid adaptation to clover plants.  

Objectives

This project aims to examine the roles of aphid saliva proteins and aphid symbionts in host plant adaptation. Based on the numerous studies in plant-microbe interactions, we hypothesize that aphid salivary proteins function like microbial pathogen effectors (virulence and avirulence factors). Thus, we anticipate that the saliva proteins that are involved in host adaptation process are under high evolutionary pressure and/or show biotype specific expression patterns or polymorphisms. We further hypothesize that the presence of Regiella influences the composition of aphid saliva proteins and alter aphid-plant interactions

Methodology

In this fundamental research project, we will integrate transcriptional and genome resequencing data to identify the salivary genes that can be involved in the host plant adaptation processes of the pea aphid. Aphid gene silencing and in planta transient gene expression will be adapted and employed to examine the roles of the saliva genes in plant-aphid interactions. In addition, we will examine various Regiella strains that do/don’t increase aphid adaptation to clover to understand the complex host adaptation mechanisms of the aphids. We will conduct transcription analysis and saliva proteomics of the pea aphids with and without a selected Regiella strain to identify the factors that might be required to increase aphid performance on clover.

Perspectives

The project will develop tools to study legume-pea aphid interactions and advance our knowledge on the roles of aphid salivary proteins and their symbionts in host plant specialization process. This project is one of the first steps to develop benign strategies to control aphid pests in the field.

Funding and Support

ANR