SRA

Background Aphids cause a substantial amount of damage and therefore yield loss to world-wide agriculture. Aphids interact with their hosts at a molecular level using molecules secreted in their saliva (effectorss). In this study we used a multi-disciplinary approach of RNA sequencing of dissected aphid material and LC-MS analysis of aphid saliva in order to identify effector candidates from generalist Myzus persicae (genotypes O, J and F), a specialist species M. cerasi and the cereal specialist Rhopalosiphum padi. Results Proteomic analysis of aphid saliva identified a total of 204 proteins. RNA sequencing and the use of differential expression analysis between heads (contains salivary glands) and bodies (without nymphs and without heads) identified transcripts which were upregulated in “heads”, those encoding signal peptides and no transmembrane domain were considered putative effectors. The majority of candidate effectors had sequences with high similarity only to other aphid sequences, indicating aphid specific evolution. De novo transcriptomes were subjected to comparative analysis to identify conserved/core aphid effectors and putative pioneer effectors. The “conserved” effectors consisted of a number of sequences predicted to be involved in the detoxification of plant defence responses and previously identified effector candidates (Bos et al., 2010), including 50 hypothetical Acyrthosiphon pisum salivary gland sequences (Carolan et al., 2011). Several of these sequences were identified as being under positive selection pressure, including previously identified Macrosiphum euphorbiae effector Me10 (Atamian et al., 2013) which was also within the top 120 expressing transcripts in all species. 43 putative pioneer effectors were identified, some of which may be species or genus specific. Conclusion A combined proteomic and bioinformatic approach identified putative effectors from three species of aphids. Clustering analysis was used to identify conserved groups of putative effectors that may be a per-requisite for plant-aphid interactions.