Salivary gland transcriptome reveals bacterial symbionts of the potato leafhopper, Empoasca fabae

Many hemipterans are known to have symbiotic associations with bacteria. These bacterial symbionts provide their insect hosts with amino acids, vitamins and sometimes protection from pathogens or parasitoids. Most of the current knowledge of insect-symbiont interactions centers on the relationship between aphids and their primary symbiont Buchnera, and little is known about the symbionts of cicadellids. The salivary gland transcriptome of the potato leafhopper, Empoasca fabae, was recently sequenced using Roche 454-pyrosequencing to determine the identity of potential saliva constituents. Analysis of the transcriptome data revealed that 9% of the obtained sequences were bacterial in origin, with some of these bacterial sequences showing high similarity to species that behave as symbionts in other insect species. Primers designed to detect potential insect symbionts revealed by the transcriptome data were used to test for the presence of symbionts in the salivary glands, midgut, femurs and saliva of potato leafhoppers. RT-PCR expression analysis of potential symbiont genes also showed tissue-specific expression levels, indicating that symbionts are present in different numbers in the midgut and salivary glands. This is the first study to characterize the symbionts present in the potato leafhopper based on transcriptome data. Knowledge of the symbionts present in the tissues and saliva of this economically important agricultural pest may lend insight into the role that symbionts play in the hopperburn plant wound response caused by potato leafhopper feeding.