Combined transcriptomic/proteomic analysis of salivary gland and secreted saliva in three planthopper species.

The planthoppers are piercing-sucking pests that continuously inject saliva into host plants using specialized stylets. However, knowledge on the constituent and function of planthopper saliva proteins was still limited. In this study, the transcriptomic and proteomic approach were adopted to characterize the composition of salivary glands and their secreted saliva in three planthoppers, respectively. Gene repertoires of salivary glands in brown planthopper (Nilaparvata lugens, BPH), white-backed planthopper (Sogatella furcifera, WBPH) and small brown planthopper (Laodelphax striatellus, SBPH) were very similar, which actively involved in protein synthesis and energy metabolism. Comparative analysis of saliva proteome was performed among three planthoppers and other reported insect species. The saliva composition in three planthoppers was diverse, with 55 saliva proteins commonly identified in more than two species. A few proteins, including serine protease, carboxylesterase, aminopeptidase N, lipophorin, elongation factor, carbonic anhydrase, and calcium binding protein were ubiquitous distributed in different insects, indicating conserved function of saliva. While, the majority of saliva proteins were specifically identified in planthoppers, which might be the evolutional adaptation of insects to different hosts. Our work gained insight into the interaction between insect and host plant through salivary approach, and provided a good resource for functional characterization of effectors.

BIOLOGICAL SIGNIFICANCE: Secreted saliva from insects is attracting immense research interest on the global level due to the crucial roles in determining the compatibility between the insects and their hosts. The three planthoppers: brown planthopper (Nilaparvata lugens, BPH), small brown planthopper (Laodelphax striatellus, SBPH), and white-backed planthopper (Sogatella furcifera, WBPH) caused serious damage to rice plants throughout Asia. However, knowledge on the composition and function of their secreted saliva proteins was limited. Our study characterizes the global gene expression of salivary glands and their secreted saliva by Illumina sequencing technology and LC-MS/MS analysis, respectively. By comparative analysis, the ubiquitous and specific saliva compounds in different insects were unveiled.