The Identification Of Saliva Protein And Preliminary Analysis Of These Genes In Nilaparvata Lugens

The brown planthopper (Nilaparvata lugens) is the most destructive pest of rice and causes serious economic damage in Asia. Saliva plays the crucial roles in the interaction between the insects and their plant hosts during feeding process. Studying of N. lugens saliva is significant to understand the mechanism how this insect damage rice and establish efficient of pest control strategies. Totally twenty-four thousand insect individuals were used to collect saliva by means of feeding with artificial diet solution. We identified 206 saliva proteins using shotgun proteomic analysis and found their corresponding genes against genome searching. Twelve genes were selected for further investigation using quantitative real-time PCR and RNA interference. The developmental stage expression patterns showed that 9 genes had higher expression in males when compared to the females. The tissue specific expression patterns showed that 8 genes displayed the highest expressions in salivary gland, and 6 genes exclusively expressed in salivary gland. RNAi suggested that one gene, called NICaM had the significant lethel phenotype. The open reading frame gene (ORF) of NICaM is 450bp in length, which is potential to encode a predicted 16.4kDa protein, with two EF-hand domains and containing 149 amino acid residues. Quantitative RT-PCR showed that NICaM expressed highest in salivary gland, and no significant difference in the various developmental stages except higher in males. RNAi showed that silencing of NICaM resulted in the abnormal phenotype with blacker body and curled wings, developmental duration extending and mortality rate of 100%. Moreover, the assay of honeydew excretion indicated that the amount of food intake was reduced; the electrical penetration graph (EPG) results showed that it became difficult for N. lugens 5th instar nymphs to ingest xylem and phloem sap. These findings suggested that NICaM plays an essential role both in the feeding process and the physiological and biochemical metabolism.