Abstract: 【Aim】 The study aims to analyze the expression difference of multicopper oxidase 4 gene and the biological effects after RNAi and feeding on different rice varieties in Sogatella furcifera, so as to provide a theoretical basis for fundamental function research of this gene. 【Methods】 The nucleotide and amino acid sequences of MCO4 gene were analyzed by bioinformatic methods. The MCO4 gene in the 3rd instar nymphs of S. furcifera was silenced by RNAi, the silencing efficiencies of microinjection method and feeding method were compared, and the effect of RNAi of MCO4 gene on the survival rate of the 3rd instar nymphs was studied. After feeding on rice varieties with different insect resistance for 24 h, the changes in the expression level of MCO4 in S. furcifera adults were detected by RT-qPCR, and their body weight was detected. 【Results】 The full-length cDNA of MCO4 gene is 2 166 bp, encoding 721 amino acids. RNAi by microinjection method successfully silenced the MCO4 gene of S. furcifera, with much higher silencing efficiency than that by feeding method. The survival rate of the 3rd instar nymphs with silenced MCO4 was significantly lower than that of the normal nymphs. Compared with the adults fed on the susceptible cultivar TN1, the adults fed on the resistant variety IR26 had significantly higher expression level of MCO4 and significantly reduced body weight. 【Conclusion】 Microinjection method can more efficiently silence the MCO4 gene of S. furcifera. Silence of MCO4 gene has significant effects on the survival rate of S. furcifera, and we speculate that MCO4 plays an important role in feeding of S. furcifera on rice.

Key words: Sogatella furcifera, saliva, multicopper oxidase 4, RNAi, microinjection method, feeding method