Molecular characterization and expression profiling of ryanodine receptor gene in the pink stem borer, Sesamia inferens (Walker).

The susceptibilities of three field populations of pink stem borer (PSB), Sesamia inferens (walker) to diamide insecticides, chlorantraniliprole and flubendiamide, were evaluated in this study. The results showed that these PSB field populations were still sensitive to the two diamide insecticides after many years of exposure. To further understand PSB and diamide insecticide, the full-length ryanodine receptor (RyR) cDNA (named as SiRyR), the molecular target of diamide insecticides was cloned from PSB and characterized. The SiRyR gene contains an open reading frame of 15,420 nucleotides, encoding 5140 amino acid residues, which shares 77% to 98% sequence identity with RyR homologous of other insects. All hallmarks of RyR proteins are conserved in the SiRyR protein, including the conserved C-terminal domain with the consensus calcium-biding EF-hands (calcium-binding motif), the six transmembrane domains, as well as mannosyltransferase, IP3R and RyR (pfam02815) (MIR) domains. Real-time qPCR analysis revealed that the highest mRNA expression levels of SiRyR were observed in pupa and adults, especially in males. SiRyR was expressed at the highest level in thorax, and the lowest level in wing. The full genetic characterization of SiRyR could provide useful information for future functional expression studies and for discovery of new insecticides with selective insecticidal activity.

Monitoring and mechanisms of insecticide resistance in Chilo suppressalis (Lepidoptera: Crambidae), with special reference to diamides.

BACKGROUND: The rice stem borer, Chilo suppressalis Walker (Lepidoptera: Crambidae), is one of the most economically important pests of rice in Asia. Chemical control remains the most efficient primary means for controlling this pest. RESULTS: Significant variations among field populations in their resistance to seven insecticides were observed. The populations exhibited LC50 values that ranged between 0.605 and 108.088 mg AI L-1 for chlorantraniliprole and between 0.046 and 3.919 mg AI L-1 for flubendiamide. The YY14 population collected from Yuyao in Zhejiang Province in 2014 showed a moderate resistance level to the two diamides, i.e. up to 77.6-fold and 42.6-fold for chlorantraniliprole and flubendiamide respectively. Synergism tests and biochemical assays showed no obvious correlations between diamide resistance and three detoxifying enzymes. Sequence comparison of the ryanodine receptor gene between the YY14 resistant population and susceptible population revealed that a glycine to glutamic acid substitution (G4910E) was presented in the YY14 population. CONCLUSION: G4910E mutation might be involved in the resistance evolution of C. suppressalis to the diamides. An appropriate insecticide resistance management programme should be established to maintain the effectiveness of the insecticides and to ensure sustainable management. © 2016 Society of Chemical Industry.