Ryanodine receptor genes of the rice stem borer, Chilo suppressalis: Molecular cloning, alternative splicing and expression profiling

- New Chilo suppressalis RyR alternative splicing site and two encoding genes
- RyR amino acid sequence KENLG is found only in Lepidoptera.
- Chlorantraniliprole injection greatly increases larval RyR mRNA expression levels.
- RyR phylogenetic diversity contributes to diamide insecticide selectivity.

The ryanodine receptor (RyR) of the calcium release channel is the main target of anthranilic and phthalic diamide insecticides which have high selective insecticidal activity relative to mammalian toxicity. In this study, the full-length cDNA of Chilo suppressalis RyR (CsRyR) was isolated and characterized. The CsRyR mRNA has an open reading frame (ORF) of 15,387 bp nucleotides, which encodes 5128 amino acids with GenBank ID: KR088972. Comparison of protein sequences showed that CsRyR shared high identities with other insects of 77-96% and lower identity to mammals and nematodes with only 42-45%. One alternative splicing site (KENLG) unique to Lepidoptera was found and two exclusive exons of CsRyR (I /II) were revealed. Spatial and temporal expression of CsRyR mRNA was at the highest relative level in 3rd instar larvae and head (including brain and muscle), and at the lowest expression level in egg and fat body. The expression levels of whole body CsRyR mRNA were increased remarkably after injection of 4th instar larvae with chlorantraniliprole at 0.004 to 0.4 μg/g. This structural and functional information on CsRyR provides the basis for further understanding the selective action of chlorantraniliprole and possibly other diamide insecticides.

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