Cloning And Sequencing Of Partial Sodium Channel Gene From Helicoverpa Assulta And Spodoptera Exigua

Using polymerase chain reaction (PCR), 250bp fragment of the sodium channel gene from resistant and sensitive populations of Helicoverpa assulta and natural populations of Spodoptera exigua were cloned and sequenced, then compared the nucleotide and amino acid sequences from each other. The purpose of this study is to investigate whether the knockdown resistance (kdr) is involved in the resistance to pyrethroid of Helicoverpa assulta and natural populations of Spodoptera exigua.It is suggested that the nucleotide homology between the resistant and sensitive populations of Helicoverpa assulta is 89.62%, and the amino acid sequences homology is 100%. The amino acid in IIS6 1014 site in resistant and sensitive populations are both with Leu (CTT), therefore, the kdr is not involved in the resistant strains of Helicoverpa assulta.The sequenced nucleotide homology between the natural populations Spodoptera exigua and the resistant populations of Helicoverpa assulta is 89.62%, and that between the natural populations Spodoptera exigua and the sensitive populations of Helicoverpa assulta is 98.91%. The amino acid sequences homologies between them are both 98.36%. The amino acid in II S6 1014 site is Phe not Leu, that is to say, there is a point mutation in the resistant populations of Spodoptera exigua. It is suggested that the kdr is involved in the natural populations of Spodoptera exigua.The sequenced nucleotide homology of II S6 sequences among Lepidoptera insects are all above 88%. But the nucleotide homology of II S6 sequences between Lepidoptera insects and D.melanogaster of Diptera is about 80%, and that between Lepidoptera insects and German cockroach of Blattodea is about 70%. The sequenced nucleotide homology of II S6 sequences between D.melanogaster of Diptera andGerman cockroach of Blattodea was 71.43%.It was suggested that the nucleotide homology of IIS6 sequences was higher in the same order insects than in the different order insects.The amino acid homology of IIS6 sequences between the sensitive populations of Helicoverpa assulta and the sensitive populations of para, CPIk PA-HL, Copper and Hpkl are all 100%. IIS6 sequences were highly conservative in different sensitive insects populations. It is easy to identity the point mutation among sodium channel gene of pyrethroid-resistant populations of insects.The amino acid identity of IIS6 sequences between Helicoverpa assulta and para from D.melanogaster is 100%?between Spodoptera exigua and para from D.melanogaster is 96.43%. The amino acid identity of II S6 sequences between Helicoverpa assulta and DSCl from D.melanogaster is only 60.71%, between Spodoptera exigua and DSCl is only 64.28%. Therefore, the amplified sequences are all para homofogy.This study provided the theoretical basis for the resistance forecast and management of Helicoverpa assulta and Spodoptera exigua populations.