Abstract: In order to study the function of ecdysone receptor in the diapause of Sitodiplosis mosellana, the full length cDNA sequence of an ecdysone receptor gene was amplified by using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE), and the expression of the EcR gene was analyzed using real-time quantitative PCR (qPCR). The full-length cDNA sequence was named as SmEcR (GenBank accession number: KC491135). Its open reading frame (ORF) is 1 386 bp in length, encoding a 461 amino acid protein, with a calculated molecular weight of 52.90 kD and the theoretical isoelectric point of 6.24. Multiple sequence alignment revealed that the deduced amino acid sequence of SmEcR has high identity with EcRs from other insect species, especially with that of Bradysia coprophila (92%). Real-time quantitative PCR showed that SmEcR transcripts were detected in all diapause and developmental stages. The expression of SmEcR was significantly different among different diapause stages, reaching the highest level in November and the lowest level in December. The larvae collected from wheat heads had a lower expression level of SmEcR while the adults had the highest SmEcR transcripts. This study lays the foundation for the further functional study of SmEcR in diapause regulation in S. mosellana.

Key words: Sitodiplosis mosellana, ecdysone receptor (EcR), gene cloning, diapause, expression analysis