Abstract: To clarify the effect of heat shock protein 90 (HSP90) on tolerance to high temperature in larvae of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), a full-length cDNA encoding HSP90 from S. exigua was cloned and characterized by RT-PCR and RACE technique. The complete cDNA (2 453 bp) contains a 2 154 bp open reading frame encoding 717 amino acid residues   (GenBank accession no. FJ862050). The complete amino acid sequence of HSP90 deduced from the cDNA consists of 25 residues for the putative signal peptide and 692 residues for the mature protein with the predicted molecular weight of 82.6 kD and the isoelectric point of 5.0, respectively, and carries an important and intact HSP90 signature sequence. The nucleotide sequence of the cDNA is highly similar with the HSP90 cDNA sequences of some other insect species. In order to explore the effects of HSP90 on tolerance to high temperature, a standard system was designed for real-time fluorescence quantitative RT-PCR, with which the relative expression of HSP90 gene at different instars of larvae in response to high temperatures was detected. The results indicated that high temperature induced the HSP90 expression obviously. Relative expression levels of HSP90 gene increased with the increase of temperature. The HSP90 expression levels in larvae of all tested instars under 43℃ and 45℃ were significantly higher than that under the normal temperature. However, the HSP90 expression levels in larvae of different instars were not significantly different. The results suggest that HSP90 may play an important role in high temperature tolerance in S. exigua.

Key words: Spodoptera exigua, HSP90, cDNA cloning, sequence analysis, real-time fluorescence quantitative RT-PCR, HSP90 expression