Abstract:  【Aim】 This study aims to determine the molecular characteristics of heat shock protein 70 (HSP70) genes in the small white butterfly, Pieris rapae and their response to insecticide stress, thus to pave the way for exploring the role of HSP70s in defense against insecticides in P. rapae. 【Methods】 Homology-basedsearchmethodwasusedtoidentifyHSP70 genes from the transcriptome dataset of P. rapae. Bioinformatic programs were used to analyze the molecular characteristics of these HSP70 genes. Real-time quantitative PCR was performed to determine the expression profiles of HSP70 genes at different developmental stages (2nd-5th instar larvae, pupae, and female and male adults), in different tissues of the 4th instar larvae (midgut, Malpighian tubules, fat body and integument) of P. rapae, and in the 4th instar larvae exposed to LD₂₀ of lambda-cyhalothrin (0.12 ng/μL) and chlorantraniliprole (1.04 ng/μL). 【Results】 Three HSP70 genes (PrHsp70-1, PrHsp70-2 and PrHsp70-3 with the GenBank accession numbers of MW691114, MW691115 and MW691116, respectively) were identified from the transcriptome of P. rapae. PrHSP70 proteins encoded by PrHsp70-1, PrHsp70-2 and PrHsp70-3 consist of 628, 630 and 653 amino acid residues, respectively, and have the molecular masses of 68.7, 69.2 and 71.7 kD, respectively. The results of bioinformatic analysis indicated that all of the three PrHSP70 proteins are localized within the cytosol and have the signature motifs of HSP70 family. PrHsp70-1 and PrHsp70-2 are intronless, whereas PrHsp70-3 contains an intron. The expression levels of PrHsp70-1 and PrHsp70-2 were upregulated along with the increase of larval instars and downregulated during pupal and adult stages. By contrast, the expression levels of PrHsp70-3 in P. rapae among different developmental stages showed no significant difference. PrHsp70-1 and PrHsp70-2 were highly expressed in larval fat body and midgut, respectively, while PrHsp70-3 displayed higher transcription level in both larval integument and fat body. Treatment with LD₂₀ of lambda-cyhalothrin and chlorantraniliprole caused significant upregulation of the three PrHsp70 genes, although their responses varied with time. Moreover, the transcription level of PrHsp70-3 was significantly downregulated at 24 h post exposure to LD₂₀ of lambda-cyhalothrin. 【Conclusion】 PrHsp70 genes may play essential roles in the growth and development and insecticide defense in P. rapae.

Key words: Pieris rapae, heat shock protein, sequence characteristics, expression pattern, lambda-cyhalothrin, chlorantraniliprole