关键词: 麦红吸浆虫, Hsp60, 滞育, 温度胁迫, 基因表达, 分子伴侣

Abstract: 【Aim】The wheat blossom midge, Sitodiplosis mosellana, an important agricultural pest, survives under temperature extremes during summer and winter by diapause. This study aims to explore the relationship between heat shock protein 60 (Hsp60) gene expression and diapause development and temperature tolerance in the diapause process of S. mosellana.【Methods】 The full-length cDNA sequence of Hsp60 of S. mosellana (SmHsp60) was amplified via RACE and RT-PCR technologies, and analyzed via bioinformatics. qPCR was used to detect the expression levels of SmHsp60 in the S. mosellana larvae at different stages from pre-diapause to post-diapause development including pre-diapause, diapause, post-diapause quiescence and post-diapause development, as well as oversummering larvae under extremely high temperature stress ［exposed to water bathes at 34, 40, 45 and 50 ℃ for 1 h, and 35 ℃ for 0 (control), 15, 30, 60 and 120 min］ and overwintering larvae under extremely low temperature stress ［exposed to 0, -5, -10 and -15 ℃ for 1 h, and -5 ℃ for 0 (control), 15, 30, 60 and 120 min］. The recombinant SmHsp60 protein was obtained by prokaryotic expression and affinity column chromatography, and its ability to suppress the thermal aggregation of mitochondrial malate dehydrogenase (MDH) at 43 ℃ was examined by colorimetry and SDS-PAGE.【Results】 The full-length cDNA sequence of SmHsp60 (GenBank accession no: KR733065) of S. mosellana obtained is 2 270 bp in length, which contains an open reading frame (ORF) of 1 722 bp in length encoding a protein of 573 amino acids with the relative molecular weight of 60.7 kD. Amino acid sequence analysis indicated that SmHsp60 contains the classical signature sequences of mitochondrial Hsp60, and displayed the highest amino acid identity and the closest relationship to Hsp60 from Contarinia nasturtii of Cecidomyiidae. qPCR detection result showed that the expression level of SmHsp60 did not change significantly in the diapause stage, but began to increase gradually in the post-diapause quiescence stage with a peak in early-to-mid phase of post-diapause quiescence (i.e. December and next January) and was significantly higher than those in the other developmental stages. Compared to the untreated control, the expression of SmHsp60 in the oversummering larvae under 35 and 40 ℃for 1 h and 35 ℃ for 30-60 min and that in the overwintering larvae under -5 ℃ for 1 h was significantly induced, while the expression level of SmHsp60 did not change significantly above 45 ℃ or below -10 ℃. The highly purified recombinant SmHsp60 was able to effectively suppress the thermal aggregation of MDH, indicating its significant molecular chaperone function.【Conclusion】 SmHsp60 is involved in diapause regulation of S. mosellana and might play a role in diapause termination, as well as heat tolerance and cold tolerance during diapause.

Key words: Sitodiplosis mosellana, Hsp60, diapause, temperature stress, gene expression, molecular chaperone