Abstract:  【Aim】 This study aims to screen the key genes in the selenium metabolism pathway of Tetranychus cinnabarinus and to explore their functions in selenium metabolism in T. cinnabarinus. 【Methods】 The gene cloning technology was used to clone eight genes in the selenium metabolism pathway of T. cinnabarinus. The differences in the expression levels of these genes in female adults of the short-term selenium-reared strain of T. cinnabarinus with different concentrations of Na₂SeO₃ (fed with cowpea seedlings treated with 0, 5, 20 and 50 μmol/L Na₂SeO₃ for 3 d), and in female adults of the normal strain (fed with cowpea seedlings) and the long-term selenium-reared strain (fed with cowpea seedlings treated with 20 μmol/L Na₂SeO₃ for over one year) were detected by qPCR, and the expression responses of these genes to selenium induction were analyzed. Finally, the prokaryotic expression system was used to express one differentially expressed gene TcSPS1, and the biochemical characteristics of the obtained recombinant protein were assayed. 【Results】 Eight selenium metabolism pathway genes of T. cinnabarinus were successfully cloned, including TcTxnrd1, TcTxnrd2, TcSPS1, TcSPS2, TcSPS2-1, TcSPS2-2, TcSG, and TcPSTK. qPCR results showed that only TcSPS1 and TcTxnrd2 were up-regulated in both the short-term selenium-reared strain and long-term selenium-reared strain of T. cinnabarinus. Among them, the expression level of TcSPS1 was closely dependent on the selenium concentration. The soluble recombinant protein of TcSPS1 was successfully obtained using the prokaryotic expression system. The specific activity and the Km and Vmaxvalues of the recombinant TcSPS1 were measured to be 2.366±0.046 nmol/mg pro·min, 10.054±0.062 μmol/L and 29.633±1.777 nmol/mg pro·min, respectively. 【Conclusion】 Through the analysis of selenium metabolism pathway genes, the molecular mechanism of the adaptation of T. cinnabarinus to selenium was preliminarily explained, and it was proved that the up-regulated expression of the TcSPS1 gene plays an important function in the adaptation of T. cinnabarinus to selenium.

Key words: Tetranychus cinnabarinus, selenium, selenium metabolism pathway, selenophosphate synthetase, differentially expressed gene, prokaryotic expression, enzyme activity