Abstract: 【Aim】 In order to clarify the resistance mechanism of Tetranychus urticae to spirodiclofen at the molecular level. 【Methods】 The full-length cDNAs of GST genes of T. urticae were cloned by RT-PCR, the structure and function of the coded proteins were analyzed by bioinformatic software, and the expression levels of GST genes in the spirodiclofen-resistant (Sp-R) and susceptible (SS) strains of T. urticae were assayed by quantitative real-time PCR. 【Results】 Two GST genes were cloned and named as TuGSTd1 and TuGSTd2, which were deposited in GenBank under the accession no. KC445659 and KC445660, respectively. The open reading frame of TuGSTd1 is 648 bp in length, encoding 215 amino acids with the predicted molecular mass of 24.47 kDa and the theoretical pI of 5.49, while that of TuGSTd2 is 648 bp in length, encoding 215 amino acids with the predicted molecular mass of 24.57 kDa and the theoretical pI of 6.33. Phylogenetic analysis showed that these two GST genes have 93% amino acid sequence identity with Delta class GSTs of Panonychus citri. Quantitative real-time PCR showed that the relative expression levels of TuGSTd1 and TuGSTd2 in Sp-R were 5.60 and 3.75 times as high as those in SS, respectively. 【Conclusion】 The relative expression levels of GST genes in Sp-R were higher than those in SS, suggesting that the up-regulated expression of GST genes is probably related with the development of resistance to spirodiclofen in T. urticae.

Key words: Tetranychus urticae, spirodeclofen-resistant strain, glutathione S-transferase (GST), gene cloning, expression level, real-time fluorescent quantitative PCR