Regulation of the trehalose content in diapausing and non-diapausing pupae of the Chinese citrus fly,
Bactrocera minax (Diptera: Tephritidae)
2018, 61 ( 9):
【Aim】 This study aims to compare the contents of trehalose and glucose, the activities of key enzymes in trehalose biosynthesis and catabolism pathway, and the expression levels of genes encoding these key enzymes among pupae at pre-diapause, diapause, and post-diapause stages, and between diapausing and non-diapausing pupae of the Chinese citrus fly,
Bactrocera minax. 【Methods】 The contents of trehalose and glucose, and the activities of trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP), and trehalase (Tre) in B. minax pupae in pupae at the pre-diapause stage (1 d-old pupae), diapause stage (30, 60 and 90 d-old pupae), and postdiapause stage (120 and 150 d-old pupae) were compared using spectrophotometry, and the expression levels of TPS, TPPB, TPPC-1, TPPC-2, and Tre-1 were determined using quantitative real-time PCR (qPCR). In addition, the neonate pupae were injected with 20-hydroxyecdysone (20E) as the treatment (injected with 10% ethanol as the control), and the contents of trehalose and glucose, the activities of key enzymes and the expression levels of the above genes at 1 and 30 d after injection were compared between the treatment and control groups. 【Results】 When B. minax pupae entered diapause, their trehalose content significantly increased, while their glucose content changed marginally as compared with those of pre- and post-diapause stages. The TPS and TPP activities and the expression levels of TPS, TPPC-1 and TPPC-2 increased gradually after pupation and reached the highest level during the diapause stage, then significantly decreased before adult emergence. The expression level of TPPB did not change significantly throughout the pupal stage. The Tre activity and the expression level of Tre-1 gradually increased after pupation and reached the highest level at the early diapause stage, then significantly decreased, followed by a significant increase before adult emergence. At 1 d after 20E injection, in pupae of the treatment group the contents of trehalose and glucose, the activities of TPS, TPP and Tre, and the expression levels of TPS, TPPC-2 and Tre-1 only changed slightly, while the expression level of TPPB significantly decreased and that of T PPC-1 significantly increased as compared to the control group. At 30 d after injection, in non-diapausing pupae of the treatment group the trehalose content increased significantly, the glucose content, the TPS and Tre activities, and the expression levels of TPS and Tre1 significantly decreased, while the TPP activity, and the expression levels of TPPB and TPPC-2 did not change significantly as compared to those in diapausing pupae of the control group. 【Conclusion】 The trehalose content in B. minax pupae varies with diapause status under the regulation of key enzymes in trehalose biosynthesis and catabolism pathway, displaying the close relationship between trehalose and diapause. The underlying mechanisms, however, need further investigation.
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