Sublethal Efffects And Mechanism Of Action Of Benzothiazole To Bradysia Odoriphaga

Bradysia odoriphaga(Diptera: Sciaridae) is the major pest that damages Chinese chive production. In recent years the registration pesticides for control this insect is less and the application technque is not proper, which results in the decrease of the sensitivity of the insect on conventional insecticides, and leaves high residues on marketed Chinese chives. Thus, seeking new effective insecticidal compounds is necessary to substitute the conventional pesticides or to improve their efficacy. To fully understand the potential of benzothiazole for control of B. odoriphaga, in this paper the sublethal effects of benzothiazole on the developmental times, the fecundity and population parameters of B. odoriphaga were studied. The effects of physiological biochemical level were also evaluated and the iTRAQ-based quantitative proteomics analysis was used to investigate the effects of benzothiazole on the proteomic expression profile of B. odoriphaga. The main results were summarized as follow:1. Laboratory investigations showed that sublethal concentrations(LC10 and LC30) of benzothiazole decreased the survival rate and the fecundity of B. odoriphaga compared with control. The intrinsic rate of increase(rm) decreased to 0.1391(LC10) and 0.1140(LC30) day-1 compared with the control population(0.1589 day-1). The net reproductive rate(R0) in the control was 54.39 offspring/individual, whereas the R0 decreased to 41.80 and 25.08 offspring/individual in the LC10 and LC30 treatments, respectively. This study demonstrated that sublethal concentrations of benzothiazole adversely affected the developmental time, fecundity and life table parameters of B. odoriphaga.2. Sublethal concentrations(LC10 and LC30) of benzothiazole significantly reduced the food consumption of the larvae on the second day after treatment(2 DAT). However, there were no significant changes in pupal weight among the different treatments. We also measured the protein, lipid, carbohydrate, and trehalose contents and the digestive enzyme activities of the larvae, and the results suggest that benzothiazole reduced the nutrient accumulation and decreased the digestive enzyme activities of B. odoriphaga. In addition, the activity of glutathione S-transferase was significantly decreased at 6 h after treatment with benzothiazole, whereas general esterase activities were significantly increased at 6 and 24 h after treatment. The results of this study indicate that benzothiazole interferes in the normal food consumption and digestion process by decreasing the activities of digestive enzymes.3. In response to benzothiazole, 92 identified proteins in B. odoriphaga exhibited altered levels of expression, among which 14 proteins were related to the action mechanism of benzothiazole against B. odoriphaga, 11 proteins were involved in stress response and 67 proteins were associated with adaption mechanism of B. odoriphaga to benzothiazole. Further bioinformatics analysis indicated that the reduction of the energy metabolism, inhibition of detoxification process and interference of the DNA and RNA synthesis were potentially associated with the mode of action of benzothiazole. The myosin heavy chain(MyHC), succinyl-Co A synthetase(SCS), polyA-binding protein(PABP) and Ca+-transporting ATPase may be related to stress response to benzothiazole. Increased expression of proteins involved in carbohydrate metabolism, energy production and conversion pathway, amino acid metabolism, lipid metabolism and inorganic ion metabolism were responsible for adaptive response of B. odoriphaga to benzothiazole.